Exam 2: Practice Set 3

Question 1

The first immunoglobulin heavy chain class to be expressed on the surface of a newly produced B-cell is:
A. IgA 
B. IgD 
C. IgE 
D. IgG 
E. IgM

Answer 1

The correct answer is E.
IgM is the first immunoglobulin class to be expressed on the surface of the developing B-cells, shortly followed by IgD. Early mature B-cells co-express IgM and IgD antibodies of identical antigen specificity.

Question 2

A B-cell is able to make cell-surface and secreted versions of antibody using:
A. Different gene pools.
B. Differential splicing.
C. Different heavy chain class but the same light chain.
D. Different light chain class but the same heavy chain.
E. F(ab’)2 fragments.

Answer 2

The correct answer is B.
Differential (alternative) splicing of a primary RNA transcript can produce antibody either with or without exons encoding a hydrophobic transmembrane sequence which leads to retention of antibody in the cell surface membrane.

Question 3

The cytoplasmic region of surface IgM consists of:
A. A single H chain constant region domain.
B. A light chain.
C. 110 amino acids.
D. 3 amino acids.
E. Carbohydrate.

Answer 3

The correct answer is D.
This is too short to directly transmit a signal into the cell following antigen binding, a function carried out by the Ig-alpha and Ig-beta accessory molecules.

Question 4

The percentage of human peripheral blood T-cells bearing a gamma delta T-cell receptor is:
A. 30–80%.
B. 1-5%.
C. 100%.
D. 0%.
E. Only present during mycobacterial infections.

Answer 4

The correct answer is B.
Although they constitute a minority of the peripheral blood T-cells in man, gamma delta T-cells are more heavily represented in intestinal epithelium and in skin.

Question 5

A chromosome on which T-cell receptor alpha chain gene rearrangement has occurred lacks which of the following gene segments:
A. Joining (J).
B. Diversity (D).
C. Variable (V).
D. Constant (C).
E. TCR beta chain.

Answer 5

The correct answer is B.
The T-cell receptor alpha chain genes do not possess D gene segments, although the delta chain genes do. However, because the delta chain locus is found entirely within the alpha chain locus and is located between the V alpha and the J alpha gene segments, any alpha chain gene rearrangements lead to the loss of the delta chain gene segments, including all of the D delta segments.

Question 6

Expression of MHC genes is:
A. Codominant.
B. Dominant for maternal genes.
C. Dominant for paternal genes.
D. Dependent on thymic selection.
E. Totally dependent on the antigenic exposure of the individual.

Answer 6

The correct answer is A.

The MHC molecules encoded by both parental genes are expressed.

Question 7

The molecules mediating signal transduction following antigen binding to cell surface immunoglobulin on a B-cell are called:
A. IgFc
B. Ig-alpha and Ig-beta
C. MHC
D. CD4
E. CD8

Answer 7

The correct answer is B.
Ig-alpha and Ig-beta possess C-terminal cytoplasmic regions which become phosphorylated upon cross-linking of membrane immunoglobulin, leading to a rapid mobilization of intracellular calcium.

Question 8

The T-cell receptor for antigen is:
A. Derived from the immunoglobulin gene pool by alternative splicing.
B. A tetramer.
C. A homodimer.
D. A heterodimer.
E. A single chain molecule.

Answer 8

The correct answer is D.
There are two versions of the T-cell receptor, both of which are heterodimers consisting of an alpha chain and a beta chain, or a gamma chain and a delta chain.

Question 9

The T-cell receptor antigen recognition signal is transduced by:
A. The TCR alpha chain.
B. The TCR beta chain.
C. CD1.
D. CD2.
E. CD3.

Answer 9

The correct answer is E.
CD3 is a molecule composed of five polypeptide chains (CD3-gamma, -delta, and - epsilon plus zeta-zeta, eta-eta or zeta-eta), which transduces the antigen recognition signal received by the T-cell receptor heterodimer to the inside of the cell.

Question 10

MHC class II molecules are found on:
A. Virtually all cells in the body.
B. B cells, dendritic cells and macrophages.
C. Only gamma-interferon activated cells.
D. Virtually all nucleated cells in the body.
E. Only on virally-infected cells.

Answer 10

The correct answer is B.

These cells are able to present processed endogenous antigen to CD4+ T-cells.

Question 11

The following is characteristic of B- but not T-cells:
A. Class I MHC.
B. CD3.
C. Measles virus receptor.
D. Polyclonal activation by concanavalin A.
E. Surface immunoglobulin.

