Student Questions : Case 2

Which of the following chemokine receptors do activated T cells increase the expression of? A. CXCL8 B. RANTES C. CXCR5 D. CCR7 E. EPO

C. The movement of activated B and T cells relies on the expression of certain chemokine receptors. Activated T cells, which are mentioned in the question, increase the expression of CXCR5 while reducing the expression of CCR7. Increasing CXCR5 expression is important as it goes on to bind to chemokines produced by activated B cells. Activated B cells undergo the opposite change;

Which of the following major histocompatibility complexes does CD4+ T cells bind to? A. MHC-1 B. MHC-2 C. Both MHC-1 and MHC-2 D. MHC-20 E. CD4+ T cells do not interact with MHC at all.

Correct Answer: B. MHC-2 predominantly binds to CD4+ T cells.

Lydia is doing research on the activation of B lymphocytes. As part of her experiment naive mature B cells are exposed to an antigen, resulting in B cell proliferation and differentiation. What two isotypes will the naive B cells express? A. IgA1 and IgA2 B. IgE and IgG C. IgD and IgM D. IgG1 and IgG3 E. IgD1 and IgD2

Correct Answer: C- membrane IgM and IgD are the antigen receptors found on naïve B cells. They are noncovalently associated with the subunits Igα and Igβ and together form the B cell receptor complex (BCR)

A 53-year-old male comes to the office after recovering from surgery. He just had a splenectomy performed due to a thrombosis caused by uncontrollable portal hypertension. What acquired immunodeficiency is a complication of this procedure? A. Metabolic derangement inhibiting lymphocyte maturation and function B. Reduced site of leukocyte development C. Depletion of CD4+ helper T cells D. Decreased phagocytosis of microbes E. Decreased bone marrow precursors for all lymphocytes

Correct Answer: D. Decreased phagocytosis of microbes The spleen is the site where encapsulated microbes are phagocytosed, and the lack of it will result in a higher risk of infection and sepsis for the patient.

Which of the following is NOT a feature of B cell isotype switching? a. The process requires T cell help b. The B cell rearranges constant region - not its variable region c. The B cell can not switch back to original isotype d. The process involves activation-induced cytidine deaminase (AID) e. The process requires at least two B cells to work in tandem

Correct Answer: The correct answer is E. Answers A-D are all true regarding isotype switching while E is incorrect because the only other cell needed for Isotype switching in a B cell is a T cell.

A 46-year-old male of European descent presents to the ER complaining of recurrent respiratory infections and diarrhea. A serum immunoglobulin panel is ordered and the patient subsequently receives a blood transfusion for his condition. However, he passed away shortly after the transfusion. What is the most likely defect that characterizes the patient's condition? A. The patient had an inherited defect in Th17 cells. B. The patient only had IgM antibodies due to a defect in CD40L, which is required for Ig class switching and affinity maturation. C. The patient had low IgA-producing plasma cells due to impaired B lymphocyte differentiation. D. The patient had a mutation in the gene that encoded SAP (SLAM-associated protein). E. The patient had an underdeveloped thymus due to a defect in the third and fourth pharyngeal pouches.

Correct answer - C: The patient had isolated IgA deficiency, which is shown by low levels of IgA antibody. The patient was transfused with blood containing IgA antibody, which was recognized as a foreign antigen by his immune system. As a result, the patient went into anaphylactic shock.

Antigen-activated helper T cells and B cells migrate toward one another as a result of changes in expression of certain chemokine receptors on the activated lymphocytes. This initial interaction between the T cells and B cells occurs at what location? A. Edges of lymphoid follicles B. T cell zone C. B cell zone D. Germinal center E. Both B and C

Correct answer: A. Edges of lymphoid follicles. Antigen-activated helper T cells and B cells migrate towards each other at the edge of the follicles. This is where the initial antibody response develops. Some changes in expression of chemokine receptors include activated T cells reducing expression of chemokine receptor CCR7 and increasing expression of CXCR5

A 6-month old infant presents with her parents to the clinic. Upon physical examination and diagnostic testing, you suspect the patient has SCID. What is the most likely presentation of this infant that led to the diagnosis? A. Thrush, diaper rash, failure to thrive B. Red rash with fluid-filled blisters on one side of the body C. Mouth and nose ulcers with a "butterfly" rash on the face D. Fever, cough, difficulty breathing E. Fever, vomiting, abdominal pain

Correct answer: A. This is the documented physical presentation of an infant with SCID, as described on page 242. Some patients develop a morbilliform rash shortly after birth as well, because the maternal T cells are transferred across the placenta and attack the fetus.

A 59 year old male visits his primary care physician with multiple complaints leading to a diagnosis of a bacterial infection. The physician decides to treat the patient with a sulfonamide. What is the most direct target for this class of medication? a. Dihydrofolate Reductase b. Dihydropteroate Synthase c. Folate receptors d. PABA e. Pteridine

Correct answer: B. Bacteria are unable to take up folic acid from its environment, it must synthesize the vitamin de novo form PABA. By inhibiting Dihydropteroate Synthase the bacteria is unable to synthesize folic acid and prevents bacterial growth.

A 23-year-old female presents to the clinic and is treated for a bacterial infection in her ear. As part of her innate immune response, the complement system is activated and aids in the activation of B cells. In addition to the B Cell Receptor interacting with antigen on the microbe surface, what other receptor/ligand interaction is involved in the activation of her B cells via the complement pathway? A. CR2 / PAMP B. TLR / C3d C. CD8 / bacterial antigen D. CR2 / C3d E.CD20 / PAMP

Correct answer: D. In addition to the interaction between BCR and bacterial surface antigen, the complement component helping in B cell activation is: CD2 (Complement Receptor type 2) receptor present on the B cell surface interacting with the complement protein CD3 which is coating the bacteria.

A newborn child is brought to the Emergency Department after accidentally swallowing sulfonamides. Why are sulfonamides contraindicated in newborn patients? A. Sulfonamides can compete with bilirubin for binding sites on serum albumin and can cause kernicterus in newborns. B. They selectively inhibit parasitic DHFR, which increases likelihood of contracting parasitic infection. C. Sulfonamides are M3 agonists, which cause breathing issues to manifest in newborns. D. The body forms antibodies towards the sulfonamides that cross-react with the newborn's own self antigens. E. Sulfonamides have strong anti-inflammatory effects that lead the newborn prone to increased likelihood of contracting systemic infections.

A - The increase in unconjugated bilirubin that occurs as a result of the competition leads to brain damage (kernicterus) in newborns.

A 73 year old female presents to her primary care physician for follow-up after being diagnosed with a compression fracture of L2 and L3. The fracture occurred secondary to the patient falling and twisting during the fall. Her physician suspects that the patient is suffering from Osteoporosis. What test is required to determine her risk of future fractures? a. Bone mineral density b. X-ray c. CT d. Fracture Risk Assessment Tool e. There is no specific test for osteoporosis, it is a diagnosis based off of ruling out other conditions.

A-Correct. The bone mineral density (BMD) test is the best test to determine fracture risk. A lower BMD indicates a higher risk of fracture.

Max, a 1-year-old infant, presents to the pediatrician with his second bacterial infection. Upon further questioning the pediatrician discovers that Max's two siblings and his mother have a history of recurrent bacterial and viral infections. On suspicion of a primary immunodeficiency disease the physician runs tests and discovers that Max has genetic disease that only affects the classical complement pathway. What complement protein is most likely deficient? A. C2 B. C3 C. C5 D. C6 E. C7

A. Correct - C2 and C4 are early components of the classical pathway but are not a part of the alternative pathway. Often this deficiency is not diagnosed because the alternative pathway is able to produce a sufficient amount of complement.

New parents Chris and Carla bring their two month old baby boy in to see the pediatrician after noticing that he has many white patches on her throat and diaper rash that just won't get better. She also does not sleep soundly and has general failure to thrive. The pediatrician identifies the white patches as thrush, and after more testing, finds that this infant has an X-linked genetic defect, resulting in a mutation in the gamma chain subunit of cytokine receptors. What cells are the most deficient in this patient? A. T-cells B. Platelets C. Macrophages D. Dendritic cells E. Erythrocytes

A. Correct. This is a case of X-linked SCID, as identified in the question stem by the persistent, dramatic candidiasis, failure to thrive, and specified X-linked genetic defect resulting in mutation of the gamma chain subunit of cytokine receptors. Due to this transmembrane protein being mutated, patients with SCID have reduced interleukin levels, particularly IL-7, which is required for T-cell precursor survival.

Upon a visit with his pediatrician, a 4-year-old boy was found to have hypotonia, short stature, hypogonadism, obesity, and small hands/feet. His physician diagnosed him with a genetic disease caused by a deletion on chromosome 15. What is the most likely diagnosis? A. Huntington disease B. Prader Willi Syndrome C. Angelman syndrome D. Fragile X syndrome E. Leber Hereditary Optic Neuropathy (LHON)

B. Correct: Prader Willi is caused by paternal deletion on chromosome 15. The symptoms mentioned in the stem are associated with this disease.

