MHC Structure and Function

Question 1

What is the major histocompatibility complex MHC?

Answer 1

A group of molecules that present antigens to T cells for immune recognition

Question 2

What is the function of MHC molecules?

Answer 2

To bind peptide antigens and present them to T cells for activation

Question 3

What cells express MHC Class II molecules?

Answer 3

Antigen-presenting cells such as dendritic cells macrophages and B cells

Question 4

What antigens do MHC Class I molecules present?

Answer 4

Endogenous antigens derived from within the cell such as viral proteins

Question 5

What antigens do MHC Class II molecules present?

Answer 5

Exogenous antigens that are processed after being taken up by antigen-presenting cells

Question 6

What is the peptide-binding pocket of MHC molecules?

Answer 6

The region on MHC molecules where antigenic peptides are bound and presented to T cells

Question 7

What is HLA?

Answer 7

Human leukocyte antigen - genes in the MHC molecules that help code for proteins that differentiate between self and non self molecules.

Question 8

Where are HLA genes located?

Answer 8

On the short arm of chromosome 6 at position 6p21.3

Question 9

What is the role of HLA polymorphism?

Answer 9

It allows MHC molecules to bind and present a diverse range of peptides to T cells

Question 10

What are the classical HLA Class I genes?

Answer 10

HLA-A HLA-B and HLA-C

Question 11

What are the classical HLA Class II genes?

Answer 11

HLA-DP HLA-DQ and HLA-DR

Question 12

What is MHC restriction?

Answer 12

The concept that T cells recognize antigens only when presented by self-MHC molecules

Question 13

How is MHC diversity generated?

Answer 13

Through polygeny - the presence of multiple HLA genes and polymorphism / the existence of multiple alleles for each gene

Question 14

What is the significance of MHC diversity?

Answer 14

It helps populations combat a wide range of pathogens and prevents immune evasion by rapidly mutating pathogens

Question 15

What are the two models of T cell recognition of MHC molecules?

Answer 15

The dual recognition model and the altered self model

Question 16

What is the dual recognition model of MHC recognition?

Answer 16

It proposes that T cells have two receptors one for the MHC molecule and one for the antigen

Question 17

What is the altered self model of MHC recognition?

Answer 17

It proposes that T cells recognize a single receptor that identifies the MHC molecule modified by the antigen

Question 18

What is the role of MHC in transplant rejection?

Answer 18

Differences in HLA alleles between donor and recipient can trigger immune responses leading to graft rejection

Question 19

What is the peptide length preference for MHC Class I molecules?

Answer 19

Peptides of 8 to 10 amino acids in length

Question 20

What is the peptide length preference for MHC Class II molecules?

Answer 20

Peptides of 13 to 25 amino acids in length

Question 21

What is the role of beta-2 microglobulin in MHC Class I molecules?

Answer 21

It stabilizes the structure of MHC Class I and helps in presenting peptides to T cells

Question 22

What is the effect of HLA polymorphism on disease susceptibility?

Answer 22

Certain HLA alleles are associated with increased or decreased susceptibility to autoimmune diseases and infections

Question 23

What is the importance of MHC in the adaptive immune response?

Answer 23

MHC molecules present antigens to T cells enabling the activation of the adaptive immune system

Question 24

What is the role of HLA in viral infections?

Answer 24

HLA molecules present viral peptides to T cells allowing the immune system to recognize and target infected cells

Question 25

How does MHC diversity protect populations from pathogens?

Answer 25

By increasing the range of peptides that can be presented it reduces the likelihood of pathogens evading immune detection