Answer 11

The correct answer is E.
B-cells express surface immunoglobulin of a specificity created by that cell’s particular immunoglobulin gene recombination. A totally different gene set encodes the T-cell receptor for antigen.

Question 12

When a resting naive T-cell engages its specific MHC/peptide complex displayed on the surface
of a fibroblast it:
A. Undergoes blast cell formation.
B. Produces IL-2.
C. Moves from Go to G1 of the cell cycle.
D. Becomes anergic.
E. Secretes IL-1.

Answer 12

The correct answer is D.

In the absence of costimulator, a cell becomes anergic and incapable of subsequent response to the specific antigen.

Question 13

The T-cell ligand binding B7 on a professional antigen-presenting cell is:
A. CD28
B. CD2
C. LFA-1
D. ICAM-1
E. VCAM-1

Answer 13

The correct answer is A.

An alternative ligand for B7, present on activated T-cells, is CTLA-4.

Question 14

Protein tyrosine kinase activity following T-cell stimulation:
A. Phosphorylates and thereby activates phospholipase C gamma 1.
B. Is an inherent property of the T-cell receptor alpha and beta chains.
C. Is an inherent property of CD3.
D. Is unaffected by herbimycin A.
E. Is unrelated to phosphorylation of the CD3-associated zeta chains.

Answer 14

The correct answer is A.
The tyrosine kinase activates the phospholipase, which accelerates the hydrolysis of phosphatidylinositol 4,5-diphosphate to diacylglycerol and inositol 1,4,5-triphosphate.

Question 15

The early increase in phospholipase C gamma 1 activity following T-cell stimulation:
A. Represents a sensitive regulatory negative feedback control mechanism.
B. Dephosphorylates protein tyrosine kinase inhibitors.
C. Accelerates hydrolysis of diacylglycerol.
D. Accelerates hydrolysis of phosphatidylinositol diphosphate.
E. Accelerates hydrolysis of inositol triphosphate.

Answer 15

The correct answer is D.

The enzyme splits phosphatidylinositol diphosphate to diacylglycerol and inositol triphosphate.

Question 16

The nuclear AP-1 site responsible for 90% of IL-2 enhancer activity binds:
A. The Oct – 1 transcriptional factor.
B. The Fos/Jun transcription factors.
C. The nuclear factor of activated T-cells (NFAT).
D. The NF-kappa B transcriptional factor.
E. Polyclonal mitogenic agents such as concanavalin A.

Answer 16

The correct answer is B.

The MAP kinase JNK phosphorylates Jun, which then binds as a binary complex with Fos to the AP-1 site.

Question 17

In the immunological synapse:
A. The acetylcholine receptor in expressed on the T-cell.
B. Production of substance P by the antigen-presenting cell is a key event.
C. The initial interaction between TCR and MHC is unstable.
D. Adhesion molecule pairs eventually move to the center of the synapse.
E. The B7–CD28 interaction is redundant.

Answer 17

The correct answer is C.
One of the main functions of the immunological synapse is thought to be to cement the initially unstable interactions between TCR and MHC in order that optimal activation of the T-cell can occur.

Question 18

T-cell help for antibody production:
A. Depends on T-cell recognition of native antigen bound to B-cell surface Ig.
B. Depends on T-cell recognition of antigen processed by the B-cell.
C. Involves class I MHC on the B-cell.
D. Can occur in X-irradiated mice.
E. Is a feature of the antibody response to pneumococcal polysaccharide.

Answer 18

The correct answer is B.
The native antigen binds to B-cell surface Ig, is taken inside the cell, processed and the peptide placed as a complex with class II MHC on the cell surface where it is recognized by T-helper cells.

Question 19

Cross-linking of B-cell surface receptors:
A. Is a characteristic feature of thymus-dependent antigens.
B. Lowers the intracellular Ca++ concentration.
C. Rapidly phosphorylates the Ig-alpha and Ig-beta chains of the surface Ig receptor.
D. Requires contiguity of 2 B-cell epitopes of different specificity on the same antigen molecule.
E. Cannot be achieved by anti-idiotypic antibodies.

Answer 19

The correct answer is C.
Within one minute of surface Ig ligation there is rapid phosphorylation of the Ig-alpha and Ig-beta chains and a subsequent rise in intracellular calcium.

Question 20

Activation of resting B-cells by T-helpers depends directly upon costimulatory interaction between:
A. CD40 and CD40L.
B. B7 and CD28.
C. B7 and CTLA-4.
D. CD4 and MHC class II.
E. ICAM-1 and LFA-1

Answer 20

The correct answer is A.
Costimulatory signals arising from the interaction of CD40 on the resting B-cell with CD40L (CD40 ligand, CD154) on the activated T-helper cell ensure effective B-cell activation.