A 5 month old male was recently diagnosed with DiGeorge Syndrome, which is caused by a deletion in 22q11 and results in the failure of development of the thymus. What embryological structures are associated with this disorder? A. Pharyngeal pouch I and IV B. Pharyngeal pouch II & III C. Pharyngeal pouch III & IV D. Pharyngeal pouch V and VI E. Pharyngeal pouch II and V

C. Correct; Pouch III is associated with DiGeorge and forms the inferior parathyroid gland and thymus; Pouch IV is associated with DiGeorge and forms the superior pair of parathyroid glands and ultimopharyngeal body (forms thyroid gland)

A patient comes to her appointment for genetic counseling because she wants to get pregnant someday. She asks the physician whether carrying a female will differ in how much X-linked gene products there are compared to carrying a male. The physician explains that although the female carries two X chromosomes, it will equal the same as a male due to what process that occurs during embryonic development? A. X-inactivation of one X chromosome B. Anticipation C. Imprinting D. Sex- linked mutations E. X- activation

Correct Answer : A. One x chromosome is randomly inactivated early in the embryonic development of females to ensure that both females and males will produce the same quantities of x-linked gene products.

A 25 yo male named Ben Duchenne and his wife Becky are excited for the birth of their son Greg. Unfortunately, as Greg gets older, he experiences unusual clumsiness, and profound muscle weakness. Becky decides to take her son to the pediatrician. Lab tests show a frameshift mutation found in a certain gene that causes a total lack of dystrophin. What are the chances that his father has passed down this condition? A. 0% B. 25% C. 50% D. 75% E. 100%

Correct Answer A: Based on lab tests and symptoms, Greg suffers from Duchenne's muscular dystrophy and not Becker muscular dystrophy. However, Both Duchenne and Becker muscular dystrophy are caused by X-linked recessive mutations. Since father can only pass the Y chromosome to his son, there is 0% Greg received the genetic defect from his father.

Bonita and her friend are finally able to go on their long-awaited trip to Virginia Beach after both being vaccinated against COVID. During the trip, Bonita and her friend develop parasitic infections on their feet due to stepping on Ascaris eggs. What factors are involved in the process that creates the proper antibody class that the immune system uses to get rid of helminthic infections? A. ICOS, CDC, FDIC B. DAG, PKC, IP3 C. CD40L, IL-4, cytokines D. TGF-B, BAFF, CD40L, IFN-y E. CD40L, FDC

Correct Answer C: The infection that Bonita and her friend contracted is a helminthic infection. The immune system uses B cells with IgE heavy chains to fight against parasitic infections since they are too large to be phagocytosed. Eosinophils recognize the Fc portion of the Ɛ heavy chain, which allows them to bind to IgE antibodies.

A 35 yr old male is brought into the ED by EMS for the 5th time in the past 2 months with symptoms of stiff neck, photophobia, seizures and severe headaches. The attending on duty has seen this patient already and knows to take a CSF sample. The results from the CSF shows gram negative diplococci. Since this patient has had recurrent infections with this organism, the physician decides to send the patient to ICU so that the immune system labs can be done. After a few days, it is found that the patient has a deficiency in his complement system which causes these recurring infections. What deficiency does this patient most likely have? A. Deficiency in the components forming the membrane attack complex B. Deficiency of C3 complement protein C. Deficiency of C1 inhibitor D. A deficiency of C2 or C4 complement proteins E. Deficiency of properdin or factor D

Correct Answer Explanation: This patient is suffering from a classic case of Meningitis caused by Neisseria meningitidis. Neisseria bacteria have thin cell walls that make them susceptible to the lytic actions of the membrane attack complex (MAC) formed by terminal complement proteins (C5-9).

A male patient presents to the clinic. He is known to have recurrent infections. Diagnostic imaging and lab work show a normal thymus but a low T cell count in his peripheral blood as well as a recently discovered case of B cell lymphoma. The patient also has a low platelet count. It is soon determined that this patient's condition was genetically inherited. Which of the following is the most likely cause of the patient's disease? A. X-linked agammaglobulinemia B. Wiskott-Aldrich Syndrome C. X-linked hypo-IgM syndrome D. X-linked lymphoproliferative disease E. Isolated IgA deficiency

Correct Answer Explanation: Wiskott - Aldrich Syndrome is the correct answer because a normal thymus with a progressive loss of T cells in the peripheral blood is characteristic of this disease. Patients with this disease are also prone to B cell lymphomas.

John and Larry were interested in learning about how helper T cells and B cells work together in the immune response. However, they forgot what additional aspects along with cytokines are used for communication between both cells. Which ligand do antigen-specific B cells use to communicate with activated helper T cells? a. CD40 b. CD3 c. CD16 d. CD19 e. CD34

Correct Answer: A - CD40L on activated T helper cells bind to CD40 on B cells. This connection generates signals that allow the B cell to release antibodies. This cascade of events causes the stimulation of more B cell production

This is the second time Jimmy has gone to his PCP regarding a sinus infection. The PCP has to explain to Jimmy why he doesn't feel as bad as before. What is the best way to do that? a. Jimmy has more memory B cells that activate IgG and isotope switching, which help reduce the response b. Jimmy has more IgM antibodies that help reduce his symptoms c. Jimmy has more naive B cells in the peripheral lymphoid tissues that proliferate into memory cells d. Jimmy peak response is smaller therefore he experiences less symptoms for a shorter duration e. Jimmy has less IgG antibodies that help reduce his symptoms

Correct Answer: A - This is because, during a secondary response, an individual has more memory cells and IgG antibodies that help increase the peak of the immune response. Then, the individual will not experience the symptoms as severely

A researcher has been using CRISPR to incorporate a gene into a single X chromosome with a goal to genetically engineer babies to become professional athletes. He probed his gene with a fluorescent tag and observed that his gene was placed into a Barr body in somatic cells that contained a 46,XX karyotype. Based on this observed, what genetic mechanism contributed to his designer gene being placed into the Barr body? a. X Inactivation b. Non-penetrance c. Uniparental Disomy d. Genomic Imprinting e. Genetic Anticipation

Correct Answer: A - X inactivation occurs early in female development and serves to provide an equalization of X-linked gene products (Dosage Compensation). X chromosomes that are inactivated are "pushed into the corner" of a cell in the form of a transcriptionally silent Barr body. Since the researcher placed his gene on the X chromosome, and the female somatic cells (46,XX karyotype) showed fluorescence for the gene in the form of a Barr body, X inactivation would be the best answer choice

A female that carries the gene for this disease mates with a male who is normal. They have 4 children, 2 daughters and 2 sons. One of the daughters is normal and the other is a carrier. One of the sons is normal and the other has the disease. The son who has the disease presents with diminished sweating and heat intolerance along with light colored hair, eyelashes and eyebrows. He also has missing teeth. What disease is the son suffering from? A. Hypohidrotic ectodermal hypoplasia B. Vit D-resistant rickets C. Aarskog-Scott Syndrome D. Nephrogenic diabetes insipidus E. Otopalatodigital spectrum disorder

Correct Answer: A- The son is suffering from an X-linked recessive disorder which Hypohidrotic ectodermal hypoplasia is. Additionally, the symptoms presented are directly related to hypohidrotic ectodermal hypoplasia.

A 8 month old male, Prince George, presents to the physician with bruising, severe bleeding from wounds, and hemarthrosis. The physician recognizes the familial disorder and worries about bleeding episodes as well as diminished joint function. His treatment plan includes administering factor VIII concentration into the veins. What is the most likely diagnosis for the disease? a. Hemophilia A b. Hemophilia B c. Duchenne Muscular Dystrophy d. Prader-Willi Syndrome e. Angelman Syndrome

Correct Answer: A. Hemophilia A is caused by mutations in the gene that encodes clotting factor VIII. It is the most common of the severe bleeding disorders and has been recognized as a familial bleeding disorder for centuries. Factor VIII is a key component of the clotting cascade. Fibrin formation is affected, resulting in prolonged and often severe bleeding from wounds and hemorrhages in the joints and muscles. Bruising is often seen.

An expectant mother has just received the results of her amniocentesis. The doctor explains that her child has a mutation in the gene encoding the 𝜷 chain (CD 18) of 𝜷2 integrins. What congenital (primary) immunodeficiency is the doctor describing? A. Leukocyte Adhesion Deficiency Type 1 B. Chronic Granulomatous Disease C. Chediak-Higashi Syndrome D. Toll-like Receptor Signaling Defects E. Leukocyte Adhesion Deficiency Type 2

Correct Answer: A. Leukocyte Adhesion Deficiency Type 1 Leukocyte Adhesion Deficiency Type 1 results from a mutation in the CD18 𝜷 chain of 𝜷2 integrins. This leads to decreased or absent expression of 𝜷2 integrins, which then causes defective leukocyte adhesion to endothelial cells and migration into tissues. You can get recurrent fungal or bacterial infections with this immunodeficiency.

