Q.1 What is the primary function of Major Histocompatibility Complex (MHC) molecules?
Transport oxygen in blood
Present antigens to T cells
Produce antibodies
Engulf pathogens
Explanation - MHC molecules are responsible for presenting processed antigens to T cells, enabling the adaptive immune response.
Correct answer is: Present antigens to T cells
Q.2 Which MHC class presents antigens to CD8+ cytotoxic T cells?
MHC Class I
MHC Class II
MHC Class III
MHC Class IV
Explanation - MHC Class I molecules present endogenous antigens to CD8+ T cells, which are cytotoxic T lymphocytes.
Correct answer is: MHC Class I
Q.3 Which cells primarily express MHC Class II molecules?
Red blood cells
All nucleated cells
Antigen-presenting cells (APCs)
Neurons
Explanation - MHC Class II molecules are expressed mainly on professional APCs such as dendritic cells, macrophages, and B cells.
Correct answer is: Antigen-presenting cells (APCs)
Q.4 MHC molecules are encoded by genes located on which chromosome in humans?
Chromosome 6
Chromosome 14
Chromosome 12
Chromosome 21
Explanation - In humans, the MHC genes, also called HLA genes, are located on the short arm of chromosome 6.
Correct answer is: Chromosome 6
Q.5 Which of the following is NOT a classical MHC molecule?
HLA-A
HLA-B
HLA-C
HLA-DM
Explanation - HLA-DM is a non-classical MHC molecule involved in peptide loading of MHC Class II molecules, not directly presenting antigens.
Correct answer is: HLA-DM
Q.6 Endogenous antigens are typically presented by which MHC class?
MHC Class I
MHC Class II
MHC Class III
MHC Class IV
Explanation - Endogenous antigens from within the cell, such as viral proteins, are presented by MHC Class I molecules.
Correct answer is: MHC Class I
Q.7 Which MHC class molecule is recognized by CD4+ helper T cells?
MHC Class I
MHC Class II
MHC Class III
MHC Class IV
Explanation - MHC Class II molecules present antigens to CD4+ T helper cells, initiating immune activation.
Correct answer is: MHC Class II
Q.8 Which of the following MHC molecules is highly polymorphic?
MHC Class I
MHC Class II
Both Class I and Class II
MHC Class III
Explanation - Both MHC Class I and II molecules exhibit high polymorphism, which increases the diversity of antigen presentation.
Correct answer is: Both Class I and Class II
Q.9 Which type of antigen do MHC Class II molecules usually present?
Endogenous
Exogenous
Viral DNA
Self-proteins only
Explanation - MHC Class II molecules present exogenous antigens, typically derived from extracellular pathogens engulfed by APCs.
Correct answer is: Exogenous
Q.10 Which non-classical MHC molecule is involved in presenting lipid antigens?
HLA-A
HLA-B
CD1
HLA-DQ
Explanation - CD1 molecules are non-classical MHC molecules that present lipid and glycolipid antigens to T cells.
Correct answer is: CD1
Q.11 The MHC restriction principle refers to:
T cells recognizing antigens only with self-MHC molecules
Antibodies binding to MHC molecules
MHC genes being inherited together
MHC molecules producing cytokines
Explanation - T cells recognize peptide antigens only when presented by self-MHC molecules, which is the basis of MHC restriction.
Correct answer is: T cells recognizing antigens only with self-MHC molecules
Q.12 Which region of MHC Class I molecule binds peptides?
α1 and α2 domains
α3 domain
β2-microglobulin
Transmembrane domain
Explanation - The peptide-binding groove of MHC Class I molecules is formed by the α1 and α2 domains.
Correct answer is: α1 and α2 domains
Q.13 Which component stabilizes MHC Class I molecules on the cell surface?
CD8
β2-microglobulin
TAP protein
Invariant chain
Explanation - β2-microglobulin associates with MHC Class I heavy chain to stabilize the molecule for antigen presentation.
Correct answer is: β2-microglobulin
Q.14 The invariant chain is associated with which MHC class?
MHC Class I
MHC Class II
MHC Class III
CD1
Explanation - The invariant chain binds MHC Class II in the ER and guides it to endosomal compartments for peptide loading.
Correct answer is: MHC Class II
Q.15 Which transporter protein delivers peptides into the ER for MHC Class I loading?
TAP
TCR
CD4
Invariant chain
Explanation - TAP (Transporter associated with Antigen Processing) translocates peptides into the ER for binding to MHC Class I molecules.
Correct answer is: TAP
Q.16 Which MHC Class II molecule is involved in peptide editing?
HLA-DR
HLA-DP
HLA-DQ
HLA-DM
Explanation - HLA-DM facilitates the removal of CLIP and proper loading of peptides onto MHC Class II molecules.
Correct answer is: HLA-DM
Q.17 Which of the following is a feature of non-classical MHC molecules?
Highly polymorphic
Limited tissue distribution
Present endogenous peptides only
Found on all nucleated cells
Explanation - Non-classical MHC molecules often have restricted expression and specialized roles, unlike classical MHC molecules.
Correct answer is: Limited tissue distribution
Q.18 Cross-presentation refers to:
MHC Class I presenting exogenous antigens
MHC Class II presenting endogenous antigens
T cells recognizing self-antigens
Antibodies binding to T cells
Explanation - Cross-presentation allows exogenous antigens to be presented on MHC Class I molecules, enabling activation of CD8+ T cells.
Correct answer is: MHC Class I presenting exogenous antigens
Q.19 Which MHC molecules are involved in transplant rejection?
Only Class I
Only Class II
Both Class I and Class II
Non-classical MHC only
Explanation - Both MHC Class I and II molecules are recognized as foreign in transplants, leading to immune-mediated rejection.
Correct answer is: Both Class I and Class II
Q.20 Which cytokine upregulates MHC Class II expression on APCs?
IL-4
IFN-γ
TNF-α
IL-10
Explanation - IFN-γ is a key cytokine that induces the expression of MHC Class II molecules on antigen-presenting cells.
Correct answer is: IFN-γ
Q.21 HLA typing is important for:
Diagnosing infections
Matching donors and recipients for transplantation
Measuring antibody levels
Detecting T cell activation
Explanation - HLA (MHC) typing ensures compatibility in organ and bone marrow transplantation to minimize rejection.
Correct answer is: Matching donors and recipients for transplantation
Q.22 Which statement is TRUE about MHC polymorphism?
It reduces diversity of antigen presentation
It increases susceptibility to all infections
It allows presentation of a wider variety of peptides
It occurs only in Class III genes
Explanation - Polymorphism in MHC genes ensures that different individuals can present different sets of peptides to T cells, enhancing immune defense.
Correct answer is: It allows presentation of a wider variety of peptides
Q.23 Which domain of MHC Class II molecule interacts with CD4 molecule on T cells?
α1
α2
β2
β2 domain
Explanation - The β2 domain of MHC Class II molecules interacts with the CD4 co-receptor on helper T cells to stabilize the TCR-MHC interaction.
Correct answer is: β2 domain
Q.24 Which cells do NOT express MHC Class I molecules?
Red blood cells
All nucleated cells
Hepatocytes
Neurons
Explanation - Mature red blood cells lack nuclei and therefore do not express MHC Class I molecules.
Correct answer is: Red blood cells
Q.25 MHC Class III genes encode:
Complement proteins and cytokines
Antigen-presenting molecules
T cell receptors
Invariant chain
Explanation - MHC Class III genes encode various immune molecules like complement components (C2, C4) and TNF cytokines, not antigen-presenting molecules.
Correct answer is: Complement proteins and cytokines