Ch. 4 Success Immunology and Serology (100 q.)

84. Rheumatic fever sometimes occurs after group A streptococcal infections. In this condition, an auto immune response attacks the tissue of the heart valves. This phenomenon is an example of: A. Epitope spreading B. Molecular mimicry C. Polyclonal B cell activation d. Preferential activation of T helper cells

B. Molecular mimicry Group A streptococci contain antigenic determinants that are similar to antigenic determinants found on heart valve tissues in some individuals. The immune response occurring during the course of a group A streptococcal infection may be extensive enough to include an immune mediated attach on the heart valves - rheumatic heart disease. "Molecular mimicry" is the term given to this phenomenon, whereby an immune response directed against one antigen may be extended to include activity against closely related antigens.

85. "Superantigens" are toxins produced by some strains of Staphylococcus aureus and group A streptococci and cause damage by: A. Molecular mimicry B. Polyclonal T cell activation C. Lysing white blood cells and platelets D. Lysing red blood cells

B. Polyclonal T cell activation Some strains of Staphylococcus aureus and group A streptococci produce toxins that have the properties of "superantigens." Superantigens react with T cells directly without processing by an antigen presenting cell. These toxins can stimulate many T cells, rather than only those T cells bearing T cell receptors specific for the bacterial toxins. The result is a massive T cell response, leading to the release of cytokines and resulting in disease entities known as toxic shock syndrome (in the case of S. aureus infection) and toxic shock like syndrome in the case of group A streptococci.

60. Skin testing is a useful diagnostic tool in a number of disorders, such as tuberculosis. Which of the following statements about skin testing is true? A. A positive test depends on preformed antibody. B. Reactivity to a particular antigen may be transferred from one individual to another by sensitized lymphocytes C. The intensity of the response correlates directly with the clinical activity of the disease D. The maximum response will occur immediately

B. Reactivity to a particular antigen may be transferred from one individual to another by sensitized lymphocytes Skin testing is based upon the presence of T cells sensitized to antigen. Their activation produces a delayed hypersensitivity reaction, which reaches its peak in about 48 hours. There is no correlation of the amount of the reaction with clinical disease. If the sensitized T cells are transferred from one individual to another, the recipient individual will manifest the same delayed hypersensitivity as the donor.

82. Patient serum is mixed with a suspension of guinea pig antigen. When the sample is then mixed with horse red blood cells, agglutination occurs. This is suggestive of an infection caused by: A. Borrelia burgdorferi B. Hepatitis B virus C. Hepatitis C virus D. Epstein-Barr virus

D. Epstein-Barr virus The Davidsohn differential test can be used to detect heterophile antibodies produced during infectious mononucleosis. These antibodies are not adsorbed by guinea pig antigens. Therefore, the antibodies are available to agglutinate horse red blood cells. Forssman heterophile antibodies are absorbed by guinea pig antigens and would not agglutinate the horse red blood cells.

77. Which of the following is an example of a treponemal antigen test used for the diagnosis of syphilis? A. CRP B. RPR C. VDRL D. FTA-ABS

D. FTA-ABS The fluorescent treponemal antibody absorbance (FTA-ABS) test is often used as a confirmatory test for syphilis. Treponema pallidum subsp. pallidum, the causative agent of syphilis, is the source of the antigen. The rapid plasma reagin (RPR) and Venereal Disease Research Laboratory (VDRL) are diagnostic tests for syphilis that use nontreponemal antigen. CRP is not involved in syphilis testing.

86. The first serologic marker to appear in patients with acute hepatitis B virus infection is: A. Anti-HB B. Anti-HBc C. Anti-HBe D. HBsAg

D. HBsAg HBsAg is the first serologic marker occurring in patients with hepatitis B virus infection. The antigen appears about 3-5 weeks before symptoms appear. About 2-4 weeks later, anti-HBc, primarily of the IgM class, beings to appear.

90. Why does vaccination against hepatitis B virus (HBV) also prevent hepatitis D virus (HDV) infections? A. An immunogen from HBV in the vaccine is also associated iwth HDV. B. The HBV vaccine induces formation of heterophile antibodies that cross react with HDV C. The HBV vaccine stimulates liver cells to produce antiviral molecules active against all hepatitis viruses D. HDV requires the host to be concurrently infected with HBV

D. HDV requires the host to be concurrently infected with HBV HDV requires HBsAg produced by HBV infected cells. HDV, therefore, requires the host to be concurrently infected with HBV. The HBV vaccine prevents HBV infection and also HDV infection.

58. Monoclonal antibodies are produced by: A. Cultured T cells B. Human plasma Cells C. Mouse plasma cells D. Hybridomas

D. Hybridomas A monoclonal antibody is produced by a single cell or clone. Plasma cells obtained from an immunized animal and subsequently fused with myeloma cells results in hybrid myeloma or hybridoma that will indefinitely secrete a specific antibody. Hybridomas have been prepared from mouse and human plasma cells fused with myeloma cells. T cells do not produce antibodies.

22. The serologically detectable antibody produced in rheumatoid arthritis (RA) is primarily of the class: A. IgA B. IgE C. IgG D. IgM

D. IgM Rheumatoid Factor (RF) is an immunoglobulin that reacts with antigenic determinants on an IgG molecule. Although they may be of several types, the one that is easily serologically detectable is IgM. This is because of the agglutination activity of the molecule. RF tests are commonly used in the diagnosis of rheumatoid arthritis.

15. Which class of immunoglobulin possesses 10 antigenic binding sies? A. IgA B. IgD C. IgG D. IgM

D. IgM The IgM molecule is a pentamer that contains 10 binding sites. Howevver, the actual valence falls to 5 with larger antigen molecules, probably because of steric restrictions. IgA, IgG, IgD, and IgE monomers each have two antigenic bindings sites.

27. After exposure to antigen, the first antibodies that can be detected belong to the class: A. IgA B. IgE C. IgG D. IgM

D. IgM The first B cells to respond to antigen differentiate into plasma cells that produce IgM antibody. Later in the immune response, stimulated B cells ndergo a phenomenon called "class switching" and begin to produce antibodies of the IgG, IgA, and IgE classes. High concentrations of IgM in patient serum is indicative a recent infection.

57. Which of the following statements applies to the Fc fragment of an immunoglobulin molecule? A. It consists of the entire heavy chain B. It contains the variable region of the heavy chain C. It contains the antigen binding sites of the molecule D. It is the region of the molecule that binds to receptors on various white blood cells

D. It is the region of the molecule that binds to receptors on various white blood cells The Fc (crystalline) fragment of an immunoglobulin is produced by papain digestion of an immunoglobulin monomer. The Fc portion of antibodies binds to specific Fc receptors on the surface of some white blood cells. Only part of the heavy chain is found in the Fc fragment. The Fab fragment contains the antigen combining sites of both the heavy and light chains.

