MHC (Major Histocompatibility Complex)

Question 1

MHC (Major Histocompatibility Complex):

Answer 1

A group of genes encoding cell surface proteins responsible for presenting antigens to T cells, playing a key role in immune recognition.

Question 2

MHC Class I:

Answer 2

Molecules present on the surface of all nucleated cells that present endogenous antigens to CD8+ T cells (cytotoxic T cells).

Question 3

MHC Class II:

Answer 3

Molecules found on antigen-presenting cells (APCs) like dendritic cells, macrophages, and B cells, presenting exogenous antigens to CD4+ T cells (helper T cells).

Question 4

Antigen presentation:

Answer 4

The process by which MHC molecules display fragments of antigens on the cell surface for recognition by T cells.

Question 5

Endogenous antigens:

Answer 5

Antigens that originate from within the cell, such as viral proteins or mutated proteins in cancer cells, presented by MHC Class I.

Question 6

Exogenous antigens:

Answer 6

Antigens that come from outside the cell, such as bacterial proteins, presented by MHC Class II.

Question 7

CD8+ T cells:

Answer 7

Cytotoxic T cells that recognize antigens presented by MHC Class I molecules and kill infected or abnormal cells.

Question 8

CD4+ T cells:

Answer 8

Helper T cells that recognize antigens presented by MHC Class II molecules and activate other immune cells, including B cells and cytotoxic T cells.

Question 9

Peptide binding groove:

Answer 9

The region of the MHC molecule where the antigenic peptide is held for presentation to T cells.

Question 10

T-cell receptor (TCR):

Answer 10

A receptor on T cells that recognizes and binds to the peptide-MHC complex, initiating an immune response.

Question 11

Polymorphism in MHC:

Answer 11

MHC genes are highly polymorphic, meaning there are many variants in the population, which helps the immune system recognize a wide variety of pathogens.

Question 12

MHC I structure:

Answer 12

Composed of a heavy α-chain and β2-microglobulin, with a peptide-binding groove that holds endogenous antigen peptides for presentation.

Question 13

MHC II structure:

Answer 13

Composed of two chains (α and β) that form a peptide-binding groove for exogenous antigen peptides, presenting them to CD4+ T cells.

Question 14

Cross-presentation:

Answer 14

A process where dendritic cells present exogenous antigens via MHC Class I, enabling activation of CD8+ T cells, important for viral and tumor immunity.

Question 15

Antigen processing:

Answer 15

The process by which antigens are degraded into peptides and loaded onto MHC molecules for presentation to T cells.

Question 16

Proteasome in MHC Class I pathway:

Answer 16

A cellular complex that degrades proteins into peptides, which are then transported into the ER and loaded onto MHC Class I molecules.

Question 17

Endosomal/lysosomal pathway for MHC Class II:

Answer 17

The pathway where exogenous antigens are processed in endosomes/lysosomes and then loaded onto MHC Class II molecules.

Question 18

MHC restriction:

Answer 18

The requirement that T cells only recognize antigenic peptides when they are presented by the appropriate MHC molecule.

Question 19

MHC and transplantation:

Answer 19

MHC molecules are key in organ transplantation because mismatched MHC molecules between donor and recipient can lead to graft rejection.

Question 20

MHC polymorphism and immune response:

Answer 20

The diversity of MHC molecules within a population allows for a broader immune response, improving the ability to combat various pathogens.

Question 21

Self vs. non-self recognition by MHC:

Answer 21

MHC molecules help the immune system distinguish between self (normal body cells) and non-self (pathogens or infected cells).

Question 22

MHC and autoimmune diseases:

Answer 22

Faulty MHC recognition or presentation can lead to autoimmune diseases, where the immune system mistakenly attacks the body’s own tissues.

Question 23

MHC Class I deficiency:

Answer 23

A rare condition where mutations in MHC Class I molecules lead to impaired CD8+ T cell responses and increased susceptibility to infections.

Question 24

MHC Class II deficiency:

Answer 24

A genetic disorder where defects in MHC Class II molecules impair CD4+ T cell function, leading to severe immune deficiency.

Question 25

MHC in cancer:

Answer 25

Tumors can evade immune detection by altering the expression of MHC molecules or downregulating antigen presentation.

Question 26

MHC in viral immune evasion:

Answer 26

Some viruses can inhibit MHC Class I antigen presentation, preventing the immune system from detecting and responding to infected cells.

Question 27

MHC-based vaccines:

Answer 27

Vaccines that aim to enhance the presentation of specific antigens via MHC molecules to improve immune responses against diseases like cancer.

Question 28

MHC and disease susceptibility:

Answer 28

Certain MHC variants are associated with increased or decreased susceptibility to various diseases, including infections, autoimmune diseases, and cancer.