Micro chapter 12
MHC I proteins interact with ____ cells, whereas MHC II proteins interact with ____ cells.
CD8+; CD4+
2 main Tc (t cytokine) cells
CD8+; act as effector t-cells - function: kills cells infected by virus, damaged, cancerous, foreign
Which of the following cell surface structures may initiate B cells by T-independent antigens?
Capsules
High levels of IgM antibodies indicate __________ in a patient.
recent exposure to a pathogen or antigen
__________ immunity is mediated by the production and activation of T cells.
Cellular
Which type of cell directly attacks infected cells?
Cytotoxic T-cells
HIV directly infects T-cells. Why is this problematic for cell-mediated immunity?
Cytotoxic T-cells begin to attack the virally infected T-cells, reducing the number of T-cells in the body
__________ bind to B cell receptors (BCR) and T cell receptors (TCR).
Epitopes
secondary response
second exposure to antigen -IgM: 7 days - IgG 14 days
Which of the following molecules released by cytotoxic T cells will enter a virus-infected cell through pores and break down proteins?
Granzymes
The degree to which the antigen provokes an immune response varies and depends on the antigen's biochemical features. Which of the following molecules are the least immunogenic?
Haptens
Immune cells that secrete cytokines and activate other immune cells are:
Helper T-cells
How do helper T-cells and cytotoxic T-cells work together?
Helper T-cells produce cytokines to activate other cells of the immune system.
__________ immunity is the branch of adaptive immunity that produces antibodies.
Humoral
Place the stages of adaptive immunity in order from first to last. I. Antigen elimination and memory II. Lymphocyte activation III. Antigen presentation IV. Lymphocyte proliferation and differentiation
III, II, IV, I
All antibody isotypes can appear as a monomer, but only __________ can appear as a dimer.
IgA
Which of the following antibodies is found primarily on the mucous membranes?
IgA
Which of the following immunoglobulins is primarily involved in allergic responses?
IgE
Your patient has an anaphylactic response to bee venom. Which of the following classes of antibodies would you expect to be elevated in the patient's serum, based on this hypersensitivity?
IgE
__________ antibodies fight parasites and mediate allergic responses.
IgE
Which of the following antibodies can cross the placenta and is the most abundant of all antibodies?
IgG
Which of the following antibodies is the most abundant antibody type?
IgG.
Which of the following antibodies can appear as a pentamer and occurs first after exposure to antigen?
IgM
Antibody titers during the primary exposure to an antigen consist primarily of:
IgM antibodies.
_________can exist as either a monomer or a snowflake-shaped pentamer and is central to _________.
IgM; agglutination and precipitation reactions
__________ immunity is immediate, and it responds in the same way to every microbial threat.
Innate
What type of antigen typically binds to MHC I to present an MCH I-antigen complex?
Intracellular antigen
Which of the following most accurately describes the advantage of isotype switching
Isotype switching expands the operational capacity of antibodies.
A newly-generated T cell can recognize MHCs and is not self-reactive. What is its fate?
It will migrate to the lymphoid tissues to await activation by its antigen.
Cellular and humoral responses both progress through four main stages. What is the second stage?
Lymphocyte activation
The main proteins that are matched between a tissue donor and recipient are the __________ proteins.
MHC
What is the role of MHC I in the immune response?
MHC I is found on all body cells except red blood cells and presents a sample of cellular proteins, including those of any intracellular pathogens, to T cells
T-dependent antigens require T helper cells to interact with the __________ molecule and co-stimulatory proteins on the plasma membrane of B cells to activate the B cell.
MHC II
Each of the following components is found on the "Y" shaped antibody molecule
MHC II molecules.
As T cells develop, they are screened for reaction to __________ to assure self-tolerance.
MHC or HLA molecules
Which proteins on the antigen-presenting cell are recognized by the helper T-cell?
MHC proteins
When "matching" a donated organ or tissue to a recipient, it is necessary that the ________ of the donor and the recipient be as similar as possible.