11. What is the predominant type of antibody found in the serum of neonates born after full-term gestation? A. Infant IgA B. Infant IgG C. Infant IgM D. Maternal IgG

D. Maternal IgG Antibody production is immunogen induced. Because the fetus develops in a sequestered site, it makes very little immunoglobulin. Maternal IgG crosses the placenta and is the primary antibody found in infant's circulation.

48. Identical antibodies produced from a single clone of plasma cells describes: A. Reagin B. Cold agglutinins C. Heterophile antibodies D. Monoclonal antibodies

D. Monoclonal antibodies Monoclonal antibodies are derived from a single clone of plasma cells. Plasma cells are fused with a cancerous myeloma cell. Reagin has two meanings: it can refer to the antibody produced during syphilis or it can refer to IgE. Cold agglutinins are antibodies that agglutinate in cold temperatures. Heterophile antibodies are antibodies produced following exposure to an immunogen that are able to bind a similar but different molecule.

41. Innate immunity inclues: A. Anamnestic response B. Antibody production C. Cytotoxic T cell activity D. Phagocytosis by polymorphonuclear cells

D. Phagocytosis by polymorphonuclear cells Innate, or nonspecific, immunity refers to host defenses that are in general present at birth and do not require immunogen stimulation. Phagocytosis of bacteria by polymorphonuclear cells in an example. Cytotoxic T cell activity is part of the adaptive cell mediated immune response, and antibody production is the mechanism of protein in the adaptive humoral mediated immune response.

76. A soluble antigen and soluble antibody reacting to form an insoluble product describes: A. Agglutination reactions B. Heterophile reactions C. Labeled reactions D. Precipitation reactions

D. Precipitation reactions Precipitation reactions involve both soluble antigens and antibodies. These reactions are typically detected in agarose gels. With agglutination reactions, one of the reactants is soluble and the other is insoluble. A reactant is made insoluble by combining with a carrier particle such as latex beads.

46. One cause of a false-positive VDRL test is: A. Brucellosis B. Treponema pallidum infection C. Rocky mountain spotted fever D. Systemic lupus erythematosus

D. Systemic lupus erythematosus Patients with connective tissue disorders such as systemic lupus erythematosus may show a false positive reaction in the VDRL test. Other causes of false positives include rheumatic fever, infectious mononucleosis, malaria, and pregnancy. Treponema palldium subsp. pallidium is the causative agent of syphilis.

30. In Bruton disease, measurement of serum immunoglobulins would show: A. Elevated levels of IgE B. Elevated levels of IgG C. Normal levels of IgG and IgM but reduced levels of IgA D. The absence of all immunoglobulins

D. The absence of all immunoglobulins Bruton disease is a congenital form of agammaglobulinemia. It is a sex linked phenomenon that affects males. Because B cells are not produced, affected males have levels of IgA, IgD, IgE, and IgM undetectable by routine assays. IgG may be absent or present at very low levels.

28. Corneal tissue may be transplanted successfully from one patient to anotehr becuase: A. The cornea is nonantigenic B. Corneal antigens do not activate T cells C. Anticorneal antibodies are easily suppressed D. The cornea occupies a privileged site not usually seen by the immune system

D. The cornea occupies a privileged site not usually seen by the immune system Corneas are readily transplanted from one individual to another. This is because the cornea is nonvascularlized and is a sequestered site. Thus the immune system of the host does not "see" the cornea and recognize it as foreign.

83. Hashimoto disease is an autoimmune disease primarily involving the: A. Kidneys B. Liver C. Lungs D. Thyroid gland

D. Thyroid gland Hashimoto disease is a type of thyroiditis due to an autoimmune disease. Patients produce autoantibodies and T cells that respond to thyroid antigens. This results in inflammation and swelling of the thyroid gland (goiter). The autoantibody blocks the uptake of iodine, which results in a decrease in the production of thyroid hormones (hypothyroidism).

66. An autoimmune disease causing destruction of pancreatic cells can result in: A. Hashimoto disease B. Multiple sclerosis C. Myasthemia gravis D. Type I diabetes

D. Type I diabetes Destruction of the beta cells in the pancreas results in type I diabetes. An autoimmune response destroys the insulin producing cells. The immune response is probably due to molecular mimicry. Cytotoxic T cells and antibodies directed against an infectious agent cross react to the beta cells.

70. Which of the following is characteristic of contact hypersensitivity reactions? A. Caused by preformed IgE antibody B. Characterized by infiltration of neutrophils into the area of reaction C. The primary symptoms often occur in the respiratory tract. D. Usually due to a hapten

D. Usually due to a hapten Contact dermatitis is a cell mediated hypersensitivity reaction. The offending substance is typically a hapten that combines with a carrier molecule on the skin surface. The hapten carrier complex is recognized by T cells. IgE mediates immediate hypersensitivity reactions such as hay fever and some forms of asthma.

98. A male infant had been well until about 5 months of age, at which time he was diagnosed as having otitis media and bronchitis caused by Haemophilus influenzae. Over the next serval months he presented with stroptococcal pneumonia several times. At 10 months of age a serum protein electrophoresis showed a virtual lack of gamma globulins. Quantitative serum levels were as follows: 75 mg/dL IgG and undetectable levels of IgM, IgA and IgE. there were a normal number of T cells, and they exhibited normal mitogen stimulation. What disease does this child most likely suffer from? A. Combined immunodeficiency B. DiGeorge syndrome C. Iatrogenic immunodeficiency D. X-linked agammaglobulinemia

D. X-linked agammaglobulinemia The case history is typical of a child with X linked agammaglobulinemia. He presented with chronic and recurrent infections beginning at 5 months of age, when transplacentally acquired IgG had declined. Normal IgG serum level is about 800-1200 mg/dL. The infant had normal T cell function, which rules out combined immunodeficiency and DiGeorge syndrome. "Iatrogenic immunodeficiency" refers to an immunodeficiency following therapy prescribed by a physician.

67. An Ouchterlong gel diffusion plate is depicted in Color Plate 24. The center well contains antibody and the peripheral wells contain antigens labeled 1 through 4. What is the relationship between the antigens in wells 2 and 3? A. 2 is part of 3. B. 3 is part of 2. C. they are identical D. they are unrelated

D. they are unrelated The two antigens are not related. There are two different antibodies that are able to react with the two antigens, forming precipitin lines that cross. If the antigens were identical, a smooth curve precipitation line would have formed.

99. A 25- year old male presents to his family physician complaining of fatigue, diarrhea, and wight loss of a few months duration. On physical examination the patient is found to have a fever and abdominal discomfort. Laboratory results indicate a white blood cell count of 14.3x 10^9/L (reference range 4.8-10.8 x10^9/L). Assays for HBSAg and anti-HCV are negative. An ELISA test for antibodies to the human immunodeficiency virus (HIV) performed on the patient's serum is found to be reactive. What step should be taken next? A. Call the physician with the HIV result B. Repeat the HIV ELISA test on the sample C. Test the patient's serum for anti-HBS D. Contact the patient to collect a second sample.

