MHC

Question 1

Exogenous antigen includes all of the following EXCEPT
a. bacterial toxins.
b. extracellular protozoan parasites.
c. most bacteria.
d. ragweed pollen.
e. viruses.

Answer 1

e. viruses.

Question 2

Human Class I MHC a chain molecules are
a. b2-microglobulin.
b. H-2 D, K, and L.
c. H-2 IA and IE
d. HLA-A. -B, and -C.
e. HLA-DR, -DP, and -DQ.

Answer 2

d. HLA-A. -B, and -C.

Question 3

Cells which have MHC Class II are ________, which present ________antigen to Th cells.
a. antigen presenting cells, endogenous
b. antigen presenting cells, exogenous
c. infected cells, inflammatory
d. target cells, endogenous
e. target cells, exogenous

Answer 3

b. antigen presenting cells, exogenous

Question 4

Signaling to a cytotoxic T cell that a liver cell is infected with hepatitis virus depends on
a. binding of Ii to Class I MHC until the peptide is loaded.
b. binding of TCR on the cytotoxic T cell to Class II MHC on the infected cell.
c. binding of processed antigen to liver cell Class I MHC.
d. processing the hepatitis virus peptides to the correct size and anchor residues in the endosomal pathway.
e. both c and d are correct.

Answer 4

c. binding of processed antigen to liver cell Class I MHC.

Question 5

Endogenous antigen presentation requires delivery of antigen peptides to the endoplasmic reticulum by
a. Class I MHC and invariant chain.
b. calnexin and tapasin.
c. HLA-DM.
d. leader sequence.
e. TAP-1 and TAP-2.

Answer 5

e. TAP-1 and TAP-2.

Question 6

Following virus infection, peptides produced from the proteasome are more likely to be presented on the surface of the target cell because
a. MHC Class I is synthesized in response to virus infection.
b. proteasomal enzymes which produce shorter peptides are synthesized in response to virus infection.
c. TAP-1 and TAP-2 specifically bind virus peptides.
d. virus amino and carboxyl terminal amino acids bind better to Class I MHC than peptides from self proteins.
e. virus infection induces expression of proteases which cut proteins at sites which bind best to TAP-1 and TAP-2.

Answer 6

e. virus infection induces expression of proteases which cut proteins at sites which bind best to TAP-1 and TAP-2.

Question 7

Exogenous antigen is processed
a. after presentation by antigen presenting cells.
b. by nearly every nucleated cell.
c. by the cytosolic processing pathway.
d. in the presence of b2-microglobulin.
e. in acidified endosomes.

Answer 7

e. in acidified endosomes.

Question 8

Class II MHC does not efficiently present endogenous antigen because
a. antigen synthesized inside the cell never makes it to the endosomal compartment.
b. endogenous antigen cannot be processed into peptides small enough.
c. HLA DM transports Class II to the surface before it can bind endogenous peptide.
d. invariant chain blocks binding of endogenous peptide in the ER.
e. phagocytosed antigen binds Class II as rapidly as Class II is synthesized.

Answer 8

d. invariant chain blocks binding of endogenous peptide in the ER.

Question 9

MIIC is a specialized intracellular compartment where
a. HLA DM promotes the release of CLIP and peptide binding to Class II MHC.
b. invariant chain binds to Class II MHC a and b chains.
c. peptides are transported into the ER for binding to Class II.
d. proteins are broken down into peptides by proteasomes.
e. some pathogens live protected from lysosomal enzymes.

Answer 9

a. HLA DM promotes the release of CLIP and peptide binding to Class II MHC.

Question 10

In order to have pathogen peptide plus Class II MHC molecules expressed on the membrane of host cells, all of the following are required EXCEPT
a. b2-microglobulin.
b. CLIP.
c. HLA-DM.
d. HLA-DR, -DP, and -DQ alpha chains.
e. Ii .

Answer 10

a. b2-microglobulin.

Question 11

Invariant chain (Ii)
a. inhibits binding of endogenous peptide to Class I MHC.
b. is degraded in the MIIC compartment to CLIP.
c. is released from Class II upon binding of b2-microglobulin.
d. is the constant region of Class I peptide binding site.
e. prevents exogenous peptide binding to Class II MHC in the ER.

Answer 11

b. is degraded in the MIIC compartment to CLIP.

Question 12

Antigen binding by Class I MHC molecules
a. accommodates many different peptides.
b. preferentially occurs for peptides 13-18 amino acids in length.
c. occurs at a site on Class I MHC formed by folding of a1 and b2-microglobulin domains.
d. occurs only on antigen presenting cells.
e. takes place at the plasma membrane of the infected cell.

Answer 12

a. accommodates many different peptides.

Question 13

Both Class I and Class II MHC molecules are
a. composed of a and b chains with variable and constant regions.
b. expressed constitutively on all nucleated cells.
c. expressed on the B cell membrane.
d. part of the T cell receptor for antigen.
e. synthesized in response to antigen processing.