MHCs
Which of the following are not part of the adaptive immune system?
Neutrophils
characteristics of the primary immune response?
Nonspecific response to a pathogen or antigen Immediate response to a pathogen or antigen Does not involve specialized cells
Where are MHC I receptor molecules found?
On the surface of all body cells except red blood cells
Which of the following statements concerning T cell self-tolerance screening is true?
Once T cells pass the self-tolerance screening, they migrate to lymphoid tissues.
Which of the following is not a key antibody function?
Phagocytosis
Antibodies are secreted from which type of cell?
Plasma cells
Which of the following is not a result of activation of the complement cascade by antibodies?
Precipitation
An activated T helper cell becomes either an effector T helper cell or a memory T helper cell. What is the function of the effector T helper cell?
Release factors that help T cytotoxic cell and B cell activation
Humoral Response
Stage 1: B-cells are antigen presenting cells -b-cell receptors bind to intact/extracellular antigens, which may or may not be endocytosed/processed Stage 2: b-cells are activated by t-dependent or t-independent antigens 1) t-dependent antigen required for activation (most are long term) 1) B-cell receptors bind to antigen 2) processed antigen presented by MHC II 3) Th binds 4) tH releases cytokines 2) t-independent antigen: don't require th -b-cell receptors binds to antigen (polysaccharide) Stage 3: activate b-cells proliferation and differentiation -proliferation: clonal expansion= production of cell clones -differentiation: memory cells and effector cells (=plasma cells)
___________include a variety of bacterial toxins (e.g. staphylococcal enterotoxins and staphylococcal toxic shock toxin) and are especially potent T helper cell activators.
Superantigens
Which of the following statements is true regarding superantigens?
Superantigens trigger the release of high levels of inflammatory cytokines, such as tumor necrosis factor alpha and interferon gamma by CD4 T cells.
The human immunodeficiency virus (HIV) selectively infects any cell which carries the CD4 surface glycoprotein. Which immune function will be impaired?
stimulation of macrophage, B and TC cells
The secondary signal in T cell activation is necessary for:
T cell subclass specialization
Cellular adaptive immunity is mainly carried out by ________
T cytotoxic cells
Which of the following T cell classes directly destroys infected or cancerous cells?
T cytotoxic cells
The cellular response is favored when __________ cells develop.
T helper 1 (TH1)
Which of the following T cell classes activate natural killer cells and macrophages?
T helper 1 (TH1) cells
When __________ develop, the humoral immune response is favored.
T helper 2 (TH2) cells
Which of the following T cell classes stimulates B cells to make antibodies?
T helper 2 (TH2) cells
Which of the following is the primary activation signal to fully activate T helper cells?
T helper cell's TCR interacts with the MHCII-antigen complex.
In the cellular branch of adaptive immunity, __________ organize the response.
T helper cells
The most abundant class of T cells are __________.
T helper cells
_________ are the most abundant T cells, and their function is to __________.
T helper cells (CD4+); coordinate the adaptive immune response
An APC bearing MHC-antigen complexes on its cell surface migrates to lymphoid tissues and interacts with which of the following cells?
T helper cells and T cytotoxic cells
__________ retain the ability to recognize specific epitopes after the pathogen has been cleared by the immune system.
T memory (Tmemory) cells
Which of the following T cell classes reduces the adaptive response once the threat passes?
T regulatory (Treg) cells
Cellular Branch of adaptive immunity stage 3
T-cell proliferation and differentiation - proliferation: clonal expansion=production cell clones - cytokines produced from stage 2 affect what subclass of t-cell (th or tc) develops -Th1: cellular response - Th2: humoral response - differentiation: memory and effector cells (Th and Tc subclasses)
Which of the following is NOT a subclass of TH cells?
TC
Which receptor on the helper T-cell recognizes the specific antigen from an antigen-presenting cell?
TCR
Natural killer cells are activated by
TH1 cells.