A 5-year-old patient presents to the clinic with complaints of eczema. Upon further testing, it was found that the patient also had reduced blood platelets and immunodeficiency. Based on this information, the physician diagnoses the patient with an x-linked disease. What mutation is present in the disease that the patient is diagnosed with? A. Mutation in a gene that encodes a protein that binds to various adaptor molecules and cytoskeletal components. B. Mutations in a gene whose product is involved in DNA repair C. Mutation in the gene encoding perforin D. Mutation in genes that encode proteins involved in granule exocytosis E. Mutations in transcription factors that normally induce class II MHC expression

Correct Answer: A. Mutation in a gene that encodes a protein that binds to various adaptor molecules and cytoskeletal components. The disease that the patient presents with is Wiskott-Aldrich Syndrome which is characterized by eczema, reduced blood platelets, and immunodeficiency. The X-Linked disease is caused by a mutation in a gene that encodes a protein that binds to various adaptor molecules and cytoskeletal components.

A medical researcher is analyzing B lymphocytes interaction with helper T Cells. She recognizes that 3 signals are necessary for the activation of helper T cells. Which of the following is one of the signals needed? A. Cytokine recognition B. CD60/CD60L C. CD20/ CD20L D. Chemokine recognition E. The entire genome of the foreign invader

Correct Answer: A. The 3 necessary signals are CD40/CD40L, cytokine recognition, and antigen presentation.

The B cell receptor (BCR) complex is able to recognize native antigens, whereas the T cell receptor (TCR) complex can only recognize a single sequence presented to it by MHC. What two proteins are associated with the BCR to aid in signal transduction upon antigen binding? a. Igα and Igβ b. γ and ε c. Igβ and δ d. ε and δ e. Igβ and γ

Correct Answer: A. The BCR complex is noncovalently associated with proteins Igα and Igβ

A baby presents with prominent thrush, extensive diaper rash and a failure to thrive. The physician believes it is an immunodeficiency disease. While genetically testing the baby to determine the disease the parents are also tested. The baby's results were lost in the lab but both parents came back as asymptomatic carriers of the disease. Based on the symptoms and genetic results of the parents, what disease can the doctor infer that baby has? A. Autosomal Recessive SCID B. X-Linked SCID C. Hyper IgM Syndrome D. Isolated IgA Deficiency E. X-Linked Lymphoproliferative Disease

Correct Answer: A. The symptoms listed are the textbook's classic symptoms of a baby affected by SCID. Both parents are carriers, but if it were an X-linked disease and the father was a carrier he would not be asymptomatic which eliminates X-linked SCID and leaves Autosomal Recessive SCID as the only choice

A medical researcher is analyzing B cell activation. She is interested in how the activation of the complement system by a microbe can lead to B cell activation. Which of the following is primarily involved in B cell activation by innate immune signals? A. Microbe becomes coated with C3d binds to CR2/CD21 B. Microbial antigens bind to CD19 C. Microbe becomes coated with C3d binds to BCR D. C3d activates toll-like receptors of B cells E.Microbial antigens bind to CD19

Correct Answer: A. When the complement system is activated by a microbe as part of the innate immune response, the microbe becomes coated with proteolytic fragments, C3d, which binds to complement receptor type 2 [ CR2/CD21]. Engagement of CR2 greatly enhances antigen-dependent activation responses of B cells by enhancing tyrosine phosphorylation of ITAMs.

A 43 year old wrestling icon, John Cena, presents to the urgent care facility with a severe upper respiratory infection that has persisted for over 3 weeks. Mr. Cena claims that his symptoms began shortly after the hulkster, Hulk Hogan, unleashed a can of hulkamania on Mr. Cena at Wrestlemania just 3 weeks prior. Lab workup on the patient revealed severely decreased IgA, IgE and IgG serum levels. Additionally, Mr. Cena's IgM count was significantly elevated. Based on the patient's lab work, what would you as the physician suspect as the reason for why his infection has not yet been cleared. a. Defective isotype switching due to a mutation in CD40L b. Defective innate immunity towards intracellular microbes c. Decreased transcription factor activation of IgA, IgE and IgG d. Bruton Tyrosine Kinase (BTK) mutation leading to the decreased serum Ig levels shown e. The patient's leukocytes most likely had on camouflage shorts preventing the immune system from "seeing" them and recruiting them to the pathogen

Correct Answer: A; Based on the lab work of the patient, Mr. Cena is suffering from Hyper IgM Syndrome. This is an X-linked disease due to a mutation in CD40L. Because of this defect, Th-dependent B cells fail to isotype switch. As a result, IgM is the only immunoglobulin produced (because it is the first once synthesized in response to an infection). Because no other Igs can be made, it is difficult to fight off infections.

A 21-year-old college female presents to her health services clinic on campus with complaints of pelvic pain, increased urge to urinate, and pain upon urination. The on-call doctor diagnoses her with a urinary tract infection. The doctor prescribes her an antibacterial regiment that includes sulfamethoxazole in addition to a folate analogue that selectively inhibits bacterial DHFR and thereby prevents the conversion of DHF to THF. What is the drug that is given with sulfamethoxazole? A. Trimethoprim B. Prednisone C. Azathioprine D. Infliximab E. Pyrimethamine

Correct Answer: A; Trimethoprim is a folate analogue that selectively inhibits bacterial DHFT and prevents the conversion of DHF to THF. Trimethoprim is excreted unchanged in the urine and it can be used as a single agent to treat uncomplicated urinary tract infections. For most infections, trimethoprim is used in combination with sulfamethoxazole.

A 30-year-old female presents to her primary care doctor with symptoms of abdominal pain, nausea and diarrhea after drinking contaminated water from a questionable well during a retreat in the woods. She is diagnosed with a Helminth infection. Which of the following antibody classes is responsible for defense against these parasites and is most likely elevated in the patient's blood? A. IgA B. IgE C. IgG D. IgM E. IgD

Correct Answer: B - IgE is the main antibody class for immunity against parasites; Elimination of helminths is eosinophil-mediated because they are too big to be phagocytosed. IgE antibodies coat the helminths and are subsequently bound by eosinophils.

Protein antigens induce changes in B cells to enhance their ability to interact with T helper lymphocytes, overall creating a stronger immune reaction. To begin this interaction between B and T cells, activated B cells endocytose protein antigen that binds to the BCR. The protein antigen is then degraded and processed to be presented on the B cell surface for CD4+ T helper cells to recognize. What will the processed antigen peptide be bound to on the B cell surface in order to be presented for the CD4+ T helper cell? A. IgM B. MHC Class 2 C. MHC Class 1 D. CD19 E. CD40 Ligand

Correct Answer: B - MHC Class 2. Activated B cells endocytose protein antigen that binds specifically to the BCR, which is then degraded and processed. The antigen processed peptide will be bound to MHC class 2 molecules in order to be recognized by the T helper cells (CD4+).

It is known that activated B cells induce the further activation of T cells and their differentiation into Tfh cells. In order for a T cell-dependent antibody response to develop fully, the B cells, together with the Tfh cells, migrate into _______ and form ______? A. T cell zone; germinal centers B. Follicles; germinal centers C. Follicles; antigens D. T cell zone; antigens E. Follicles; vesicles

Correct Answer: B - T and B lymphocytes independently recognize the antigen in different regions of peripheral lymphoid organs and are activated. The activated cells migrate toward one another and interact at the edges of lymphoid follicles.

An infant is born with a large tongue, creases on their ear lobe, and an omphalocele. A physician diagnoses him with an overgrowth disorder caused by imprinting in the human genome. Which of the following are typically associated with this disorder? A. Seizures and ataxic gait B. Wilms tumor and hepatoblastoma C. Hypogonadism and obesity D. Hemarthroses and intracranial hemorrhages E. Clumsiness and muscle weakness

Correct Answer: B - This infant is diagnosed with Beckwith-Wiedemann syndrome. This condition is described as an overgrowth disorder caused by imprinting in the human genome and patients can present with a large gestational weight, large tongue, creases on the ear lobe and an omphalocele. Patients with this condition are predisposed to developing two specific types of cancers: Wilms tumor (a kidney cancer) and hepatoblastoma (a liver cancer).

Sam Malone, a bartender, nervously awaits his upcoming appointment with a genetic counselor. He is scared because Huntington disease runs in his family and his dad who is only 43 years old just started showing signs/symptoms, which are greater in severity than Sam's grandfather who presented with the disease at 55 years old. What is the correct term for the phenomenon occurring in Sam's familial disease inheritance? A) X-linked B) Anticipation C) Imprinting D) Heteroplasmy E)X-Inactivation

Correct Answer: B, Anticipation- describes the observation of some genetic diseases seeming to display an earlier age onset and/or more severe expression in more recent generations of a pedigree

A medical researcher is studying the immune system and its various processes. He is particularly interested in the process by which the affinity of antibodies produced in response to a protein antigen increases with prolonged or repeated exposure to that antigen. This process is known as? A. Somatic Hypermutation B. Affinity Maturation C. Gene rearrangement D. Isotype Switching E. Anergy

Correct Answer: B. Affinity maturation is the process by which the affinity of antibodies produced in response to a protein antigen increases with prolonged or repeated exposure to that antigen. Because of affinity maturation, the ability of antibodies to bind to a microbe or microbial antigen increases if the infection is persistent or recurrent.