B. Repeat the HIV ELISA test on the sample When a standard screening test for human immunodeficiency virus infection, such as an ELISA, is positive, it is recommended that the sample be repeated in duplicate. If one or both of the repeated tests is reactive, the sample is considered to be repeatedly reactive and needs to be confirmed by a confirmatory test (e.g., Western blot of immunofluorescent antibody). If this test is positive, the sample can be reported as positive. If the confirmatory test is negative, an additional confirmatory test should be performed if the patient has risk factors for HIV infection. If the repeated ELISA tests are both negative, the sample is reported as negative.

33. Which cell is the principal source of interleukin 2? A. B cell B. T cell C. Monocytes D. Plasma cell

B. T cell IL-2 is a lymphokine produced by activated T helper cells. IL-2 principally affects T cells, including the cell that released IL-2, acting on its target cells via the IL-2 receptor. This receptor is not represent on resting cells.

6. Cell-mediated immunity is primarily mediated by: A. B cells B. T helper cells C. Plasma Cells D. Dendritic cells

B. T helper cells T helper cells are the primary mediators of cell mediated immunity (CMI). They secrete several different lymphokines that stimulate a number of other cells, such as cytotoxic T cells and monocytes. B cells differentiate into plasma cells during a humoral mediated immune response. Dendritic cells are important antigen presenting cells, but they are not the primary mediators of a CMI response.

92. Contact dermatitis is mediated by: A. B lymphocytes B. T lymphocytes C. Macrophages D. Polymorphonuclear cells

B. T lymphocytes Contact dermatitis is a delayed type hypersensitivity reaction mediated by T cells. Antibody is not involved in this type of hypersensitivity, so B cells play no role in it. Neither macrophages nor neutrophils are involved in this type of hypersensitivity.

56. Which of the following statements about immunoglobulin light chains is true? A. Each immunoglobulin monomer has either one kappa or one lambda chain B. There are two types: kappa and lambda C. They consist of constant regions only D. They form part of the Fc fragment

B. There are two types: kappa and lambda Light chains are of two distinct types: kappa and lambda. Either type may combine with any of the heavy chains, but in any one molecule, only one type is found. Each immunoglobulin monomer contains two light chains, either kappa or lambda. They extend into the Fab, or antigen binding, site. This half of the chain is highly variable, whereas the carboxy terminal portion of the molecule is a constant region.

68. An Ouchterlong gel diffusion plate is depicted in Color Plate 24. The center well contains antibody, and the peripheral wells contain antigens labeled 1 through 4. What is the relationship between the antigens in wells 2 and 4? A. Cannot be determined B. They are identical C. They are unrelated D. They react incompletely with the antibody

B. They are identical When two antigens are identical, a smooth curved line of precipitation is formed between them. In the diagram, the antigen in well 2 is identical to one of two antigens in well 1. The same antigen in well 1 is identical to antigen in well 4. Therefore, if follows that antigens 2 and 4 are identical.

75. Incompatible blood transufsions are examples of: A. Type I hypersensitivity reactions B. Type II hypersensitivity reactions C. Type III hypersensitivity reactions D. Type IV hypersensitivity reactions

B. Type II hypersensitivity reactions Incompatible blood transfusions are examples of a type II hypersensitivity reaction. These reactions are characterized as the antigen being a part of a cell. Antibody binds to the antigen, complement is activated, and the red blood cells are lysed.

94. An antibody titration is depicted in COlor Plate 25. In this tiration , a 0.2 mL aliquot of patient's serum sample was addded to 0.8 mL of saline, and this mixture was placed into tube #1. A 0.5 mL sample was removed from tube #1 and placed into tube #2, containing 0.5 mL of saline. This procedure was repeated through tube #10. The dilutions were assayed for antibody to an infectious agent. How should the antibody titer be reported? A. 256 B. 512 C. 640 D. 1280

C. 640 The titer of this assay is the reciprocal of the highest dilution demonstrating the desired result, in this case tube #8. The dilution is determined as shown below: Dilution for tube #1: 0.2 mL serum in a total volume of 1 mL = 1:5 dilution Dilutions in succeeding tubes: 0.5 mL diluted serum in a total volume of 1 mL = 1:2 dilution The dilutions in the series of tubes are as follows: Tube #1, 1:5; tube #2, 1:10; tube #3, 1:20; tube #4, 1:40; tube #5, 1:80; tube #6, 1:160; tube #7, 1:320; tube #8, 1:640; tube #9, 1:1280; tube #10, 1:2560 T he reciprocal of the dilution in tube #8 is 640.

40. The type of immunity that follows the injection of antibodies synthesized by another individual or animal is termed: A. Artificial active B. Natural adaptive C. Artificial passive D. Natural passive

C. Artificial passive Artificial passive immunity results following the injection of antibody synthesized by another individual or animal. This type of immunity is only temporary but may be very important in providing "instant" protection from an infectious agent before the recipient would have time to actively synthesize antibody. The injected antibodies are treated as foreign proteins and are eventually cleared from the body.

88. Cells that can act as antigen-presenting cells for exogenous antigens include A. All nucleated cells B. Endothelial cells C. B Lymphocytes D. T Lymphocytes

C. B Lymphocytes Exogenous antigens are nonself antigens derived from infectious agents or immunizing preparations. Exogenous antigens are processed for presentation to specific T cells by specialized cells collectively referred to as antigen presenting cells (APCs). APCs for exogenous antigens include B cells, macrophages, monocytes, and dendritic cells.

65. Which complement protein is present in the greatest concentration in human serum? A. C1 B. C2 C. C3 D. C4

C. C3 Complement protein C3 has a serum concentration of about 1300 ug/mL, which makes it the complement protein present in the greatest concentration. The second highest concentration of complement protein is C4 (600 ug/mL). C3 is cleaved into fragments: C3a and C3b.

96. A 28 year old female complains to her family physician of abdominal pain, loss of appetite, and low-grade fever. Physical examination reveals abdominal tenderness and a low-grade fever. Her physician orders a hepatitis profile and obtains the results below: Anti-HAV- nonreactive Anti-HBc- Reactive Anti-HBs- Nonreactive HBsAg- Reactive HBeAg- Reactive Anti-HCV- Nonreactive Which of the following is the most likely conclusion? A. Acute HAV infection B. Acute HBV infection C. Chronic HBV infection D. Immunity to HBV due to past infection

C. Chronic HBV infection The presence of HBsAg indicates viral replication and that the patient is infectious; this marker can be seen in both acute and chronic infections. The lack of anti-HBs indicates that the patient is not immune to the infection. The presence of anti-HBc and HBeAg with HBsAg indicates a chronic infection.