Question 21

The T-cell receptor link to MHC/peptide is enhanced by interaction between MHC class II on the antigen-presenting cells with the following molecule on the T-cell:
A. LFA-1
B. CD2
C. CD4
D. CD8
E. CD28

Answer 21

The correct answer is C.
CD4 on helper T-cells binds to the non-polymorphic part of the MHC class II molecule.

Question 22

The main costimulatory signal for activation of resting T-cells is provided by ligation of:
A. CD28
B. Surface Ig
C. LFA-1
D. VLA-4
E. IL-2

Answer 22

The correct answer is A.
B7 (CD80 and CD86) on the antigen-presenting cell ligating CD28 on the T-cell provides the main costimulatory signal for the activation of resting T-cells.

Question 23

Which one of the following events occurs earliest in T-cell signaling:
A. Activation of phospholipase C.
B. Activation of protein kinase C.
C. Production of inositol triphosphate.
D. Activation of protein tyrosine kinase.
E. Mobilization of intracellular calcium

Answer 23

Correct D.
Activation of protein tyrosine kinase activity is responsible for subsequent activation of membrane components by phosphorylation.

Question 24

T-cell CD40L provides a costimulatory signal to B-cells by ligating:
A. Surface Ig
B. MHC class II
C. CD28
D. CD19
E. CD40

Answer 24

The correct answer is E.
The costimulatory signal provided by the CD40L/CD40 interaction is necessary for the activation of resting B-cells by helper T-cells. Note that CD40L is the abbreviation for CD40 ligand, which is also known as CD154.

Question 25

Cytokines always act:
A. By binding to specific receptors.
B. In an autocrine fashion.
C. At long range.
D. Antagonistically with other cytokines.
E. Synergistically with other cytokines.

Answer 25

The correct answer is A.
The cell-type specificity of cytokines is provided by the regulated expression of specific cytokine receptor genes. Many cytokine receptors consist of more than one polypeptide. For example, the IL-2 receptor is composed of an alpha chain (CD25) of low affinity and a beta chain of intermediate affinity; when both are expressed together they form the high affinity IL-2 receptor.

Question 26

A Cytokine receptor which is a member of the hematopoietin receptor family is:
A. IL-8 receptor.
B. IFN gamma receptor.
C. TNF (TNF-alpha) receptor.
D. IL-1 receptor.
E. IL-2 receptor.

Answer 26

The correct answer is E.
The hematopoietin receptor family contains a large number of members each of which comprises one or two polypeptide chains responsible for cytokine binding and an additional shared (common) chain involved in signal transduction.

Question 27

The alpha/beta heterodimeric form of the IL-2 receptor:
A. Is downregulated on activated cells.
B. Binds IL-2 with high affinity.
C. Is found only on T-cells.
D. Uses CD45 as an alpha chain.
E. Allows rapid dissociation of bound IL-2.

Answer 27

The correct answer is B.
The alpha beta heterodimeric form of the IL-2 receptor has an affinity (Kd) of 10-11 M (10 pm), whereas the alpha chain alone binds IL-2 with low affinity, and the beta chain alone with medium affinity.

Question 28

IFN-gamma and TNF (TNF alpha) can act synergistically:
A. To downregulate expression of MHC class I.
B. Because IFN-gamma downregulates expression of TNF receptors.
C. To upregulate expression of MHC class II.
D. Because they both bind to the same receptor.
E. Because they cross-link IFN-gamma and TNF beta receptors.

Answer 28

The correct answer is C. 
There is synergism between IFN-gamma and TNF in the upregulation of surface MHC class II molecules on, for example, cultured pancreatic insulin-secreting beta cells.

Question 29

Which of the following is characteristically produced by the Th2 CD4 cells which provide help for antibody production, but not by Th1 cells?
A. IFN-gamma
B. Lymphotoxin (TNF-beta)
C. GM-CSF
D. IL-4
E. IL-1

Answer 29

The correct answer is D.

IL-4, together with IL-5, IL-6, IL-10 (mouse only) and IL-13 is characteristically produced by Th2 cells.

Question 30

Dendritic cells can be driven from a resting state to an activated state by the T-cell surface molecule:
A. TCR 
B. CD40L 
C. CD28 
D. B7
E. CD40

Answer 30

CD40 ligand (CD154) on the T-helper cell engages CD40 on the resting dendritic cell, resulting in upregulation of costimulatory molecules such as B7 on the now activated dendritic cell.