Major HistocoMpatibility coMplex (MHc)
Definitions:-
➢ MHC is a genetic region encoding proteins involved in immune system recognition.
➢ MHC molecules present antigens to T cells, aiding in distinguishing between self and non-self.
➢ Crucial for defense against pathogens and abnormal cells.
➢ MHC serves as "identification tags" on cell surfaces for immune re cognition.
MHc class i:-
➢ Consists of a single polypeptide chain (α chain) associated with β2-
microglobulin.
➢ The α chain has three extracellular domains: α1, α2, and α3.
➢ β2-microglobulin stabilizes the structure of the MHC class I molecule.
types: -
HLA-A:
➢ Encodes alleles for the α chain of MHC class I molecules.
HLA-B:
➢ Also encodes alleles for the α chain of MHC class I molecules.
HLA-C:
➢ Another set of alleles encoding the α chain of MHC class I molecules.
function: -
➢ Initiates immune responses against infected or abnormal cells.
➢ Interaction between MHC class I molecules presenting foreign antigens and CD8+ T cells
triggers the activation and proliferation of cytotoxic T lymphocytes (CTLs).
➢ CTLs recognize and eliminate the target cells displaying the specific antigen, contributing to
the clearance of infections or abnormal cells.
size:- MHC class I: Consists of a single polypeptide chain (α chain) associated with β2-microglobulin.
MHc class ii:-
➢ Comprises two polypeptide chains, α and β, forming a heterodimer.
➢ Each chain contains two extracellular domains: α1 and α2 for the α chain, and β1 and β2 for
the β chain.
types: -
-1-
, HLA DP:-
➢ Encoded by the HLA-DP gene locus.
➢ Plays a role in presenting antigens to CD4+ T cells.Polymorphic, with multiple allelic
variants contributing to individual differences in immune responses.
➢ Expressed on the surface of antigen-presenting cells (APCs) such as dendritic cells,
macrophages, and B cells.
HLA-DQ (DQ):
➢ Encoded by the HLA-DQ gene locus.
➢ Involved in presenting antigens to CD4+ T cells and regulating immune responses.
➢ Polymorphic, with diverse allelic variants influencing antigen presentation and immune
function.
➢ Expressed primarily on APCs, contributing to the diversity of antigen presentation and
immune recognition.
HLA-DR (DR):
➢ Encoded by the HLA-DR gene locus.Predominantly responsible for presenting antigens
to CD4+ T cells and activating immune responses.
➢ Highly polymorphic, with extensive allelic diversity contributing to individual immune
responsiveness and susceptibility to diseases.
➢ Expressed on professional APCs, including dendritic cells, macrophages, and B cells,
where it plays a crucial role in antigen presentation and immune regulation.
function: -
➢ MHC class II molecules present exogenous antigens (from outside the cell) to CD4+ helper T cells.
➢ These antigens are typically derived from extracellular pathogens acquired through phagocytosis or
endocytosis.
➢ Interaction between antigen-MHC class II complex and CD4+ T cells initiates immune responses,
including activation of other immune cells and cytokine secretion
size: -MHC class II: Comprises two polypeptide chains (α and β chains) forming a heterodimer.
toll like receptor (tlr)
structure:
➢ TLRs are type I membrane glycoproteins.
➢ Homology in the cytoplasmic region--- interleukin-1 receptors (IL-1Rs) super family.
➢ Extracellular region of TLRS contains leucine-rich repeat (LRR) motifs, & IL 1Rs contains three
immunoglobulin-like domain.
-2-
Definitions:-
➢ MHC is a genetic region encoding proteins involved in immune system recognition.
➢ MHC molecules present antigens to T cells, aiding in distinguishing between self and non-self.
➢ Crucial for defense against pathogens and abnormal cells.
➢ MHC serves as "identification tags" on cell surfaces for immune re cognition.
MHc class i:-
➢ Consists of a single polypeptide chain (α chain) associated with β2-
microglobulin.
➢ The α chain has three extracellular domains: α1, α2, and α3.
➢ β2-microglobulin stabilizes the structure of the MHC class I molecule.
types: -
HLA-A:
➢ Encodes alleles for the α chain of MHC class I molecules.
HLA-B:
➢ Also encodes alleles for the α chain of MHC class I molecules.
HLA-C:
➢ Another set of alleles encoding the α chain of MHC class I molecules.
function: -
➢ Initiates immune responses against infected or abnormal cells.
➢ Interaction between MHC class I molecules presenting foreign antigens and CD8+ T cells
triggers the activation and proliferation of cytotoxic T lymphocytes (CTLs).
➢ CTLs recognize and eliminate the target cells displaying the specific antigen, contributing to
the clearance of infections or abnormal cells.
size:- MHC class I: Consists of a single polypeptide chain (α chain) associated with β2-microglobulin.
MHc class ii:-
➢ Comprises two polypeptide chains, α and β, forming a heterodimer.
➢ Each chain contains two extracellular domains: α1 and α2 for the α chain, and β1 and β2 for
the β chain.
types: -
-1-
, HLA DP:-
➢ Encoded by the HLA-DP gene locus.
➢ Plays a role in presenting antigens to CD4+ T cells.Polymorphic, with multiple allelic
variants contributing to individual differences in immune responses.
➢ Expressed on the surface of antigen-presenting cells (APCs) such as dendritic cells,
macrophages, and B cells.
HLA-DQ (DQ):
➢ Encoded by the HLA-DQ gene locus.
➢ Involved in presenting antigens to CD4+ T cells and regulating immune responses.
➢ Polymorphic, with diverse allelic variants influencing antigen presentation and immune
function.
➢ Expressed primarily on APCs, contributing to the diversity of antigen presentation and
immune recognition.
HLA-DR (DR):
➢ Encoded by the HLA-DR gene locus.Predominantly responsible for presenting antigens
to CD4+ T cells and activating immune responses.
➢ Highly polymorphic, with extensive allelic diversity contributing to individual immune
responsiveness and susceptibility to diseases.
➢ Expressed on professional APCs, including dendritic cells, macrophages, and B cells,
where it plays a crucial role in antigen presentation and immune regulation.
function: -
➢ MHC class II molecules present exogenous antigens (from outside the cell) to CD4+ helper T cells.
➢ These antigens are typically derived from extracellular pathogens acquired through phagocytosis or
endocytosis.
➢ Interaction between antigen-MHC class II complex and CD4+ T cells initiates immune responses,
including activation of other immune cells and cytokine secretion
size: -MHC class II: Comprises two polypeptide chains (α and β chains) forming a heterodimer.
toll like receptor (tlr)
structure:
➢ TLRs are type I membrane glycoproteins.
➢ Homology in the cytoplasmic region--- interleukin-1 receptors (IL-1Rs) super family.
➢ Extracellular region of TLRS contains leucine-rich repeat (LRR) motifs, & IL 1Rs contains three
immunoglobulin-like domain.
-2-
