This set of Immunology Multiple Choice Questions & Answers (MCQs) focuses on “Role of MHC and Expression Patterns”.
1. What does MHC in Immunology stand for?
a) Major Histochemical Complex
b) Minor Histocompatibility Complex
c) Major Histocompatibility Complex
d) Major Histogram Complex
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Explanation: Major Histocompatibility Complex (MHC) is a group of genes that code for proteins, which are found on the cell surface. It is also referred to as a cluster of linked genes. It is polymorphic in nature. MHC plays an important role in recognizing foreign particle/substance. It was first identified in mice strains.
2. Which of the following is NOT the role of MHC?
a) Development of humoral and cell-mediated immune responses
b) Helps in antigen recognition by T-cells
c) Responsible for determining whether transplanted tissue will be compatible or not
d) Has specific killing effects
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Explanation: Cytotoxic T-lymphocytes (CTLs) has specific killing effects. They have the ability to find the cells that carry viral peptide. Once CTLs have found these cells, they induce them to secrete proteins that attract nearby macrophages. These macrophages surround and destroy the infected cells.
3. What is the chemical composition of MHC I molecule?
a) It consists of one α and one β2-microglobulin (B2M) polypeptide chains
b) It consists of two α and one β2- macroglobulin (B2M) polypeptide chains
c) It consists of an α1 and a β1 polypeptide chains
d) It consists of two α1 and one β1 polypeptide chains
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Explanation: MHC class 1 molecules are heterodimers consisting of two polypeptide chains (α and β2-microglobulin {B2M}) These two chains are linked by non-covalent bond between B2M and an α3 domain. The α chain is polymorphic and is encoded by HLA gene while B2M is not polymorphic and it is encoded by Beta-2 microglobulin gene.
4. What is MHC in humans called?
a) Human Lymphocyte Antigen System
b) Human Leukocyte Antigen System
c) Human Leukocyte Antibody System
d) Human Lymphocyte Antibody System
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Explanation: The human MHC is also called as Human Leukocyte Antigen (HLA) system. There are 3 major and 3 minor MHC class 1 gene in HLA, whereas, there are 3 major and 2 minor MHC class 2 proteins encoded by HLA. This HLA system is an important part of the human immune system and it is controlled by the gene located on chromosome 6. It plays an important role in encoding cell surface molecules.
5. Who discovered Major Histocompatibility Complex (MHC) molecule?
a) George Snell
b) William Coley
c) Peter Gorer
d) Jean Dausset
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Explanation: The discovery of MHC was made by Peter Gorer, British Immunologist in 1936. MHC genes were first identified in mice strains. Further researches on MHC were done by other scientists like Clarence Little, George Snell and Baruj Benacerraf. The first fully sequenced and annotated MHC was published for humans in 1999.
6. Which of the following ways is NOT mediated by MHC antigens in order to showcase diversity of antigen presentation?
a) Via multiple interacting genes
b) Via both sets of inherited alleles
c) By variations from organism to organism within a species
d) By expression of same allele within same species
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Explanation: MHC is polygenic in nature and its expression is codominant. MHC genes are also polymorphic in nature therefore they vary from organism to organism. As a result, expression of same allele within same species is not possible and it is against the nature of MHC gene. Sexual selection has been observed in male mice mating with female mice having different MHCs. It has been observed that, for MHC I presentation, antigenic peptide splicing takes place resulting in binding to peptides of different proteins thereby increasing the antigenic diversity.
7. What is the origin of antigenic proteins in MHC 1 Pathway?
a) Cytosolic Proteins
b) Proteins in Endosomes and Lysosomes
c) Proteins from Endoplasmic Reticulum
d) Integral Proteins
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Explanation: Cytosolic proteins are mostly synthesized by the cell for their involvement. They may also enter from the extracellular medium via phagosomes. Cytosolic Proteasome enzyme is responsible for the degradation of these cytosolic proteins to give rise to cytosolic peptides which are further transferred to endoplasmic reticulum via TAP (Transport Associated with antigen Processing) Channel.
8. All individuals of same species express same allele of MHC genes. True or False?
a) True
b) False
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Explanation: MHC genes are polymorphic in nature which means that they have the ability to be expressed in several different forms of alleles. Due to polymorphism, there are many different alleles in different individuals in same species. As a result, MHC molecules have a broad specificity.
9. In humans, which of the following types of Transplant Rejection is NOT mediated by MHC (HLA)?
a) Hyperacute Rejection
b) Acute Cellular Rejection
c) Acute Humoral Rejection and Chronic Disfunction
d) Acute Antibody Mediated Rejection
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Explanation: Acute Antibody Mediated Rejection (AMR) is NOT mediated by MHC (HLA). It occurs due to donor-specific antihuman leukocyte antigen antibodies. These antibodies activate the complement system and may develop before or after transplantation. On the other hand, Hyperacute Rejection occurs before or few minutes after transplantation whereas Acute Cellular Rejection occurs when recipient’s T-lymphocytes are activated by the donor tissue. Chronic rejection can occur over many years.
10. Which of the following proteins is not a type of MHC class II?
a) HLA-DP
b) HLA-DQ
c) HLA-DR
d) HLA-B
View Answer
Explanation: HLA-B is a type of major MHC class I proteins. MHC class I consists of 3 major (HLA-A, HLA-B, HLA-C) and 3 minor (HLA-E, HLA-F, HLA-G) proteins whereas MHC II proteins include 3 major (HLA-DP, HLA-DQ & HLA-DR) and 2 minor (DM & DO) proteins.
Sanfoundry Global Education & Learning Series – Immunology.
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