This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Structure and Function of MHC Molecules”.
1. MHC molecules are the set of genes that code cell surface proteins essential for _________
a) Innate immunity system
b) Adaptive immunity system
c) Both innate and adaptive systems
d) Coding for proteins is not a function of MHC molecules
View Answer
Explanation: Major Histocompatibility Complex molecules or simply MHC molecules code for those proteins which play role in adaptive immune system to recognize pathogens.
2. Which of the following cells recognize the antigens present on the cell surface of the MHC molecules?
a) T cells
b) B cells
c) Mast cells
d) Macrophages
View Answer
Explanation: Major histocompatibility complexes are present on both B cells and T cells. The antigens recognized by the MHCs are presented to T cells.
3. Which of the following co-receptors recognizes the beta2 microglobulin subunit of class I MHCs?
a) CD24
b) CD4
c) CD8
d) CD16
View Answer
Explanation: Class I MHCs have microglobulin subunits alpha1, alpha2, alpha3 and beta2. Among these, beta2 is recognised by CD8 co-receptors.
4. Which of the following co-receptors recognizes the beta1 and beta2 microglobulin subunits of class II MHCs?
a) CD24
b) CD4
c) CD8
d) CD16
View Answer
Explanation: Class II MHCs have microglobulin subunits alpha1, alpha2, beta1 and beta2. Among these, beta1 and beta2 are recognised by CD4 co-receptors.
5. In class I MHCs, which two subunits form the binding cleft?
a) Alpha1 and Alpha2
b) Alpha1 and Alpha3
c) Alpha3 and Beta2
d) Alpha1 and Beta2
View Answer
Explanation: Alpha1 and alpha2 microglobulin subunits form the peptide cleft in class I MHCs. Peptide clefts are the sites of polymorphism in MHCs. Their main function is to present intracellular proteins to CTLs.
6. In class II MHCs, which two subunits form the binding cleft?
a) Alpha1 and Alpha2
b) Alpha1 and Alpha3
c) Beta1 and Beta2
d) Alpha1 and Beta1
View Answer
Explanation: Alpha1 and beta1 microglobulin subunits form the peptide cleft in class II MHCs. The antigenic peptide is positioned in this peptide cleft which is recognized by T helper cells
7. In humans, what are MHCs called as ________
a) HHC
b) HLA
c) HAT
d) HPFC
View Answer
Explanation: In humans, MHCs are known as HLAs, Human Leukocyte Antigens. These are present/located on the short arm of chromosome 6. These HLAs are actually controlled and driven by all the genes present on chromosome 6.
8. Which of the following does the class III MHC code for?
a) T helper cells
b) T cytotoxic cells
c) T regulatory cells
d) Complement proteins
View Answer
Explanation: Class III MHC molecules code for complement proteins. They also code for some other components of complement system such as cytokines and heat shock proteins.
9. Class I MHC has three genes, HLA-A, HLA-B and HLA-C. Which of the following is the correct order of level of polymorphism?
a) A > B > C
b) B > A > C
c) A > C > B
d) B > C > A
View Answer
Explanation: Among the three alleles of class I MHCs, HLA-B is more polymorphic than HLA-A and HLA-A is more polymorphic than HLA-C which means HLA-B has many different alleles compared to others.
10. Class II MHCs have 6 genes in its system.
a) True
b) False
View Answer
Explanation: Class II MHCs have 6 genes, they are HLA-DP-alpha, HLA-DP-beta, HLA-DQ-alpha, HLA-DQ-beta, HLA-DR-alpha and HLA-DR-beta, where each one of these are expressed in codominant way.
11. Which of the following genes of class II MHCs is most polymorphic?
a) HLA-DP-alpha
b) HLA-DP-beta
c) HLA-DR-beta
d) HLA-DR-alpha
View Answer
Explanation: Because of the property of the DR-beta’s extra beta chain to pair up with the DR-alpha chain, it is more polymorphic than the other genes.
12. MHC molecules exhibit ______________ property.
a) Allelic exclusion
b) Somatic hypermutation
c) Co-dominant expression
d) Clonal expansion
View Answer
Explanation: Expression of MHC molecules is co-dominant because of both the alleles being at the same loci and being expressed at the same time and also being able to present antigens.
13. At what angle does the TCR sit on the MHC molecules?
a) 30°
b) 45°
c) 60°
d) 90°
View Answer
Explanation: The T cell receptor sits on the MHC molecule at an angle of 45° so that it can touch both the MHC and the peptide at the same time which is kind of the whole point as to ensure the proper interaction.
14. Class II MHCs are found only on APCs.
a) True
b) False
View Answer
Explanation: Yes, class II MHcs are found only on APCs, i.e., antigen presenting cells which are B cells, macrophages and dendritic cells, whereas class I and class III MHCs are present on all cells.
15. When T cells respond to a non-self MHC, it is called __________
a) Alloreactivity
b) Isoreactivity
c) Alloavidity
d) Isoavidity
View Answer
Explanation: Alloreactivity is the property of t cells responding to the non-self MHCs. Because of this it clears itself as a transplant rejection and GVHD, a disease that is caused due to allogeneic transplant.
Sanfoundry Global Education & Learning Series – Immunology.
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