19. When performing the enzyme-muliplied immunoassay technique (EMIT), how is the ligand in the patient's serum detected? A. Agglutinates by binding to antiboyd-coated latex beads B. Binds to enzyme-labeled antibody C. Competes with enzyme-labeled antigen for binding to a specific antibody D. Forms antibody-antigen complex and precipitates

C. Competes with enzyme-labeled antigen for binding to a specific antibody In the EMIT, a ligand (antigen) in a sample competes with an enzyme labeled ligand for binding to a specific antibody. The labeled ligand is designed so that following antibody binding, the enzyme is inactive. As the ligand concentration in the test sample increases, more enzyme labeled ligand ligand remains unbound, resulting in greater enzyme activity.

12. An improtant part of the nonspecific immune response is (are): A. B cells B. Basophils C. Complement cascade D. Cytotoxic T lymphocytes

C. Complement cascade Important parts of an animal's nonspecific immune response include phagocytosis, inflammation, and complement activation. In a nonspecific immune response, the animal responds in much the same way to all invaders. B cells and cytotoxic T lymphs responded to specific antigens and are, therefore, involved in the specific immune response. Basophils are involved in type I hypersensitivity reactions.

44. The rapid plasma reagin assay for syphilis does not need to be read microscopically because the antigen is: A. Cardiolipin B. Complexed with latex C. Complexed with charcoal D. Inactivated bacterial cells

C. Complexed with charcoal The rapid plasma reagin (RPR) and Venereal Disease Research Laboratory (VDRL) tests use a cardiolipin antigen. However, in the RPR test, charcoal particles are included with the antigen. When antibody in the patient sample combines with the antigen, the charcoal is trapped in the immune complex, allowing the reaction to be read macroscopically.

3. Which of the following is characterstic of B cells? A. Phagocytic B. Participate in antibody-dependent cellular cytotoxicity (ADCC) reactions C. Contain surface immunolobulins D. Secrete the C5 component of complement

C. Contain surface immunolobulins B cells carry surface immunoglobulins that react to a specific antigen. The antigen can then be internalized processed and presented to an appropriate T helper cell. B cells are not phagocytic, nor do they participate in antibody-dependent cellular cytotoxicity (ADCC) reactions. Complement proteins are secreted by hepatocytes.

47. The portion of an antigen that binds to an antibody or T cell receptor is called a(n): A. Allergin B. Avidin C. Epitope D. Valence

C. Epitope Antigens can have multiple epitopes. Each epitope can be unique, binding an antibody with a different idiotype. "Valence" refers to the number of epitopes on an antigen.

62. Interaction between B and T helper cells involves A. MHC II molecule on B cell binding to MHC I molecule on the T cell B. MHC II molecule on B cell binding to CD3 on the T cell C. Foreign antigen on B cell binding to T cell receptor D. CD3 molecule on B cell binding to T cell receptor

C. Foreign antigen on B cell binding to T cell receptor B cells have the ability to present antigen (immunogen) to T helper cells. This interaction involves several surface molecules. The antigen is complexed with MHC II on the surface of the B cell. CD4 on the T cell interacts with MHC I, whereas the T cell receptor binds the antigen.

23. In bone marrow transplantation, immunocompetent cells in the donor marrow may recognize antigens in the recipient and respond to those antigens. This phenomenon is an example of: A. Acute rejection B. Chronic rejecton C. Graft versus host disease D. Hyperacute rejection

C. Graft versus host disease Bone marrow transplants by their nature contain immunologically competent cells: B cells and T cells in particular. Unless the transplanted marrow is HLA matched perfectly to the donor, the immunocompetent cells in the transplant will recognize and react against the nonself HLAs of the recipient's tissues. This phenomenon is known as GVHD, because the graft attempts to reject the host. Acute rejection, chronic rejection, and hyperacute rejection are examples of mechanisms a recipient's immune system uses to reject a graft.

59. Antibodies that bind to the same epitope are of the same: A. Allotype B. Autotype C. Idiotype D. Isotype

C. Idiotype Idiotype of an antibody refers to the antigen specificity of the molecule. The isotype is the different classes and subclasses of antibodies (e.g. IgG, IgM, etc.), "Allotype" refers to different alleles of the same isotype. Genetically different individuals will produce antibodies of the same isotype, but they would have a different allotype.

17. Which class of immunoglobulin binds to basophils ad mast cells to mediate immediate hypersensitivity reactions? A. IgA B. IgD C. IgE D. IgG

C. IgE Mast cells and basophils have surface receptors for the Fc portion of IgE. When IgE molecules, attached to the surface of mast cells and basophils, bind the allergen they are specific for, this triggers the cells to degranulate, producing the symptoms of immediate type I hypersensitivity. The main function of IgE appears to be the ability to trigger an immune response, thereby recruiting plasma factors and effector cells to areas of trauma or parasite infection.

13. The major class of immunoglobulin found in adult human serum is: A. IgA B. IgE C. IgG D. IgM

C. IgG Immunoglobulin G is the predominant class of immunoglobulin found in serum. It accounts for approximately 80% of the total serum immunoglobulin. The normal range is 800-1600 mg/dL.

34. Diagnostic reagents useful for detecting antigen by the coagglutination reaction may be prepared by binding antibody to killed staphylococcal cells via the Fc receptor of staphylococcal protein A. The class of antibody bound by this protein is: A. IgA B. IgD C. IgG D. IgM

C. IgG Staphylococcal protein A binds only the IgG class (subclasses IgG1, IgG2, and IgG4) of immunoglobulin. Binding occurs via the Fc portion of the antibody molecule. Leaving the Fab portion available to bind antigen in an immunologic assay. Binding of the Fab portion to test antigen causes agglutination of the staphylococcal cells (coagglutination).

20. Severe combined immunodeficiency (CID) is an: A. Immunodeficiency with decreased B cells and neutrophils B. Immunodeficiency with lymphocytopenia and eosinophilia C. Immunodeficiency with decreased or dysfunctional T and B cells D. Immunodeficiency with decreased lymphocytes and decreased complement concentration

C. Immunodeficiency with decreased or dysfunctional T and B cells SCID is defined as a condition in which adaptive immune responses (i.e., cell mediated and humoral mediated immune responses) do not occur because of a lack of T and B cell activity. A number of genetic defects can lead to this condition. Children born with SCID need to live in a sterile environment, and they have a short life expectancy.

29. A kidney transplant from one identical twin to another is an example of a(n): A. Allograft B. Autograft C. Isograft D. Xenograft

C. Isograft Identical twins have the same genetic makeup. Grafts between them would be isografts or syngeneic grafts. Autografts are transplantations from one site to another in the same individual Xenograft refers to transplantation between different species. Transplantation between two nonidentical individuals of the same species is called an allograft.

81. A patient report states the presence of serum antibodies to OspC. What disease does the patient most likely have? A. Syphilis B. Strep throat C. Lyme disease D. Rubella

C. Lyme disease IgM antibody to OspC is an important early marker in the diagnosis of Lyme disease. This antibody, along with several others, is often detected by Western blot. Antibodies to p35, p39, and the flagellin subunits p37 and p41 are also useful in diagnosing this disease.