A 45-year-old male presents to a new primary care physician after recently moving to California. The patient explains to his new physician that he has a history of AIDS but was never placed on antiretroviral drugs. Which of the following is the patient least likely to develop as a complication to his untreated AIDS? A. Pneumocystis jiroveci B. Mycobacterium tuberculosis C. Intracellular microbes D. Nontuberculous mycobacteria E. Herpes

Correct Answer: B. Mycobacterium tuberculosis Because the patient is not being treated for his AIDS with antiretroviral drugs, the patient is at risk of developing several other infections. Mycobacterium tuberculosis is not something this patient would develop secondary to his AIDS infection.

Carol is studying for her upcoming pharmacology exam and is making a list of medications and their clinical applications. Which of the following is incorrect? A. Methotrexate - carcinomas, psoriasis, rheumatoid arthritis, early stage ectopic pregnancy B. Dapsone - leprosy, dermatitis herpetiformis, Pneumocystitis carinii pneumonia C. Trimethoprim - toxoplasmosis, malaria D. Sulfonamides - vaginal infections, toxoplasmosis, Pneumocystis carinii pneumonia, shigellosis, traveler's diarrhea, UTI, acute otitis media E. Pyrimethamine - toxoplasmosis, malaria

Correct Answer: C Pyrimethamine is used for toxoplasmosis and malaria, Trimethoprim is used for UTs and in combination therapy with sulfamethoxazole. The other answer choices are matched correctly.

A 32-year-old female patient presents to the ED with complaints of fever, joint pain, and "butterfly rash" on the face. Based on her symptoms, polymorphisms in the gene encoding of what receptor is associated with her disease? a. FcRn b. CD21 c. FcᵧRIIB d. CD40 e. FcεRI

Correct Answer: C - FcᵧRIIB is responsible for delivering inhibitory signals that shut off antigen receptor-induced signals, thereby terminating B cell responses. This process is known as antibody feedback which serves to terminate humoral immune responses once sufficient quantities of IgG antibodies have been produced.

A child presents with features including hypotonia, short stature, intellectual disability, and hypogonadism. These features can be attributed to a disease caused by an inherited deletion on paternal chromosome 15 or due to maternal uniparental disomy. What is the disease? a. Leber Hereditary Optic Neuropathy b. Rheumatoid Arthritis c. Prader-Willi Syndrome d. Duchenne Muscular e. Dystrophy Hemophilia A

Correct Answer: C - Prader-Willi Syndrome. P-W syndrome presents with short stature, hypotonia, small hands/feet, obesity, intellectual disability, and hypogonadism. It is caused by a deletion on paternal chromosome 15, which prevents a gene product from being produced. Additionally, P-W can be caused by maternal uniparental disomy, where there would also be a missing paternal chromosome segment

Hamilton, a 5-year-old male has been brought to the clinic with a fever, cough, and shortness of breath. It was mentioned that Hamilton frequently gets infections. Further testing was performed and it was determined that Hamilton's infection was caused by Pneumocystis jirovecii. Lab results show Hamilton has elevated levels of IgM and no presence of IgA or IgE. A genetic test was also ordered to confirm the underlying cause of Hamilton's condition and it was determined there was a mutation on the gene encoding CD40L. Which one of the following choices is not a possible mechanism causing Hamilton's condition? A. CD40L mutations prevent proper CD40L-mediated macrophage activations B. Defective CD40L prevent the interaction between B cells and T cells to trigger B cell Ig class switching C. Mutation in cytoplasmic tyrosine kinase D. Defective CD40L prevent the affinity maturation of B cells E. Mutation of the gene located on Xq26, interfering with proper CD4+ T cells functions and interactions

Correct Answer: C, Hamilton's symptoms are caused by hyper IgM syndrome. Patients with the syndrome typically present with infections concurrent with fever. Their lab results also show higher levels of IgM while deficient in IgA, IgG, and IgE antibodies. The underlying mechanism is due to defective CD40L on the antigen activated T cells or a problem with the B cells

Peyer, an 8-month-old male has been brought to their primary care physician with complications of recurrent respiratory tract infections. Expansive testing was performed and it was determined that Peyer's infection was caused by Streptococcus pneumoniae. Other testing performed also noted that while Peyer had normal T-cell activity, both B-cells and plasma cells were absent, genetic testing was also performed and it was determined that the condition was brought on by a mutation in a tyrosine kinase of the long arm of the X chromosome. Which of the following conditions below would best explain the lab results discussed above? A. X-linked lymphoproliferative disease B. DiGeorge syndrome C. X-linked agammaglobulinemia D. X-linked SCID E. Hyper-IgM syndrome

Correct Answer: C, X-linked agammaglobulinemia is shown by a failure of B-cell precursors to develop into mature B-cells. This is due to a tyrosine kinase (Bruton tyrosine kinase) mutation on the long arm of the X chromosome at Xq21.22. This causes inhibition on light chain rearrangement, arresting maturation of the B-cell. Due to being an X-linked disorder, X-linked agammaglobulinemia is almost exclusively in males and is marked by recurrent bacterial respiratory tract infections with both B-cells and plasma cells being absent.

Magic Johnson was diagnosed with HIV at the time when its nature was not fully understood. He has survived for so long from having early access to antiretroviral therapy, which is now the standard treatment of HIV. Which of the following was the most likely target in the treatment used? A. A protein that activates CD4+ T cells B. A cytokine released by activated T cells C. An enzyme involved in viral replication D. A phospholipid found in the cell membrane E. A cytokine that stimulates lymphoid progenitor cell proliferation

Correct Answer: C. An enzyme involved in viral replication The question implies that Magic Johnson was most likely taking what is now the standard treatment of HIV. Part of standard treatment involves antiretroviral therapy, which is currently aimed at targeting viral replication, making reverse transcriptase a prime target in this treatment.

A 36-year-old bisexual male is diagnosed by his physician with a positive sense RNA virus that was acquired via sexual intercourse. After infection with the virus, the prodrome of symptoms that can occur in the acute viremia phase include all the following except? A. Fever B. Body aches C. CD4+ count <200 cells/mm3 D. Cervical lymphadenopathy E. Pharyngitis

Correct Answer: C. CD4+ count <200 cells/mm3 The positive sense RNA virus that the patient was infected with is human immunodeficiency virus (HIV). This virus can be acquired via sexual intercourse, sharing contaminated needles, transplacental transfer, or transfusion of infected blood. The correct answer is CD4+ count <200 cells/mm3 because this does not occur in the acute viremia phase, immediately after infection with the virus.

X-Linked Severe Combined Immunodeficiency accounts for over 50% of all SCID cases. Patients with this form carry a mutation in the common γ-chain (γc) subunit of cytokine receptors for many immunomodulating interleukins. Which of the following is correct regarding the interleukins associated with this form of SCID? A. IL-7 signaling is required for the proliferation of mast cells B. X-linked SCID causes IL-5 deficiency, which leads to a significant reduction in eosinophil number C. IL-15 is important for the maturation and proliferation of NK cells D. Without IL-7, B cell cannot produce antibodies due to impaired B-cell development E. IL-11 is directly associated with survival and proliferation of lymphoid progenitor

Correct Answer: C. IL-15 is important for the maturation and proliferation of NK cells, and because the common γ chain is a component of the receptor for IL-15, these individuals often have a deficiency of NK cells as well.

A researcher wanted to further educate the public on the functions of helper T lymphocytes towards humoral immune responses. During his research, the researcher studied interactions between helper T cells and B cells. He studied how each were activated. Which of the following areas are naïve CD4 T cells activated? A. Follicles of lymphoid organs B. Germinal Centers C. T cell zone in secondary lymphoid organs D. Dark zone E. Light Zone

Correct Answer: C. Naïve CD4 T cells are activated in the T cell zone in secondary lymphoid organs by antigen. The antigen is presented by dendritic cells, and naïve CD4 T cell differentiates into Helper T cells. From there, the Helper T cell will be able to migrate towards the B cell to stimulate proliferation and differentiation.

Charles DiGeorge is 15-year-old that has a defect in his lymphocyte maturation. This defect is characterized by a deletion on chromosome 22 that impedes the development of the parathyroid glands & thymus. Which lymphocyte is affected? A. B lymphocyte B. B & T lymphocytes C. T lymphocyte D. Neutrophils E. Natural Killer Cells

Correct Answer: C. T lymphocyte Charles DiGeorge has DiGeorge Syndrome which is characterized by a defect in T cell maturation. It causes a deletion on chromosome 22 that interferes with the parathyroid glands and the thymus that usually improves with age.

A 19-year-old male has a persistent infection that is recovering but at a slow pace. As the infection persists, the amount of available antigen in the patient slowly decreases but certain B cells are still able to strongly bind at lower concentrations to produce antibodies through a process called affinity maturation. Which of the following below correctly describes the area in a lymphocyte, where this process takes place? a. High Endothelial Venule b. T-cell area c. Germinal centers d. Medullary cords e. Efferent lymphatic vessels

Correct Answer: C. The key to answering this question is knowing that affinity maturation is the result of somatic hypermutations of immunoglobulin genes in dividing B cells. The B cells that have a high affinity after these hypermutations will be positively selected and this is the reason that they can produce antibodies while the concentration of infectious antigen decreases.