Answer 13

c. expressed on the B cell membrane.

Question 14

The major histocompatibility complex has
a. dozens of loci for Class I and Class II proteins.
b. genes that encode proteins associated with antigen processing.
c. only genes encoding Class I and Class II molecules.
d. single loci for Class I and Class II proteins.
e. three regions encoding Class I, Class II, and Class III receptors.

Answer 14

b. genes that encode proteins associated with antigen processing.

Question 15

MHC polymorphism
a. is generated by recombination of HLA A, B, and C gene segments.
b. is present primarily in the peptide-binding regions of MHC proteins.
c. is the result of random association of many alpha and beta genes.
d. restricts the ability of B cells to bind antigen.
e. results in expression of dozens of MHC alleles on each APC.

Answer 15

b. is present primarily in the peptide-binding regions of MHC proteins.

Question 16

T cells are MHC-restricted in their ability to respond to antigen because
a. all antigen must be processed and presented to activate lymphocytes.
b. during an infection, all cells in the body present antigen on MHC Class I.
c. MHC binds antigen more specifically than TCR does.
d. TCR must recognize both antigen and MHC molecules.
e. the T cells should not respond to antigen on allogeneic cells.

Answer 16

d. TCR must recognize both antigen and MHC molecules.

Question 17

Linkage of a disease to an HLA allele means that
a. everyone with that allele will eventually get the disease.
b. people with that allele have a higher risk for the disease.
c. the MHC protein encoded by that allele is defective.
d. the allele will eventually disappear from the population.
e. None of the above is true.

Answer 17

b. people with that allele have a higher risk for the disease.

Question 18

All of the following are associated with the expression of Class I MHC molecules EXCEPT
a. antigen peptide presentation on membrane Class I MHC to Tc.
b. graft rejection.
c. increased risk of certain autoimmune diseases.
d. lysis of virus-infected cells.
e. stimulation of antibody production.

Answer 18

e. stimulation of antibody production.

Question 19

Human Class II MHC molecules
a. are encoded by the genes HLA-A, B, and C.
b. are found on all nucleated cells.
c. have an antigen binding site formed from regions of two polypeptide chains.
d. must be associated with b2-microglobulin molecules to bind peptide.
e. present antigen to CD8 cytotoxic T cells.

Answer 19

c. have an antigen binding site formed from regions of two polypeptide chains.

Question 20

Humans inherit from each of their parents
a. a random set of MHC Class I, Class II, and Class III genes.
b. enough diversity in MHC to present epitopes from most pathogens.
c. enough diversity in MHC to present every possible antigen epitope.
d. genes for a and b chains that can be recombined to increase their diversity.
e. the same Class I and Class II MHC genes as their siblings.

Answer 20

b. enough diversity in MHC to present epitopes from most pathogens.

Question 21

The a chain of HLA-DR
a. can be expressed with the b chain of any MHC molecule.
b. can be expressed with the b chain of any Class II MHC molecule.
c. can be expressed with the b chain of any Class II DR molecule.
d. must be expressed with b2-microglobulin.
e. must be expressed with the b chain of Class II DR from the same chromosome.

Answer 21

c. can be expressed with the b chain of any Class II DR molecule.

Question 22

Which of the following statements is TRUE?
a. Each individual expresses all the diversity of MHC protein structure.
b. If a family has four children, no two of them will have the same MHC genotype.
c. Someone with bare lymphocyte syndrome who expressed no MHC proteins would die in infancy.
d. TCR on Tc cells binds a1 and b2 domains of Class I MHC protein.
e. The chances of finding a tissue match are much higher between children and their parents than between siblings.

Answer 22

c. Someone with bare lymphocyte syndrome who expressed no MHC proteins would die in infancy.

Question 23

Which of the following statements is FALSE?
a. All MHC alleles in the population have been counted.
b. CD4 T cells see antigen on self Class II MHC but not on self Class I MHC.
c. Human Class II MHC proteins are called HLA DP, HLA DQ, and HLA DR.
d. Class I and Class II MHC are less antigen-specific than Ig.
e. Peptides presented by Class I MHC must be 8-10 amino acids long.

Answer 23

a. All MHC alleles in the population have been counted.

Question 24

Which of the following statements is FALSE?
a. A peptide binding to Class I must have certain amino- and carboxyl-terminal amino acids to bind tightly to the ends of the Class I binding cleft.
b. A transplant is most likely to be successful between people who share the same alleles at all Class I and Class II MHC loci.
c. Identical twins share all their Class I and Class II MHC alleles.
d. Peptide binding to TCR is influenced by both its own conformation and the conformation of the MHC protein to which it is bound.
e. The gene for b2-microglobulin is in the Class I region of the MHC.

Answer 24

e. The gene for b2-microglobulin is in the Class I region of the MHC.