Which of the following cells CANNOT be an antigen-presenting cell?
t cells
T-cells recap
Th: -Th1 -Th2 -Treg -effectors Tc: -effecors: get rid of antigens
Which of the following best describes antibody titer?
The amount of antibody present in the blood
Cellular Branch of adaptive immunity stage 2
t-cells are activated by antigen presenting cell in lymphatic tissue -because more than one antigen can be displayed by antigen presenting cells more than one t-cell can combine - It takes two signals to lead to the activation of t-cells 1) primary activation signal: t cells receptor:MHC:antigens interact 2) secondary activation signal: co-stimulatory protein on t-cell and antigen presenting cell - function: specialized t-cell (subclass)
Displayed antigen fragments by antigen-presenting cells (APCs) are recognized by
t-helper cells
Which cell recognizes and kills self-cells altered by infection
tc cells
Which cell releases cytokines and stimulates B cells?
th2
T-helper cells are activated by the TCR interacting with the MHC molecule and:
the B7 protein on the APC's cell surface with CD28 on the surface of T cells.
T cytotoxic cells are activated by the TCR interacting with the MHC molecule and:
the CD8 receptor interacting with an MHC I-antigen complex.
the following explain why natural and artificial active immunity provide long-term protection?
The host produces antibodies against the antigen or pathogen. The host produces memory cells against the antigen or pathogen. The host produces activated B and T cells against the pathogen.
Analysis of a patient's blood indicates high levels of IgG antibodies. This indicates that:
the patient is in the late stages of an infection or has had previous exposure to the antigen.
Genetic mutations in the CD8a gene often result in a CD8 T cell deficiency. Which of the following scenarios would be most likely to occur in a patient with several CD8a gene mutations?
This patient would be less able to respond to certain viral invaders, such as Epstein Barr Virus.
All of the following are true regarding natural killer (NK) cells EXCEPT
they destroy infected body cells by phagocytosis.
How is the immune system able to recognize a limitless number of different antigens and epitopes?
While each lymphocyte carries receptors that recognize only one type of epitope, the immune system produces a wide variety of lymphocytes each of which carries unique receptors.
The monomeric structure of an antibody can be described as ________-shaped and is composed of light and heavy chains that are held together by _________.
Y; disulfide bridges
Antibody titers during the secondary response to a pathogen or antigen are:
a surge of IgG with a small titer of IgM.
Contracting an infection or receiving __________ confers long-term immunity.
a vaccination
Antibodies are involved in ______ immunity.
adaptive and humoral
Third line defenses
adaptive immunity is acquired through infection or vaccination primary response: first encounter with antigen secondary response: later encounter; faster more effective memory component
Antibodies increase phagocytosis through each of the following mechanisms
agglutination precipitation opsonization
Isotype switching:
alters the subtype of antibody that is made.
increased affinity
antibodies bind better to antigen (secondary response)
As B cells are screened, B cells are eliminated when they produce _________
antibodies reacting to self-antigens
epitope
antigen determinant (smaller part of antigen) - part of antigen reconized by immune cells
4 stages with humoral response
antigen presented 1 B-cells 2 communication between b and t cells of cellular response 3 clonal expansion effector cells 4 production of antibodies
4 stages with cellular response
antigen presenting cells 1 t-cells 2 release cytokines to activate t-cells 3 clonal expansion (proliferation) and memory effector cells (differentiation) 4 effector cells
Each of the following determines immunogenicity
antigen size. chemical composition. molecular complexity.
Your patient is suffering from botulism caused by the potent toxin released by Clostridium botulinum. In addition to supportive care, the patient could also receive an ________ to neutralize the toxin and stimulate her _________.
antitoxin; artificially acquired passive immunity
Antigens
any substance that triggers the immune system (immunogenic ) ex: large- microbial or viral proteins; polysaccharides -small: abnormal molecules on cancer cells - allergens: dust, pollen, environmental chemicals
Vaccines produce:
artificial active immunity.