A 65-year-old female presents to her primary care physician for her yearly checkup. During the appointment, the physician asks the patient if she would like to receive the pneumococcal vaccine to help protect against pneumonia. The pneumococcal vaccine is a conjugate vaccine that combines a weak antigen with a strong antigen in order to activate a T-dependent response. This provides a stronger and more specific immune response. What type of antigen is needed to produce a T-dependent response in a conjugate vaccine? A. Hapten B. Polysaccharide C. Peptide D. Nucleic Acid E. Lipid

Correct Answer: C. There are two types of humoral immune responses, T-independent and T-dependent. T-independent responses result from B cells interacting with non-peptide antigens. This causes a weaker immune response with low-affinity antibodies producing mostly IgM. T-dependent responses result in a stronger and more specific immune response with isotype switching and affinity maturation.

A 23-year-old male's mother was recently diagnosed with HIV, and he decided that he wanted to educate himself more about the virus. He recently learned that the HIV-1 genome consists of many different genes that encode for proteins that all have separate functions. Which of the following genes from the HIV-1 genome encodes for a protein that promotes the arrest of the cell cycle and enhances integrated viral DNA transcription? A. nef B. rev C. tat D. env E. gag

Correct Answer: C. tat The gene "tat" encodes for the Transcriptional activator (p14) protein that promotes cell cycle arrest and enhances integrated viral DNA transcription.

Sulfa drugs, such as sulfamethoxazole and sulfadiazine, are used to inhibit bacterial synthesis of folic acid. Bacteria must perform synthesis of folic acid as they are not able to absorb the molecule from the environment. Which of the following does not require folic acid synthesis? a. Purines b. Pyrimidines c. Cholesterol d. Amino acids e. DNA

Correct Answer: C; Folic acid is essential for both humans and bacteria, and is in turn used to form purines, pyrimidines, and certain amino acids. Cholesterol is not formed from folic acid in either humans or bacteria.

A 2-year-old male is brought to his pediatrician because his parents are concerned that he has not yet begun to walk. They note that he has had a few upper respiratory tract infections, but nothing they were too concerned about. During the physical examination, the pediatrician notes ataxia, discoloration of skin, and enlarged blood vessels. Following the examination, a serum immunoglobulin test was performed, which came back with low levels of IgA and IgG2, along with elevated levels of IgM. Which of the following correctly pairs the child's diagnosis with the affected gene? A. Wiskott-Aldrich Syndrome; WASP gene B. DiGeorge Syndrome; TBX1 gene C. Ataxia Telangiectasia; ATM gene D. Isolated IgA Deficiency; gene unknown E. X-Linked Lymphoproliferative Disease; gene encoding SAP protein

Correct Answer: C—Ataxia telangiectasia is characterized by abnormal gait, vascular malformations (large dilated vessels), neurological deficits, increased risk of tumors, and immunodeficiency. The most prominent characteristic is the defective production of isotype-switch antibodies, IgA and IgG2, which is the big give away in the question stem.

Which of the following is NOT an outcome of a B lymphocyte activation? A) Development into memory B lymphocytes B) Secretion of antibodies C) Isotype switching D) Antigen recognition E) Affinity maturation

Correct Answer: D - Antigen recognition is the first step in activating the humoral immune response, not an outcome of the B lymphocyte activation. Recognition of antigen triggers signaling pathways that initiate B cell activation. The activation of B lymphocytes results in their proliferation, clonal expansion, and then their differentiation into plasma cells.

A 17 year old patient presents to the clinic for a sore throat and pain while swallowing. The physician diagnoses the patient with pharyngitis and prescribes an antibiotic. The patient, who is a pre-med student, asks about antibody development and his physician informs him that specific antibodies are generated with T cell help. Which of the following Cluster of Differentiation markers is necessary for B cell and T cell interaction? a. CD16 b. CD56 c. CD34 d. CD40 e. CD18

Correct Answer: D - B cells and T cells interact via the MHC and CD40 markers on the B cell and the TCR and CD40 ligand markers on the T cell. Once these two pairs have interacted, the T cell secrete cytokines to influence B cell differentiation.

A 10-yr old male of European descent presents to his ophthalmologist, for a routine eye exam. This is the first eye exam he has ever taken. During the examination, the patient has trouble on the Ishihara color test. He explains to the physician that for as long as he can remember, he's had trouble differentiating between different shades of red. Which of the following forms of color-blindness does this patient most likely have? A) Deuteranopia B) Protanopia C) Deuteranomalous D) Protanomalous E) Rod monochromacy F) Blue cone monochromacy

Correct Answer: D - Protanomalous color-blindness is characterized by the inability to differentiate different shades of red. Trichromatic is the normal human color-vision, as humans have three types of cone cells: red, blue, and green. Dichromacy is when one of those cone cells doesn't function as well as the others. Dichromacy is X-linked recessive. The suffix -anopia usually indicates the total inability to perceive one color, whereas the suffix -anomalous indicates the inability to distinguish different shades of a color

A pregnant woman comes into the clinic for an ultrasound. Upon observation, the doctor sees that the fetus has congenital defects around the heart & great vessels. The worried woman decides to get an amniocentesis, which reveals that the baby has DiGeorge Syndrome, otherwise known as Thymic Hypoplasia. Which of the following immune cells are directly affected by DiGeorge Syndrome? A. B cells B. NK cells C. Macrophages D. T cells E. Eosinophils

Correct Answer: D, DiGeorge Syndrome is a T-cell deficiency that results from failure of development of the thymus. During development, the third & fourth pharyngeal pouches do not develop normally leading to the underdevelopment of the thymus. In a healthy individual, T cells mature in the thymus, which is why in this disorder, there is a loss of T-cell mediated immunity.

The process of helper T cell-mediated B lymphocyte activation is analogous to the process of cell-mediated macrophage activation in cell-mediated immunity. What must a B cell and activated helper T-cell express, respectively, to lead to B-cell proliferation and differentiation? A. CD28, CD28L B. CD40L, CD40 C. CD80/86, CD28 D. CD40, CD40L E. CD28L, CD80/86

Correct Answer: D. A CD40L expressed on a T-cell will bind to CD40 expressed on a B lymphocyte. Engaging CD40 generates signals in a B-cell that stimulate proliferation, differentiation, and the formation of memory B-cells.

A 62-year-old female is brought to the emergency department by ambulance after being shot. She has a medical history of lupus, rheumatoid arthritis, and numerous past respiratory and urinary tract infections. The attending physician makes note of her blood type and orders a blood transfusion. Shortly after the patient has a severe anaphylactic reaction but luckily survives. What was the cause of this reaction? A. The bullet was still in the patient and caused the reaction. B. IgG antibodies from the blood transfusion acted as a foreign antigen. C. The wrong blood type was given. D. IgA antibodies from the blood transfusion acted as a foreign antigen. E. IgE antibodies from the blood transfusion acted as a foreign antigen.

Correct Answer: D. Based on the patient's medical history it should be recognized that the patient has isolated IgA deficiency due to the past medical history of lupus, RA, and numerous infections in mucosal areas. Due to this, D is the correct answer because IgA antibodies from a transfusion can cause anaphylactic reactions.

A 27 year old male presents to the ER complaining of fever, loss of taste, and shortness of breath for 5 days following a trip to Miami. The patient is tested and found to be positive for COVID-19. The patient states that this is his second time being infected with COVID-19. Which of the following is true regarding the humoral response taking place? A. Naive B cell are quickly activated and secrete IgG B. Selectin allow leukocyte navigation and entry to the site of infection C. Activation of the anticipatory response D. Increased IgG with antibodies of higher affinity E. T-independent response occurs since affinity maturation is no longer needed

Correct Answer: D. Secondary exposure allows for an increased heavy-chain isotype switching and affinity maturation, this results in a large quantity of high affinity IgG antibodies being produced in a short period of time.

A 7-year-old female patient is brought into the clinic with her mother after she contracted an infection at school. This is the patient's first exposure to this microbe. The physician informs her mother that the infection should be cleared within 5-10 days. However, after the patient recovers from the initial infection, she returns to school, and is reinfected with the same microbe as before. However, the infection clears after 2 days, much quicker than the original infection. Why was the patient able to get rid of the infection faster after a second exposure? A. T-cell independent antigens B. Release of IgM antibodies C. BCR complex D. Somatic hypermutation of Ig genes E. Presence of B-1 cells

Correct Answer: D. The reason why the patient had a faster immune response after the second infection was due to affinity maturation. Affinity maturation is a result of somatic hypermutation of Ig genes in dividing B cells. This allows for the generation of different B cell clones with varying affinities to the antigen in the initial response.

Heavy-chain isotype switching is induced by a combination of CD40L-mediated signals and cytokines. In the absence of this interaction, B cells are not able to isotype switch. There is a specific syndrome that is caused by mutations in the CD40L gene, leading to production of nonfunctional forms of CD40L in males who inherit the mutation. As a result of this syndrome, which serum antibody is elevated in patients? A. IgE B. IgD C. IgA D. IgM E. IgG

Correct Answer: D. The syndrome the question is referring to is X-linked hyper-IgM syndrome that is caused by mutations in the CD40L gene that prevent heavy-chain isotype switching because it relies on the combination of CD40L-mediated interaction with cytokines. It is located on the X-chromosome.

