MHC Structure and Function Flashcards
What is the major histocompatibility complex MHC?
A group of molecules that present antigens to T cells for immune recognition
What is the function of MHC molecules?
To bind peptide antigens and present them to T cells for activation
What cells express MHC Class II molecules?
Antigen-presenting cells such as dendritic cells macrophages and B cells
What antigens do MHC Class I molecules present?
Endogenous antigens derived from within the cell such as viral proteins
What antigens do MHC Class II molecules present?
Exogenous antigens that are processed after being taken up by antigen-presenting cells
What is the peptide-binding pocket of MHC molecules?
The region on MHC molecules where antigenic peptides are bound and presented to T cells
What is HLA?
Human leukocyte antigen - genes in the MHC molecules that help code for proteins that differentiate between self and non self molecules.
Where are HLA genes located?
On the short arm of chromosome 6 at position 6p21.3
What is the role of HLA polymorphism?
It allows MHC molecules to bind and present a diverse range of peptides to T cells
What are the classical HLA Class I genes?
HLA-A HLA-B and HLA-C
What are the classical HLA Class II genes?
HLA-DP HLA-DQ and HLA-DR
What is MHC restriction?
The concept that T cells recognize antigens only when presented by self-MHC molecules
How is MHC diversity generated?
Through polygeny - the presence of multiple HLA genes and polymorphism / the existence of multiple alleles for each gene
What is the significance of MHC diversity?
It helps populations combat a wide range of pathogens and prevents immune evasion by rapidly mutating pathogens
What are the two models of T cell recognition of MHC molecules?
The dual recognition model and the altered self model
What is the dual recognition model of MHC recognition?
It proposes that T cells have two receptors one for the MHC molecule and one for the antigen
What is the altered self model of MHC recognition?
It proposes that T cells recognize a single receptor that identifies the MHC molecule modified by the antigen
What is the role of MHC in transplant rejection?
Differences in HLA alleles between donor and recipient can trigger immune responses leading to graft rejection
What is the peptide length preference for MHC Class I molecules?
Peptides of 8 to 10 amino acids in length
What is the peptide length preference for MHC Class II molecules?
Peptides of 13 to 25 amino acids in length
What is the role of beta-2 microglobulin in MHC Class I molecules?
It stabilizes the structure of MHC Class I and helps in presenting peptides to T cells
What is the effect of HLA polymorphism on disease susceptibility?
Certain HLA alleles are associated with increased or decreased susceptibility to autoimmune diseases and infections
What is the importance of MHC in the adaptive immune response?
MHC molecules present antigens to T cells enabling the activation of the adaptive immune system
What is the role of HLA in viral infections?
HLA molecules present viral peptides to T cells allowing the immune system to recognize and target infected cells
How does MHC diversity protect populations from pathogens?
By increasing the range of peptides that can be presented it reduces the likelihood of pathogens evading immune detection