74. A cut on a person's finger becomes contaiminated with the bacterium Stephyloccus aureus. The first response by the immune system consists of activity of: A. B cells B. Monocytes C. Neutrophils D. T cells

C. Neutrophils The first response to invading bacteria is mounted by the innate immune system. The innate immune system, although it lacks the specificity of the adaptive immune system, is nonetheless effective at handling many invading bacteria. The first response by the innate immune system consists of an influx of neutrophils into the tissue invaded by bacteria. Monocytes and macrophages, although they are phagocytic cells and part of the innate immune system, play only a minor role in the initial response to bacterial invasion.

43. The antibody most frequently present in systemic lupus erythematosus is directed against: A. Surface antigens of bone marrow stem cells B. Surface antigens of renal cells C. Nuclear antigen D. Myelin

C. Nuclear antigen Antinuclear antibody (ANA) is the most consistent feature of systemic lupus erythematosus (SLE). Although renal or nerve pathology amy occur, that pathology is secondary to deposition of antigen antibody complexes and subsequent activation of complement proteins. Bone marrow stems cells are not involved in the pathology of SLE.

10. A young woman shows increased susceptibility to pyogenic infection. Upon assay, she show a low level of C3. Which of the following statements is probably true? A. She has an autoimmune disease with continual antigen-antibody activity causing consumption of C3 B. She has DiGeorge syndrome C. She has decreased production of C3 D. She may produce an inactive form of C2, a precursor of C3.

C. She has decreased production of C3 C3 may be decreased due to a genetic defect that causes deficient production. In certain autoimmune disorders, such as systemic lupus erythematosus, continual complement activation leads to low levels; however, susceptibility to pyogenic infections is not a feature of autoimmune diseases. DiGeorge syndrome is a deficiency in T cells, and complement protein C2 is not a precursor of C3.

37. How does the secondary humoral immune response differ from the primary response? A. The lag phase (the time between exposure to immunogen and production of antibody) is longer in the secondary immune response B. IgM is the predominant antibody class produced in the secondary immune response. C. The antibody levels produced are higher in the secondary immune response. D. Cytotoxic T lymphocytes play an important role in the secondary response.

C. The antibody levels produced are higher in the secondary immune response. The secondary immune response is characterized by the predominance of IgG over IgM. In addition, because of the formation of memory cells following the primary response, the secondary response occurs much more quickly and strongly. This is the basis for immunization as a protection against various infectious diseases. Cytotoxic T lymphs are not involved in humoral immunity.

2. A hapten is: A. Half of an immunoglobulin molecule B. A carrier molecule for an antigen that is not antigenic alone C. An immunoglobulin functional only in the presence of complement D. A determinant capable of stimulating an immune resonse only when bound to a carrier

D. A determinant capable of stimulating an immune resonse only when bound to a carrier Haptens are substances that are not immunogenic by themselves. These molecules are not large or complex enough to stimulate the immune system. When bound to a carrier, they are capable of stimulating a specific immune response.

87. A living donor is being sought for a child who requires a kidney transplant. The best odds of finding an MHC-compatible donor occur between the child and: A. A sibling (brother or sister) B. An unrelated individual C. The Child's father D. The child's mother

A. A sibling (brother or sister) Because the human leukocyte antigen (HLA) system is extremely polymorphic, the odds are greatly against finding an HLA compatible donor in unrelated individuals. The genes coding for HLA antigens are inherited form one's parents and are expressed codominantly. Between an offspring and either parent, there is, statistically, a 25% chance of an HLA match. Between siblings, there is a 50% chance of an HLA match.

9. Which of the following is more likely to be diagnostic of an acute infection? A. A total acute antibody titer of 2 followed by a convalescent titer of 16 B. A total acute antibody titer of 80 C. A total antibody titer of 80 D. An IgG antibody titer of 80

A. A total acute antibody titer of 2 followed by a convalescent titer of 16 The most significant indicator of acute or recent infection is the presence of a rising antibody titer. A fourfold or greater rise in titer, from 2 to 16, is significant. Even relatively high antibody titers of IgG may indicate past infections. IgM is produced first following infections, so a high IgM titer is also suggestive of an acute infection.

21. An example of immune injury due to the deposition of antigen-antibody complexes is: A. Acute glomerulonephritis B. Bee-sting allergy C. Contact dermatitis D. Penicillin allergy

A. Acute glomerulonephritis Acute glomerulonephritis is caused by the presence of a soluble circulating antigen (Ag) that provokes and combines with antibody (Ab). As these Ag-Ab complexes reach a critical size, they are deposited in the glomerular membranes of the kidney. upon deposition, an acute inflammatory reaction occurs because of complement activation. Bee-sting and penicillin allergies are examples of IgE mediated anaphylactic reactions. Contact dermatitis is mediated by T cells, not antibody.

8. HLA antigens are found on: A. All nucleated cells B. Red Blood cells only C. solid tissue only D. White blood cells only

A. All nucleated cells Human leukocyte antigens (HLAs) are a group of antigen originally describe on human white cells. It is known that they are found on all nucleated cells of the body, including solid tissue cells. HLAs are not found on red blood cells.

26. In individuals allergic to pollen, hyposensitization protocols may be initiated. These individauals receive injections of : A. Allergen B. Pooled human antisera C. Monoclonal antibody directed against human T cells D. Monoclonal antibody directed against human B ells

A. Allergen Hyposensitization, allergy injections, involves the administration of gradually increasing concentrations of an allergen. The goal is for the patient to become tolerant of the allergen and no longer exhibit an allergic response to the allergen. It is hypothesized that patients will ultimately develop high concentrations of IgG to the allergen, blocking IgE from binding and thereby preventing the allergic reaction.

100. A 38 year old woman visited her physician because of fatigue, fever and joint pain (proximal interphalangeal, wrist and knee joints). She also noticed sensitivity to the sun and reported having a rash following recent exposure. the physician noted a rash over her nose and cheeks. Lab results included white blood cell count 5.5x10^9/L (reference range 4.8-10.8x10^9/L) and RBC count of 4.5x10^12/L (reference range 4.0-5.4x10^12/L). Urinalysis results were within reference ranges, except for 4+ protein and 1+ RBCs, 0-3 hyaline casts/lpf and 0-1 RBC cast/lpf on microscopic examination. Which of the following tests would be most helpful in diagnosing this patient's condition? A. Anti-nuclear antibody B. alpha-fetoprotein C. Anti-streptolysin O D. Hepatitis profile

A. Anti-nuclear antibody The presence of arthritis is suggestive a number of autoimmune diseases. Protein, RBCs, and casts in the urine are indicative of kidney inflammation. These signs and symptoms along with the rash on the face are characteristic of SLE. A commonly used sensitive screening test for SLE is the ANA test. The ANA, however, is not specific for SLE. If the ANA were positive, additional autoantibody tests specific for SLE (e.g., anti-Smith) should be performed.