A 4-year-old boy is brought to his PCP by his parents. The boy had been diagnosed with a fungal infection 1 week ago as he had a persistent fever and breathing issues. The patient's bronchoalveolar lavage smear demonstrated cysts of the suspected organism and methenamine silver staining was done to confirm the diagnosis. The doctor suspects that the patient's susceptibility for this infection may be due to a form of immunodeficiency, characterized by mutations in the gene coding for CD40L. What immunodeficiency disorder does this patient most likely have? A. DiGeorge syndrome B. Common variable immunodeficiency (CVID) C. Hemophagocytic lymphohistiocytosis (HLH) D. X-linked hyper-IgM syndrome E. X-linked SCID

Correct Answer: D. X-linked hyper-IgM syndrome. The vignette describes an infection caused by Pneumocystis jiroveci. X-linked hyper-IgM syndrome is caused by mutations in the X chromosome gene encoding CD40L - a helped T cell protein that binds to CD40 on B cells, dendritic cells and macrophages. This disease leads to defective humoral immunity, characterized by little Ig isotype switching and no affinity maturation. Boys with this immunodeficiency are susceptible to infection by Pneumocystis jiroveci.

Stephen Lin is a DO/PhD student researching parasitic infection treatment in a laboratory. His goal is to develop a new treatment for Pneumocystis jirovecii pneumonia. He knows that PCP impacts the immunocompromised and thinks it is important to combat pathogenic drug resistance. Trimethoprim is a folate analogue that prevents conversion of DHF to THF. During his research he finds that DHFR inhibitors are not frequently used as monotherapy, but rather used synergistically with other agents that inhibit the enzyme dihydropteroate synthase. Which inhibitor of dihydropteroate synthase is most frequently used in conjunction with Trimethoprim? A. Methotrexate B. Sulfanilamide C. Pyrimethamine D. Sulfadiazine E. Sulfamethoxazole

Correct Answer: E - (TMP/SMX). Trimethoprim is a DHFR inhibitor that can be used in monotherapy, but is typically used with sulfamethoxazole. Sulfamethoxazole is a PABA analogue that inhibits dihydropteroate synthase. This specific drug treatment where sulfonamides and DHFR inhibitors are used synergistically to block the production of tetrahydrofolate is referred to as "Sequential Blockade."

A 54-year-old male presents to his physician for the second time in two weeks. On the first visit the man presented with lesions all over his body and was diagnosed with leprosy. He was then prescribed a drug to help treat the leprosy. The patient on his second appointment now is showing side effects to the drug, including weakness, dark colored urine, and yellowish skin. What drug did the physician prescribe to treat his leprosy? A. Trimethoprim B. Pyrimethamine C. Sulfamethoxazole D. Methotrexate E. Dapsone

Correct Answer: E - Dapsone is the correct drug here. First dapsone is a drug used to treat leprosy. Secondly, the symptoms shown of the adverse effects of the drug point to hemolytic anemia which is a serious adverse effect of dapsone.

Brandon, a 22 year old graduate student engages in a conversation with his family physician at a local Hoss's restaurant. His physician tells him how important it is to get the SARS-COVID-19 vaccine during the current pandemic, but Brandon is hesitant because he feels his body is "already strong enough" since he's "already had the flu." While given ample time over dinner, the physician begins to explain the process of humoral immunity. Which of the following correctly describes the process of humoral immunity? A. Non-proteinaceous antigens elicit T-dependent B-cell antibody response B. Proteinaceous antigens elicit T-independent B-cell antibody response C. Antibody class switching is dependent on modifying the antibody's light chain D. T-cells are always required for B-cell antigen binding E. IgM and IgD function as receptors for antigens that initially bind naïve B cells

Correct Answer: E - IgM and IgD are the only immunoglobulins expressed first by a naïve B cell. All other immunoglobulins arise only after B-cell activation via Antibody class switching or from maternal circulation.

A patient presents to her primary care physician with painful urination and thick, white vaginal discharge. This is the patient's third visit for recurrent infections. The physician believes the patient may suffer from an immunodeficiency related to mutations in genes encoding subunits of NADPH oxidase. Which of the following diseases is most likely associated with this enzyme deficiency? A. Leukocyte Adhesion deficiency B. Chediak-Higashi Syndrome C. DiGeorge Syndrome D. Severe Combined Immunodeficiency (SCID) E. Chronic Granulomatous Disease

Correct Answer: E. Chronic Granulomatous Disease The patient presents with an opportunistic Candida albicans infection due to an immunodeficiency as determined by her recurrent visits. Chronic granulomatous disease is caused by mutations in genes associated with NADPH oxidase.

Which of the following is not a functional consequence of antigen binding and cross-linking of membrane immunoglobulins on naive B lymphocytes? a. Interaction with helper T cells b. Responsiveness to cytokines c. Antibody secretion d. Increased survival and proliferation e. Migration from the T cell zone to the follicle

Correct Answer: E. This is false because antigen binding would increase CCR7 expression causing migration from the follicle to the T cell zone, not vice versa.

A young male has been recently diagnosed with a condition impacting the gene FMR1. What would be common physical characteristics this patient may present with? a. Asymmetrical overgrowth of a limb b. Obesity and short stature c. Leg length discrepancy and small triangular shaped face d. Severe bleeding from wounds e. Large ears, long face, hypermobile joints

Correct Answer: E. This patient has fragile X syndrome which occurs from the disease-causing gene FMR1. Fragile X syndrome is typically associated with intellectual disability, large ears, long face, hypermobile joint, or macroorchidism.

A 47 year old male presents to his primary care provider for a routine check-up concerning his HIV progression. The patient is currently undergoing combination antiretroviral therapy, which has been effective in controlling the disease. What immune cell type will the physician continue to monitor as an indicator for the patient's disease progression? A. Anti-HIV antibodies B. CD4+ T cell C. Follicular Helper T cells D. CD8+ cytotoxic T lymphocytes E. Macrophages

Correct Answer: HIV infects cells of the immune system - mainly CD4+ T lymphocytes. HIV causes progressive destruction of these cells and the fall in blood CD4+ T cell count remains the most reliable indicator of disease progression. As the CD4+ T cell count falls, various opportunistic infections are associated with the progressive immune deficiency.

A 5-year old boy presents to his pediatrician's office with fever and difficulty breathing. The physician reviews the patient's history and notices abnormally frequent pyogenic infections so begins to suspect he may have an underlying immunodeficiency. After discussing family history, the physician believes the mutation is inherited in an X-linked recessive fashion. Immunoglobulin testing reveals: normal IgM but markedly reduced IgG, IgA, and IgE. What is the most likely cause for the boy's immunodeficiency? A. Common Variable Immunodeficiency (CVID) B. Hyper-IgM Syndrome C. Severe Combined Immunodeficiency (SCID) D. IgA deficiency E. DiGeorge Syndrome

Correct Answer: Hyper-IgM syndrome is most often inherited in an X-linked recessive fashion, therefore more commonly presents in males. Defective, or absent, CD40 ligands (CD40L) on T-helper (CD4+) cells prevent B cell isotype (class) switching; consequently, B cells are only able to secrete antibodies in the form of their default surface marker, IgM. Due to this immunodeficiency, young patients present for care because of increased susceptibility to opportunistic infections, including Pneumocystis, Cryptosporidium, and cytomegalovirus (CMV).

A 6-month-old male was brought to the pediatrician by his mother due to his extensive diaper rash and white patches in his mouth concerning for oral candidiasis. He was diagnosed with an immunodeficiency involving adenosine deaminase (ADA). What immunodeficiency was the child diagnosed with? A. Leukocyte adhesion deficiency I B. Autosomal recessive SCID C. X linked agammaglobulinemia D. DiGeorge syndrome E. Wishkott-Aldrich syndrome

Correct answer B: Infants affected with SCID present with prominent thrush, extensive diaper rash and failure to thrive. They are extremely susceptible to infections (including candidiasis). The most common cause of autosomal recessive SCID is a deficiency of the enzyme adenosine deaminase (ADA)

After antigen binds to the membrane and crosslinking of membrane Ig occurs, which of the following is not a functional consequence of receptor mediated B cell activation? A.) Increased proliferation and survival B.) Antigen presentation and Interaction with helper T cells C.) Increased expression of cytokine receptors and subsequent responsiveness to cytokines D.) Decreased CCR7 expression E.) Generation of plasma cells and antibody secretion

Correct answer D: Activated B cells decrease CXCR5 expression, increasing CCR7 expression( the exact opposite of activated T cells). As a result activated B and T cell migrate towards one another and meet at the edges of lymphoid follicles.

A male and female couple present to the clinic for genetic testing. The male has a disorder affecting factor VIII. If the female is homozygous normal, what would be the chances of the couple having affected children? A - 0% of daughters will be affected and 100% of sons B - 100% of daughters will be affected and 50% of sons C - 50% of daughters will be affected and 0% of sons D - 50% of daughters will be carriers and 50% of sons will be affected E - 100% of daughters will be carriers and 0% of sons will be affected

Correct answer E - the father has hemophilia A which is an X-linked recessive disorder. The father will pass on the disorder to all female children and no male children. The disorder is recessive so the daughters will be phenotypically normal because their second X-chromosome will produce a normal factor VIII.