Pregnant women are usually advised to be vaccinated against influenza to protect themselves and the baby after birth. The mother will acquire ________ immunity from the vaccine while the baby will acquire ________ immunity.
artificial active; natural passive
Treatment of a patient with antiserum is an example of:
artificial passive immunity
Immunization is an example of
artificially acquired active immunity
T cells mature in the __________.
thymus
B cells mature in the __________.
bone marrow
two branches
cellular (t-cells) mediated Humoral (B-cells or Ab-mediated response)
Superantigens can be all of the following except:
cholera toxin.
After T helper and T cytotoxic cells are stimulated by APCs, these cells then undergo:
clonal expansion.
T helper cells release _____ to activate B cells.
cytokines
Each of the following describes adaptive immunity
delayed specific memory
The most active of the antigen-presenting cells (APCs) are __________.
dendritic cells
Superantigens activate T helper cells by:
directly linking the MHC and the TCR.
T-cell receptor and B-cell receptor
each t-cell and b-cell are different - a single t or b cell has around 100,000 identical antigen receptors on its surface due to DNA rearrangement (gene shuffling ) of R genes
Cellular Branch of adaptive immunity stage 4
effector t-cells eliminate antigens; memory t-cells remain in lymph tissue or spleen -Tc cytokine: seek and destroy cells (MHCI: antigen/cancerous) Interferons: stimulate the recruitment of Tc cytokine and the production of MHCI (increases the likelihood of displaying antigen) Tc cytokine release: 1) cytokines to attract natural killer cells and macro 2) performance (Form pores) 3) granzymes (break down proteins and stimulate apoptosi) -Th helper support action of other white blood cells (tc, macro, natural killer,b-cells)
Extracellular pathogens are engulfed within a(n) ________, which fuses with a(n) __________ before pieces of the antigens associate with MHC II molecules, after which they are displayed on the plasma membrane.
endocytic vesicle; lysosome
Isotype switching
epitope stays the same but the immunoglobulin can switch (ex: G to A) to sue cytokines made by Th2 Isotype switching deals with IgM and IgT
The parts of an antigen that B and T cells recognize and mount an immune response against are called _________.
epitopes
The parts of an antigen that the immune system responds to are known as __________.
epitopes
primary response
first exposure to antigen; first to act is IgM - IgM: 14 days - IgG: 21 days
Immunological memory provides all of the following protections
generation of primarily IgG antibodies. coordinated activity of B and T cells. rapid reactivation of humoral and cellular adaptive response.
When B or T cells become encounter an antigen, they proliferate and produce __________.
genetically identical cells
If bone marrow cells are transplanted, an improper match between donor and host can result in __________.
graft-versus-host disease
Molecules that are unable to stimulate an immune response without being combined with a larger molecule are __________.
haptens
The two-signal activation process for T cells includes
interaction of the T-cell receptor with the MHC-antigen complex on the APC AND binding between co-stimulatory proteins on the T cell and APC surfaces.
CD8 T cell activation occurs through _______, involving presentation of antigen with _______.
intracellular antigen presentation; MHC I molecule
The major histocompatibility complex type I (MHC I) _________.
is found on all body cells except red blood cells
What is the role of B cell receptors (BCRs) and T cell receptors (TCRs) in the immune response?
to recognize specific epitopes of an antigen
In order for a T cell to become activated, it must receive __________ signal(s) from an antigen-presenting cell.
two
if a B or T cell reacts to self-antigens, it:
undergoes cell suicide (apoptosis).