35. A major advantage of passive immunization compared to active immunization is that: A. Antibody is available more quickly B Antibody persists for the life of the recipient C. IgM is the predominant antibody class provided D. Oral administration can be used

A. Antibody is available more quickly In passive immunization, preformed antibody is delivered to the recipient, making the antibody available immediately. In active immunization, a period of days is required before antibody production occurs. Passive immunity is short lived, in contrast to the possibly lifelong persistence of actively induced antibody. Because passive immunization involves the transfer of antibodies, the oral route cannot be used - antibodies are digested in the GI tract. The antibodies administered by passive immunization consist largely of the IgG class.

39. The type of immunity that follows the injection of an immunogen is termed: A. Artificial active B. Natural active C. Artificial passive D. Innate

A. Artificial active Active immunity follows exposure to an antigen that stimulates the recipient to develop his or her own immune response. Vaccines are an example of artificial immunity in that the animal was exposed to the immunogen by the actions of a healthcare provider. Surviving infections can result in natural active immunity. Protection is due to the formation of memory cells.

54. Loss of self-tolerance results in: A. Autoimmune disease B. Graft-versus-host desease C. Immunodeficiency D. Tumors

A. Autoimmune disease The immune system recognizes hosts cells as self and is tolerant to antigens on those cells. The loss of tolerance will result in an autoimmune disease in which the immune system mounts an immune response against self cells. Graft versus host disease occurs when a bone marrow graft is incompatible with the host tissues and attacks the host.

49. IgM antibodies react well in complement fixation (CF) tests. Because of this, CF tests for antibodies should: A. Be positive early in the course of the disease B. Be useful in identifying antibodies responsible for a delayed hypersensitivity reaction C. Be useful in identifying antibodies responsible for anaphylactic reactions D. Detect transplacental antibodies

A. Be positive early in the course of the disease In most infections, IgM antibodies will develop first followed by IgG, which develop higher titers and are longer lasting. Anaphylactic reactions are caused by IgE antibody. Delayed hypersensitivity reactions are caused by T cells. Transplacental antibodies belong to the IgG class. IgG antibodies, although they can be detected by complement fixation (CF), do not fix complement efficiently.

73. The alternative complement pathway: A. Can be activated by bacterial capsule polysaccharides B. Uses C5b as a C3 convertase C. Bypasses steps C3 through C5 D. Is inactivated by properdin

A. Can be activated by bacterial capsule polysaccharides The alternative pathway for complement activation is a more nonspecific defense mechanism, in that it does not require the presence of antibody for activation. It can be activated by a variety of substances, including complex polysaccharides found in bacterial capsules and cell walls. These materials activate C3 directly. Properdin protein stabilizes some of the active complement proteins, and C4b2a is a C3 convertase.

61. The activity of natural killer (NK) cells: A. Does not require previous exposure to an antigen B. Involves phagocytosis and killing of bacteria C. Requires interaction with cytotoxic T cells D. Requires interaction with B cells

A. Does not require previous exposure to an antigen The natural killer (NK) cells destroy target cells through an extracellular nonphagocytic mechanism. NK cells are part of the host's innate resistance and, therefore, do not need previous exposure to an antigen to be active. They also do not need interaction with B or cytotoxic T cells.

1. Color Plate 21 ("Y" shaped, right portion of the "Y" prong), depicts a monomeric immunoglobulin molecule. The portion of the molecule indicated by the dotted red circle and the red arrow is called the: A. Fab fragment B. Fc fragment C. Heavy chain D. Hinge region

A. Fab fragment The basic structure of all immunoglobulins is two light chains jointed to two heavy chains by disulfide bonds. The amino terminus of both the heavy and light chains, together, constitutes the Fab fragment (fragment of antigen binding). The carboxy terminus of the heavy chains constitutes the Fc fragment. The hinge region is the area at the center of the "Y," near the carboxyterminus of the light chains.

5. Monocytes and macrophages play a major role in the mononuclear phagocytic system. For an antibody-coated antien to be phagocytized, what part of the antibody molecule fits into a receptor on the phagoytic cell? A. Fc region B. Fab region C. Hinge region D. Variable region

A. Fc region The Fc region of an IgG molecule fits into an Fc receptor (FcR) on macrophages and monocytes. The Fc receptor binds to specific amino acid residues in the Fc region of the immunoglobulin. The variable region of immunoglobulin binds to the antigen.

91. B lymphocytes and T lymphocytes are derived from: A. Hematopoietic stem cells B. Macrophages or monocytes C. Mucosa-associated lymphoid tissue D. The fetal liver

A. Hematopoietic stem cells The stem cells of the bone marrow give rise to both T and B cells, as well as other cells in the bloodstream. Macrophages and monocytes also arise from hematopoietic stem cells, but they do not differentiate into lymphocytes. Mucosa associated lymphoid tissue contains mature lymphocytes, particularly B cells, but is not the source of lymphocytes. The fetal liver is maturation site for B lymphocytes during fetal life but is not the source of those lymphocytes.

16. Color plate 22 (center of a dimeric IgA molecule) represents a dimeric IgA molecule. The structure printed in red and indicated by the red arrow is called the: A. J-piece B. Hinge region C. Heavy Chain D. Light Chain

A. J-piece IgA is found in mucous secretions as a dimer stabilized by the J-piece. IgA is synthesized locally by plasma cells and dimerized intracellularly. IgM is also held together by a J-piece, but it exists as a pentamer.

95. In a chemiluminescent immunologic assay, what is the signal detected? A. Light B. An electric signal C. A purple-colored compound D. A yellow-colored compound

A. Light In chemiluminiscent assays, light is the end product. These assays require special instruments to measure the light emitted in the reaction. Chemicals used to generate light include luminol and luciferase.

79. What is the indicator system used in the complement fixation test? A. Sensitized sheep red blood cells B. Fluorescent-labeled antihuman globulin C. Enzyme-labeled antihuman globulin D. Guinea pig complement

A. Sensitized sheep red blood cells The first step in the complement fixation test, the test system, involves the reaction of antibody in the patient's serum to the corresponding antigen in the presence of guinea pig complement. If antibody antigen binding occurs, complement will bind to the immune complexes. The second step is the addition of sensitized sheep red blood cells (the indicator system). If complement bound to the immune complexes in the first step, it is not available to lyse the sensitized red blood cells. If antibody was not present in the patient sample, complement will not bind to the immune complexes, and it will be free to lyse the sensitized cells.