A mother brings in her 10-month-old son for his usual checkup today. Upon observation, you notice his mouth remains open for the entire visit and has a triangular shape. The mother has a narrow face and isn't showing much expression. You notice the child's muscle strength is poor and when you test his reflexes, his leg does not relax after contracting. You decide to order genetic testing for this family to confirm your suspicions, and the test confirms a mutation in DMPK, leading to a diagnosis of myotonic dystrophy. Why does the mother show fewer features than her son, who is exhibiting many features of this disease? A. Myotonic dystrophy exhibits anticipation and successive generations inherit more expanded repeats B. Myotonic dystrophy has an autosomal dominant inheritance pattern C. Myotonic dystrophy has an autosomal recessive inheritance pattern D. Severity of Myotonic dystrophy is random throughout generations E. The mother had a difficult pregnancy and childbirth

Correct answer is A. Myotonic dystrophy is a classic example of anticipation, which is a pattern of inheritance where successive generations exhibit more severe expression of the disease at an earlier age than the previous generation. With myotonic dystrophy, the severity of the disease directly correlates with the number of expanded CTG trinucleotide repeats, and with this disease, as you progress through the generations, more repeats are inherited, and the disease is more severe.

For affinity maturation to occur, there will be a point mutation most commonly located in the antigen-binding hyper variable region. This is all in efforts to enhance antibodies and their ability to bind to foreign protein and rid the body of the invader even at low concentrations. What is the name and function of the major enzyme that plays a role in this type of mutation? A. AID, converts thymine to uracil B. AID, converts cytosine to uracil C. AID, converts cytosine to guanine D. Endonuclease, converts cytosine to uracil E. Endonuclease, converts uracil to cytosine

Correct answer is B. The enzyme AID, which is also required for isotype switching, plays a very important role in somatic mutation. This enzyme will convert cytosine to uracil which often times is replaced by thymidine during DNA replication creating a C-to-T mutation, or it can be removed by some error mechanism that will most likely introduce a new base and nucleotide into the strand. Then the B cell that has the most optimal affinity will survive.

A 4-year-old child is brought to his primary care physician by his parents. The parents inform the physician that their child seems to have difficulty standing, complains of muscle weakness, and recently developed a learning disability. After examining the child and observing pseudohypertrophy of the calves, the doctor orders a blood test to confirm his diagnosis. Which enzyme would be present in high levels in the patient's blood for the suspected disease? A. Creatine kinase (CK) B. G6PD C. Alanine aminotransferase (ALT) D. Amylase E. C reactive protein (CRP)

Correct answer: A - According to the symptoms mentioned, the patient is suffering from DMD (Duchenne's Muscular Dystrophy) and symptoms are usually seen before the age of five in children. As the muscle cells die, the enzyme creatine kinase (CK) leaks into the bloodstream. In DMD patients, serum CK is elevated at least 20 times above the upper limit of the normal range.

A patient presents to the ER with destructive bacterial pneumonia. It is determined that this is the result of a defect in an adaptor protein involved in TLR signaling. In which of the following is the defect most likely present: A. MyD88 B. TLR3 C. Fucosyl transferase D. LYST E. gp91phox

Correct answer: A - MyD88 is an adaptor protein found downstream of multiple TLR's. Defects in MyD88 are associated with destructive bacterial pneumonia.

A researcher working in a lab with B cells is curious as to what would happen if she introduced an antigen to the cells. After some time, she observes multiple different changes to the B cell resulting in different functional consequences. What functional consequence did she not observe? A. Affinity maturation B. Increased survival, proliferation C. Responsiveness to cytokines D. Migration from follicle to T cell zone E. Interaction with helper T cells

Correct answer: A - The researcher would not see affinity maturation as a functional consequence of B cell activation by antigens. She would see affinity maturation as a response to helper T cell interaction.

A group of researchers are investigating the mechanisms responsible for the physiologic decline of the humoral immune response over time. They discovered that cells terminate humoral immune responses once enough IgG antibodies have been produced. Which of the following mechanisms is used to shut off antibody production? A. Secreted antibodies form immune complexes with residual antigen and engage FcγRIIB receptor on B cells. B. The binding of multivalent antigen cross-links B cell antigen receptors of specific B cells. C. B lymphocytes display class II MHC-associated peptides for recognition by CD4+helper T cells. D. Helper T cells are activated to express CD40 ligand (CD40L) and secrete cytokines. E. IgG antibodies produced bind to a specialized Fc receptor called the neonatal Fc receptor (FcRn).

Correct answer: A. As IgG antibody is produced and circulates throughout the body, the antibody binds to antigen that is still available in the blood and tissues, forming immune complexes. B cells specific for the antigen may bind the antigen part of the immune complex by their Ig receptors. At the same time, the Fc tail of the attached IgG antibody may be recognized by a special type of Fc receptor expressed on B cells called FcγRIIB.

Human vision depends on a system of retinal photoreceptor cells, the majority of which are what type of cells and allow you to see in what conditions? a. Rod cells and dim light conditions b. Cone cells and dim light conditions c. Rod cells and the primary colors d. Cone cells and the primary colors e. Rod cells and protanopia

Correct answer: A. The majority of retinal photoreceptor cells, about 95%, are made up of rod cells. The rod cells allow vision in dim light conditions.

A researcher is interested in identifying the quantitative effects of circulating IgG antibodies on immune system regulation. She decides to study the course of a Hepatitis B infection in a mouse over time. Despite an initial surge in IgG levels upon viral exposure, she measures gradually dwindling levels of IgG antibodies following clearance of the infection. Which of the following best explains the cause of this laboratory finding? A. Decreased ITAM activation B. Antibody feedback C. Increased BCR signaling D. Antigen-antibody complexes interact with Ig and Fc receptors of T cells, respectively E. Increased TCR signaling

Correct answer: B. Antibody feedback is the mechanism that serves to terminate humoral immune response once a sufficient quantity of IgG antibodies has been reached. This also limits antibody response against self-antigens and ensures appropriate concentrations of antibodies are in circulation.

A 13-year-old male presents several times to his PCP with symptoms consistent with recurrent intracellular microbial infection. After genetic testing, the patient is found to have a mutation on the X-chromosome, known as X-linked hyper IgM syndrome. This disorder prevents the patient from being able to isotype switch. What function of lymphocyte interaction is most directly affected by this mutation? A. The ability of B cells to express functional CD40 B. The ability of Th cells to express functional CD40L C. A mutation in the activation-induced deaminase enzyme (AID) D. A mutation in the chemokine receptor CXCR5 E. The ability of Th cells to secrete cytokines

Correct answer: B. X-linked hyper IgM syndrome is most directly caused by mutations in the CD40L gene, leading to production of non-functional forms of CD40L on Th cells in males with this genetic disease. CD40L is normally expressed on Th cells and binds to CD40 on B-cells, this interaction, along with cytokine release from Th cells is what signals to B-cells to begin isotype switching. In this disease the major immunoglobulin expressed is IgM, due to loss of isotype switching, leaving the patient susceptible to intracellular microbes

A researcher is studying genetics and encounters the gene called XIST. What is this gene's product? a. factor VIII b. dystrophin c. lncRNA d. factor IX e. vWF

Correct answer: C. The XIST gene is located in the X inactivation center and is required for X inactivation. It encodes a long non-coding RNA (lncRNA) product that coats the inactive X chromosome, which acts as a signal that leads to other aspects of inactivation, including late replication and condensation of the inactive X chromosome. This lncRNA is not translated into a protein.

A 32-year-old female presents to her PCP with a characteristic butterfly rash across her face. Her PCP diagnoses her with a disease in which there is an antibody response against self-antigens. What process normally serves to terminate humoral immune responses once sufficient quantities of IgG antibodies have been produced? A. Affinity maturation B. Isotype switching C. Antibody feedback D. Antigen presentation E. Immune cell activation

Correct answer: C. When sufficient IgG antibodies are produced, a process known as antibody feedback occurs where the Fc tail of the attached IgG antibody is recognized by the Fc(gamma)RIIB receptor. This receptor delivers inhibitory signals that shut down the antigen-receptor induced signals and terminate B cell responses.

A two-year-old male presents to his PCP for persistent cough and low-grade fever. His mother mentions the boy has a history of chronic ear infections and has been diagnosed with streptococcus pneumoniae three times since he was about six months old. Laboratory tests reveal low levels of B-cells and plasma cells. What type of mutation would the boy's physician expect to find through genetic testing? A. SLAM-associated protein (SAM) mutation B. CD-40L mutation C. Mutation of the gamma chain subunit of cytokine receptors D. Bruton tyrosine kinase mutation E. Ataxia telangiectasia mutated (ATM)

Correct answer: D- The boy's symptoms and lab tests indicate X-linked agammaglobulinemia, which is caused by a mutation in a cytoplasmic tyrosine kinase called bruton tyrosine kinase (BTK) that prevents B-cell maturation. Symptoms most often present starting around 6 months old when the mothers antibodies are depleted, and are associated with recurrent bacterial infections of the respiratory tract.