5 antibody isotypes
- IgG (monomer): most toxins and viruses; cross placenta -IgA (monomer or dimer): surface or mucus membrane; milk; resistance to stomach acid -IgM (monomer or pentamer): first to appear upon infection; first made by babies -IgE (monomer): allergies; parasites -IgD (monomer): poorly understood
Cellular Branch of adaptive immunity stage 1
- Stage 1: APCs use MHC I or MHCII to present Ag to t-cells MHCI: 1) surface of all cells 2) present intracellular, antigen (ex: virus) 3) bind with CD* of t cytokine 4) activate t cytokine ti kill infected cell - can also apply to abnormal MHCI as in cancer MHCII: 1) surface of antigen presenting cells (phago, B) 2) present extracellular antigen (ex: bacterium ) 3) bind with CD4 of t helper 4) activate t helper
Self-tolerance
- a large number of different T cell receptors and b cell receptors are made - our body wants only those that don't target self; need to be self tolerant - T-cells are screened in thymus - t cell receptors must recognize protein (MHC protein) of self cells because MHC display antigens to t-cells -B-cells are screened in bone marrow - b cell receptors can't make antibodies (secreted BCRs) against self cells
Adaptive immunity
- specific host defenses -invertebrates only
immune responses.
-Adaptive immunity is specific to a particular antigen, while innate immunity is not. -Adaptive immunity has a memory component, while innate immunity does not. -Adaptive immunity takes longer to respond than innate immunity.
true statements
-Antibodies activate classical complement cascades. -B cells usually require T cells for full activation. -T cytotoxic cells directly combat antigens.
Which of the following statements regarding B lymphocytes is/are true?
-B lymphocytes are both produced and mature in the bone marrow. -Once activated, B lymphocytes have the ability to produce antibodies.
Which of the following statements is/are true regarding T cytotoxic cell antigen elimination?
-Following apoptosis by cytotoxic T cells, macrophages and natural killer cells clear the dead cells. -Interferons released by infected or cancer cells attract and activate cytotoxic T cells, while cytokines released by the cytotoxic T cells attract natural killer cells and macrophages. -Once the threat has been detected by the T cell receptor, the cytotoxic T cell releases perforins that form pores in the target cell and granzymes, which enter through pores to trigger apoptosis.
Which statements are true about MHC II?
-MHC II primarily displays extracellular antigens which have been phagocytized. -When bound to antigen, MHC II serves a key role in activation of the appropriate T cells. -MHC II interacts with the CD4 receptor on T helper cells -MHC II is present only on antigen-presenting cells
T cell class with its description?
-TH: identified by the CD4 proteins on the cell surface -TH1: stimulate TC cells -TH2: stimulate B cells to make antibodies -Treg: ensures that immune responses subside once a threat subsides
Which of the following statements accurately differentiates the adaptive immune system and the innate immune system?
-Unlike the innate immune system, the adaptive immune system is characterized by memory and specificity. -Unlike the innate immune system, the adaptive immune system includes both a cellular and humoral response
Antibodies do all the following
-activate the complement cascade. -neutralize antigens to prevent binding to host cells. -increase phagocytosis by agglutination of antigens. -increase phagocytosis by opsonization.
Naturally aquired immunity
-active: individual benefits from antibodies made from previous infections - passive: is not making antibodies but still benefits (placenta to newborn)
Artificially aquired immunity
-active: vaccinations; benefit from antibodies -passive: antivenom or tetanus shot
MHC: major histocompatibility complex
-found in virtually all vertebrates - humans, MHC: HLA (human leukocyte antigen) -MHC I: all cells present intracellular antigen; bind to CD8 t cytokine - MHC II: Antigen presenting cells (APC) present extracellular antigen (CD4 t helper) (phago, B)
All the following apply to T cells
-mature in the thymus. -originate in the bone marrow. -have the capacity to recognize virtually any type of antigen. -reside in the lymphoid tissue.
What are the two types of cells recruited upon cytotoxic T cell activation?
macrophages and natural killer cells
All the following apply to B cells
-originate in the bone marrow. -coordinate the humoral response by making antibodies. -reside in the lymphoid tissue. -mature in the bone marrow.