93. In a competitive radioimmunosorbent test (RIST), what does a high signal suggest? A. The patient sample has a low concentration of IgE B. The patient sample has a low concentration of IgM C. The patient sample has a high concentration of IgE D. the patient sample has a high concentration of total antibody

A. The patient sample has a low concentration of IgE The competitive RIST assay is used to determine the concentration of total IgE. Patient sample containing IgE is mixed with labeled IgE. Both labeled and unlabeled IgE are captured by antihuman IgE. After a wash step, the signal from the label is detected. A high signal indicates a low concentration of unlabeled IgE from the patient sample.

53. Elevated IgE levels are typically found in A. Type I hypersensitivity reactions B. Type II hypersensitivity reactions C. Type III hypersensitivity reactions D. Type IV hypersensitivity reactions

A. Type I hypersensitivity reactions Elevated IgE levels are found in type I hypersensitivity reactions. The antibody bind via the Fc portion of the molecule to Fc receptors on mast cells and basophils. When the attached antibody binds its specific allergen, the cell degranulates.

32. A molecule found in human serum sometimes used as a tumor marker is: A. alpha-fetoprotein B. HBsAg C. Biotin D. CD1

A. alpha-fetoprotein AFP and carcinoembryonic antigen (CEA) are oncofetal antigens that become expressed after malignant transformation. Approximately 70% of patients with primary hepatoma have elevated levels of AFP. However, the major use of determining AFP levels is in monitoring patients undergoing cancer treatment.

80. The isotype of an immunoglobulin antibody A. is defined by the heavy chain B. Is defined as different alleles of the same antibody type (e.g. IgG) C. Is constant for all immunoglobulins of an individual D. Is the variation within the variable region

A. is defined by the heavy chain The isotype of an antibody is determined by which heavy chain is present. The term "idiotype" refers to the variable region of an immunoglobulin molecule. The variable region is the portion of immunoglobulin that binds antigen. Every immunoglobulin with a given antigenic specificity has a unique idiotype.

72. In the classical pathway of complement activation, A. C3 is activated by binding C-reactive protein B. The sequence of activation is C1, C2, C3, C4 C. C1q is activated by the presence of a single Fab region D. Activation by antibody requires one IgM or two IgG molecules

D. Activation by antibody requires one IgM or two IgG molecules Complement attaches to the Fc portion of the antibody molecule. At least two Fc binding sites are required for C1q to attach. Therefore, activation requires two IgG molecules or a single molecule of IgM, which is a pentamer. The C proteins were named in order of discovery. The correct reaction sequence is C1, C4, C2, C3. As the last step of this reaction sequence, C3 split into C3a and C3b.

42. The agglutination pattern shown in Color Plate 23 was observed while performing an antibody titration. this agglutination pattern is and example of: A. A prezone reaction B. A prozone reaction C. A postzone reaction D. Incomplete complement inactivation

B. A prozone reaction Prozone occurs when an extremely high titer of antibody is present. In the first tubes of the titration, not enough antigen is present to allow for cross linking and lattice formation. The antibody effectively blocks all the antigen sites present, so agglutination does not occur. Complement is not involved in antibody titration.

4. A lymphokine is: A. A soluble mediator produced by granulocytes and affecting lymphocytes B. A soluble mediator produced by lymphocytes C. A soluble mediator produced by plasma cells D. An antibody that reacts with lymphocytes

B. A soluble mediator produced by lymphocytes Lymphokines are soluble mediators of immune reactions. They are produced most often by T lymphocytes. Antibodies are produced by plasma cells.

97. An 11 year old female presents with fever, sore throat, lethargy, and tender cervical lymphadenopathy. Relevant findings include splenomegaly and lymphocytosis, with many large reactive (atypical) lymphocytes. A heterophile antibody test was negative. Further laboratory results were as follows: CMV: IgG titer= 20; IgM titer=0 EBV VCA: IgG titer= 0; IgM titer=80 Mono spot: IgG titer= 0; IgM titer=0 What conclusion can be made concerning the diagnosis? A. Acute CMV infection B. Acute EBV infection C. Chronic CMV infection D. Chronic EBV infection

B. Acute EBV infection The symptoms of fever of unknown origin, lymphocytosis, and lymphadenopathy suggest EBV of CMV infection and lymphoma or leukemia. Heterophile antibodies become positive later than antibodies to viral core antigens (VCA) of EBV. In addition, only about 50% of children less than 12 years of age form heterophile antibodies following EBV infection. The IgM titer of 80 for EBV is consistent with acute EBV infection.

31. Diagnosis of group A streptococci (Streptococcus pyogenes) infection is indicated by the presence of: A. Anti-protein A B. Anti-DNase B C. Anti-beta-toxin D. C-reactive protein

B. Anti-DNase B The serological diagnosis of group A streptococcal infection can be made by demonstrating anti-DNase B. The antistreptolysin O (ASO) assay can also be used; however, ASO response is poor in skin infections. CRP is an acute phase protein indicating inflammation.

64. The primary mechanism responsible for pathology in systemic lupus erythematosus is: A. Allergic reaction to foreign molecules B. Antibodies directed against self antigens C. Polycolonal activation of cytotoxic T cells D. Lack of intracellular killing after neutrophil phagocytosis of bacteria

B. Antibodies directed against self antigens Antibodies directed against self antigens form immune complexes and activate complement. Circulating immune complexes, composed of nuclear antigen and antinuclear antibody, deposit in various organ systems, activate complement, and produce organ pathology. T cells are not directly involved in this process. Allergens, phagocytosis, and killing of ingested bacteria by neutrophils do not play a role in the pathogenic process.

50. Which of the following serologic tests is commonly performed by an immunofluorescence method? A. Anti-HBs B. Antinuclear antibody (ANA) C. Antistreptolysin O (ASO) D. C-reactive protein (CRP)

B. Antinuclear antibody (ANA) Testing for antinuclear antibodies (ANAs) is commonly performed by the immunofluorescence method - using fluorescein conjugated antibody to detect patient antibody bound to nuclear components of test cells. Antistreptolysin O tests are performed with red cells or, more recently, by latex agglutination. Anti-HBs assays are generally performed by ELISA, and CRP assays are generally performed by latex agglutination, turbidimetry, or nephelometry.

36. The strength with which a multivalent antibody binds a multialent antigen is termed: A. Affinity B. Avidity C. Reactivity D. Valence

B. Avidity "Avidity" is used to describe the strength of binding between a multivalent antibody and multivalent antigen. "Affinity" describes the bond between a single antigenic determinant and an individual combining site. "Valence" refers to the number of antigenic determinants on an antigen.

38. After activation of the complement system, leukocytes and macrophages are attracted to the site of complement activation by: A. C1 B. C5a C. C8 D. IgM

B. C5a The complement activation product C5a is chemotactic for neutrophils and macrophages. Neither C1 nor C8 (which occur in the plasma before complement activation) possesses such chemotactic properties. IgM antibody, although capable of activating complement by the classical pathway, is not a chemotactic factor for phagocytic cells.