A 3-month-old male presents to his pediatrician's office with his parents. His parents report persistent oral candidiasis for the last month, despite treatment. The patient is at the 3rd percentile for both weight and height. Genetic testing confirms X-linked Severe Combined Immunodeficiency (SCID). In SCID, T-cell numbers are significantly decreased. Which of the following humoral immune responses will be negatively affected by lack of T-cells in SCID? A. IgM B. Low affinity antibodies C. Short-lived plasma cells D. Isotype switching E. Naïve B lymphocytes

Correct answer: D. Antibody responses are classified as either T-dependent or T-independent. This patient has X-linked SCID (as stated above), and in SCID, there is defective IL-17 signaling, which affects early development of lymphocytes, specifically T-cell development. T-cell numbers are significantly decreased in SCID, while B-cell counts are typically normal. Isotype switching is considered a T-cell dependent process, therefore, isotype switching will be negatively affected in SCID.

Fragile X syndrome (FRAXA) is a genetic disease characterized by large ears, long face, hypermobile joints, and intellectual disability. This genetic disease can be seen in both males and females but is more prevalent in males (1 in 4000) than females (1 in 8000). Fragile X syndrome is caused by a mutation in the FMR1 gene, resulting in expanded repeats of a trinucleotide in the 5' untranslated region. Which of the following is the correct number of expanded repeats and trinucleotide that is associated with Fragile X syndrome? A. 6-50 CGG repeats B. 50-200 CGG repeats C. 200-1000 CTG repeats D. 50-200 CTG repeats E.200-1000 CGG repeats

Correct answer: E - Fragile X syndrome is caused by a mutation in the FMR1 gene, resulting in expanded repeats of CGG in the 5' untranslated region. Individuals with Fragile X syndrome have 200-1000 or more CGG repeats which is known as a full mutation.

A little boy presents to his pediatrician for his 3-year check up, and upon physical exam he is observed to have hypermobile joints, large ears, and a long face. Additionally, he appears to be developmentally delayed and does not exhibit normal behavior for a toddler of his age. The pediatrician orders genetic testing for suspicion of an underlying genetic abnormality. The child's parents lack any of these features described in their son, and are confused about how he must have inherited this condition. Which of the following is the correct explanation for the inheritance of this disorder, so these parents can understand how their child has been affected? a. Fragile X is an x-linked disorder that can be inherited through the father or mother. b. Fragile X is an x-linked disorder most commonly inherited through the father. c. Fragile X manifestation exhibits the concept of anticipation, where expansion of DNA repeats increases with each generation, leading to more severe disease with each generation. d. Both A and C e. Fragile X manifestation exhibits the concept of anticipation, where expansion of DNA repeats decreases with each generation, leading to more severe disease with each generation.

Correct, choices A and C. Fragile X manifests itself more severely with each generation due to the concept of anticipation, where DNA repeats expand with each generation. Mothers carry a permutation of 50-200 CGG repeats, resulting in offspring that may inherit additional CGG repeats (the full mutation is defined by more than 200 repeats). This explains why mom and dad are asymptomatic, but have a child with the syndrome (mom has premutation because her son is affected -

A concerned mother brings her 1 year old son into the pediatrician. She states the child has been having recurrent infections and has a rash that will not go away after she tried different creams for it. The physician recognized the rash as eczema and ordered blood work to further investigate. The lab results showed that he had low platelet levels, his IgG levels were normal, his IgM levels were a little low, and he had elevated IgA & IgE levels. Suspecting an X-linked disease, she orders a genetic test looking for which gene mutation? A. A V(D)J recombination mutation B. Inherited mutation in Th17 responses C. Deleted region in TBX1 gene D. Wiskott-Aldrich syndrome protein (WASP) mutation E. Bruton tyrosine kinase (BTK) mutation

D - Correct: patients with a X-linked WASP mutation experience thrombocytopenia, eczema, and a marked vulnerability to recurrent infections, which is characteristic for Wiskott-Aldrich Syndrome. WASP proteins are believed to link membrane receptors, but the function of the protein is unclear.

A 15 year old male visits his PCP complaining about excessive thirst (polydipsia) and urine production (polyuria). He also experiences nocturia, unexplained fevers, lethargy, and irritability. He is diagnosed with an X-Linked Recessive Disorder. What is the diagnosis? A. Juvenile retinoschisis B. Leri-Weill dyschondrosis C. Vitamin D-resistant rickets D. Nephrogenic diabetes insipidus E. Pelizaeus-Merzbacher disease

D. Correct - Nephrogenic diabetes insipidus is associated with AVPR2 gene and is characterized by impaired response to antidiuretic hormone that leads to inability to concentrate urine, polydipsia (excessive thirst), and polyuria (excessive urine production)

A patient's blood test reveals normal levels of B and T cells but extremely low levels of Ig"X" as well as the absence of certain other antibodies. His physician carefully explains to him that he has a genetic disorder that is caused by mutations in the gene encoding CD40L which interfere with CD4+ helper T cell function, and that the genetic disorder follows the X-linked pattern of inheritance. Which of the following antibody levels in the patient are correctly matched with this disorder? A. IgA - elevated B. IgE - extremely low C. IgM - extremely low D. IgG - normal E. IgM - elevated

E. Correct. This genetic disorder is Hyper-IgM syndrome. The serum of persons with this syndrome contains normal or elevated levels of IgM but no IgA or IgE and extremely low levels of IgG (referred to as Ig"X" in question stem). *** Either normal or elevated levels of IgM are present in this disorder; among these answer choices, elevated IgM levels is the best choice

A 30 year old female goes into labour and is rushed to the ER. After giving birth to a boy, the OB-GYN notices that the child is quite large for his age, has a large tongue, creases on his earlobe as well as an odd looking abdomen. The child also appears hypoglycemic. What is the most likely diagnosis ? A ) Prader- Willi syndrome B ) Beckwith-Wiedmann syndrome C ) Angelman syndrome D ) Silver-Russell syndrome E ) LHON

Explanation : B ) The child presents with recognisable traits for Beckwith-Wiedmann syndrome. Hypoglycemia, abdominal wall defect [omphalocele], large tongue, creases on the ear lobe, and finally being a very large size for gestational age. It is the ONLY syndrome out of the others that presents as an OVERGROWTH rather than undergrowth (due to increased IGF2 levels)

A physician is researching the immune system, specifically the interaction between B cells and T cells. Which of the following is true about the cross presentation of antigens by B lymphocytes to helper T cells? A. T cells recognize one epitope of the antigen but display different epitopes for recognition. B. A hapten can only stimulate an immune response when attached to a carrier protein. C. B lymphocytes endocytose antigens, process them and display class I MHC peptides for recognition by CD4 T cells. D. B lymphocytes bind an epitope of a native protein antigen, internalize and process the antigen and display a single peptide from that protein for T cell recognition. E. Polysaccharides stimulate strong immune responses in infants and children.

The correct answer choice is B: The answer choice describes a hapten. A hapten can only provide an effective immune response whend it is conjugated to a carrier protein.

A 17-year-old male student, who is an aspiring pre-med student, presents to his primary care physicians for his yearly physical. He tells his physician that he feels run down and worried about being sick. He states he was learning about his immune system and how it fights infections. The physician starts to describe how antigens will bind to the B-cell. Which of the following will be phosphorylated when two or more antigen receptors of a B-cell are brought together by antigen-induced crosslinking? A. B-cell Receptors (BCR) B. T-cell Receptors (TCR) C. Immunireceptor tyrosine-based activation motif (ITAM) D. Macrophages E. Helper T-cells

The correct answer is C because ITAM is located within 2 proteins (Igα and Igβ) that are noncovalently attached to the Ig-molecules. ITAM and Ig-molecules make up the B-cell receptors. When two or more antigen receptors of a B cell are brought together by antigen-induced cross-linking, the tyrosines in the ITAMs of Igα and Igβ are phosphorylated by tyrosine kinases associated with the BCR complex.

A 29-year-old female presents to her Primary Care Physician for her routine physical. Upon inquiring about COVID-19 and the recent announcement that each person is now eligible for vaccination, they begin chatting about the different subsets of the immune system. The patient is curious about which types of cells are largely responsible for the response to blood-borne polysaccharide and lipid antigens. The physician explains that those cells are in the peripheral splenic white pulp and outer rim of lymph node follicles. Which of the following subset of cells is the physician specifically referring to? A. Helper T Cells B. Marginal-zone B Cells C. Plasma cells D. B-1 Cells E. Macrophages

The correct answer is Choice B: Marginal-zone B cells. Marginal-zone B cells are the subset of B cells that respond largely to blood-borne polysaccharide and lipid antigens. Marginal-zone B cells make predominantly T-independent IgM antibodies as a response to these pathogens, and reside in the peripheral region of the splenic white pulp

A 37 year old female presents to her physician with complaints of body aches, fever, and increased fatigue. She states that she has not done anything out of the ordinary lately but she did recently attend a family cookout where pork chops were served. The physician runs a blood test and diagnoses the patient with a parasitic toxoplasmosis infection. She is prescribed a combination of sulfadiazine and a folate analog to treat the infection. What is the specific folate analog that she was prescribed? a. Methotrexate b. Pyrimethamine c. Trimethoprim d. Amoxicillin e. Dapsone

b. Correct: Pyrimethamine is a folate analog that selectively inhibits parasitic DHFR. It is the only effective chemotherapeutic agent against toxoplasmosis and it is frequently used in combination with sulfadiazine.