2 classes of T-cells
1) Th cells: (helper) CD4+ (CD=cluster diff) - function: to coordinate adaptive immune response -release cytokines to active macro, B, T cytokine cells Subclasses of helper t-cells: effector helper t-cells -Th1: cytokines activate t cytokine cells, macro, natural killer cells -Th2: cytokines stimulate B-cells> antigen presenting cells -Trags: cause immune response to be reduced
4 stages of adaptive immunity
1) antigen presentation 2) activating lymphocyte 3) proliferation and differentiation 4) getting rid of antigens and production of memory
Antigens can be:
1) complete 2) incomplete (haptens )
antibody: antigen interaction
1) neutralization 2) complement system activation which results in cytolysis, opsonization, inflammation 3) increased phagocytosis via: precipitation, agglutination, opsonization
Put the following antigens in order from most to least immunogenic: 1. Haptens 2. Polysaccharides 3. Lipids 4. Proteins
4, 2, 3, 1
Your pediatric patient recently received a DTaP vaccination, providing immunity to diphtheria, tetanus, and pertussis. If your patient is exposed to pertussis a few weeks following this vaccination, which of the results would you expect to receive when measuring the patient's antibody titers?
A rapid surge in the production of IgG antibody
Indicate whether the following describes humoral immunity or cellular immunity.
A. Immunoglobulins bind to intact antigens.: humoral B. Lymphocytes bind to processed antigens.: cellular C. Lymphocytes mature in the thymus.: cellular D. Lymphocytes mature in the red bone marrow.: humoral E. Lymphocytes secrete cytokines.: cellular F. Lymphocytes secrete antibodies.: humoral
Contracting an infection creates:
natural active immunity.
antibodies in colostrum to protect the newborn or antibodies that cross the placenta to protect the fetus confer:
natural passive immunity.
A patient fully recovered from Ebola with minor medical support. This was the result of ____________.
naturally acquired active immunity
A mother is breastfeeding her infant son and transferring crucial antibodies to him. This will result in _________.
naturally acquired passive immunity
Antibodies protect against the tetanus toxin through __________.
neutralization
Which branch of the immune system produces antibodies?
Adaptive humoral response
When do helper T-cells develop into TH1 or TH2 cells?
After proliferation into a clonal population
Similar to the need for a primary activation signal to fully activate T helper cells, a primary activation signal is needed to activate B cells by T-dependent antigens. Which of the following serves as the primary activation signal
An extracellular antigen binds to a B cell receptor
Which of the following scenarios would result in long-term immunity? To be marked correct, you'll need to select all applicable statements, as there may be more than one correct answer.
An otherwise healthy individual developing antibodies against Epstein-Barr virus following a case of mononucleosis A healthy individual receiving an MMR vaccination
Each T cell and B cell has thousands of receptors, and each receptor can bind to __________ epitope(s).
one
MHC I molecules display all of the following antigen types except:
parasitic worm antigens.
All of the following types of antigens are presented by MHC II molecules
parasitic worm antigens. extracellular bacteria. fungal antigens.
Which cell produces antibodies?
plasma cells
T-independent antigens are usually repetitive_________ molecules that stimulate B cells to produce antibodies.
polysaccharide
What are the three ways in which antibodies can increase phagocytosis?
precipitation, aggulation, opsonization
Consider a genetic mutation which causes T helper cells to be unable to respond to stimulation by the cytokines which lead to TH2 differentiation. This mutation would cause a patient to be deficient in which activity?
production of antibodies
Which of the following molecules are only found as part of the humoral immune response?
Antibodies
__________, or amount of antibody present in the blood, is _________ during the secondary immune response.
Antibody titer; greater
What is an antigen?
Any molecule that, when presented in the right context, will stimulate an immune response
Which of the following accurately and completely describes an antigen?
Any substance that can trigger an immune response
Viral proteins are broken down in the __________ and carried to the _________ before being displayed on MHC I-antigen complexes on the surface of the cell.
proteasome; endoplasmic reticulum
TH2 cells produce cytokines that activate
B cells
Which type of cell directly binds an antigen, rather than requiring an antigen-presenting cell to first process the antigen?
B cells
During clonal selection,
B cells differentiate into plasma cells and memory cells.
Which of the following is a common feature between T and B cells?
Both produce memory cells after activation.