89. In patients with human immunodeficiency virus infection, immune status can be monitored by measuring the ratio of: A. CD3+ cells to CD8+ cells B. CD4+ cells to CD8+ cells C. Lymphocytes to monocytes D. T cells to B cells

B. CD4+ cells to CD8+ cells Human immunodeficiency virus preferentially infects T helper cells, which are positive for the surface marker CD4. As the infection progresses, the number of CD4+ cells in the peripheral bloodstream decreases. CD8 is a marker found on another subset of T cells, cytotoxic T cels. The reference ratio of CD4:CD8 cells is 2:1. A decrease in the ratio indicates a decline in immune function.

24. Multiple myeloma is a: A. Lymphoproliferative disease of T cells B. Cancer of plasma cells characterized by increased antibody concentration C. Lymphoproliferative disease resulting in a decrease in antibody production D. Cancer of monocytes characterized by increased kappa and lambda chain synthesis

B. Cancer of plasma cells characterized by increased antibody concentration Plasma cells are normally end stage cells; they live a few days and die. During MM, plasma cells become cancerous and continue to secrete antibody. The cells also secrete excess light chains that can be found in the urine; these proteins are called Bence Jones proteins.

7. The HLA complex is located primarily on: A. Chromosome 3 B. Chromosome 6 C. Chromosome 9 D. Chromosome 17

B. Chromosome 6 The HLA system is part of a larger region known as the major histocompatibility complex. It is located on chromosome 6. The region is located on the short arm of the chromosome. Chromosome 15 contains one HLA gene, B2M.

18. Type I hypersensitivity is: A. Associated with complement mediated cell lysis B. Due to immune complex deposition C. Mediated by activated macrophages D. An immediate allergic reaction

D. An immediate allergic reaction Type I hypersensitivity reactions occur immediately after second exposure to an allergen. On the firs, or primary, exposure, IgE specific to the allergen is produced. The IgE binds to Fc receptors on the surface of basophils and mast cells. Immune complexes and complement are not involved in the response.

52. In the enzyme-linked immunosorbent assay (ELISA), the visible reaction is due to a reaction between: A. Enzyme and antibody B. Enzyme and substrate C. Fluorescent dye and antigen D. Latex particles and antibody

B. Enzyme and substrate The indicator system in an ELISA test consists of an enzyme and its substrate. If the enzyme labeled antibody has complexed with the immobilized antigen, the addition of substrate will produce a colored end product. Alkaline phosphatase is an enzyme frequently used in ELISA tests. Latex particles, fluorescent dyes, and red blood cells are not used in ELISA tests but in other test methodologies.

45. The veneral disease research laboratory (VDRL) test for syphilis is classified as a(n): A. Agglutination reaction B. Flocculation reaction C. Hemagglutination reaction D. Precipitation reaction

B. Flocculation reaction The cardiolipin antigen is particulate, not soluble, in the VDRL test. However, the particles are too small to make macroscopic agglutinates when combined with antibody. This type of reaction is called a flocculation reaction and needs to be read with low power microscopy.

78. A serum sample is positive for HBsAg. This results indicates that the person from whom the serum was taken: A. Had a hepatitis B infection in the past but overcame the infection B. Has either active or chronic hepatitis B infection C. Was immunized recently against the hepatitis B virus D. Is no infectious for the hepatitis B virus

B. Has either active or chronic hepatitis B infection Hepatitis B surface antigen (HBsAg) is a marker for active or chronic infection by the hepatitis B virus; it indicates ongoing viral replication. A person positive for this marker is infectious. If the person had overcome a past infection, he or she would have antibody to the surface antigen (anti-HBs) but not the surface antigen. Immunization causes formation of anti-HBs antibody, and the surface antigen would not be present in serum.

14. Which class of immunoglobulin possesses delta heavy chains? A. IgA B. IgD C. IgE D. IgG

B. IgD The heavy chains divide human immunoglobulin molecules into separate classes and subclasses. The delta heavy chain corresponds to IgD. The remaining classes IgA, IgE, IgG, and IgM corresponds to alpha, epsilon, gamma, and mu, respectively.

71. Which of the following statements about the test for C-reactive protein (CRP) is true? A. It correlates with neutrophil phagocytic function B. It is an indicator of ongoing inflammation C. It is diagnostic for rheumatic fever D. Levels decrease during heart disease

B. It is an indicator of ongoing inflammation CRP is an acute phase reactant. Although it is elevated in inflammation, its presence is not diagnostic for any one disease, such as rheumatic fever. It does not correlate with antibody levels or with neutrophil phagocytic function. CRP levels are sometimes elevated during heart disease.

69. Which of the following complement proteins is part of the membrane attack complex? A C1 B. C3 C. C4 D. C5

D. C5 The membrane attach complex forms following the binding of C5 to a biologic membrane. The complex is formed by the sequential addition of C6, C7, C8, and C9. When C5-C8 complex with C9, a tubule is formed that bridges the cell membrane.

25. Which one of the following decribes a direct immunofluorescence assay? A. Conugated reagent antigen reacts with antibodies to form antigen-antibodycomplexes B. Antigens reacts with unlabeled antibody forming antigen-antbody complexes that attach to labeled antibodies C. A dye is attached to a molecule and it reacts with an immune complex to produce a color D. Conjugated reagent antibody reacts with antigen to form antigen-antibody complexes

D. Conjugated reagent antibody reacts with antigen to form antigen-antibody complexes In a direct immunofluorescence assay, a fluorescent molecule is linked to an antibody. This complex is often called a conjugate. Clinical material is fixed onto a microscope slide, and the conjugate is added. After a wash step, the slide is examined with a microscope using UV light. If antigen specific to antibody was present in the clinical specimen, fluorescence will be seen.

51. The Fab portion of an antibody: A. Binds T cell receptor B. Consists of two light chains only C. Consists of two heavy chains only D. Contains the hypervariable reagion

D. Contains the hyper variable reagion The Fab portion of an antibody contains the hypervariable region. This portion of the molecule has a variable sequence of amino acids that affects the three dimensional structure of the molecule and, therefore, determines the specificity (idiotype) of the antibody. This region contains the amino terminal portion of the two light chains and the two heavy chains.

55. A human cell with CD8 on its surface is most likely a: A. B cell B. Monocyte C. T helper cell D. Cytotoxic T cell

D. Cytotoxic T cell The CD8 molecule is found primarily on cytotoxic T lymphocytes. T helper cells possess CD4 on their surface, as do several other cell types. CD3 is a marker found on most T cells.

63. Which of the following is a characteristic of T cells? A. Synthesize antibody B. Mature in the thymus C. Able to bind unprocessed antigen D. Primarily protect against extracellular parasites

B. Mature in the thymus T cells are produced in the bone marrow and mature in the thymus. Plasma cells, not T cells, produce antibody, and T cells can only react to antigen processes by an antigen presenting cell. The cell mediated immune response, which requires the activity of T cells, is primarily helpful in fighting against intracellular parasites.