Major Histocompatibility Major Histocompatibility complexcomplex

OROR

MHCMHC

MHCMHC

The principal function of T cells are :The principal function of T cells are :Defense against intracellular microbesDefense against intracellular microbesActivation of other cells(B cells ,Macrophages )Activation of other cells(B cells ,Macrophages )

peptide recognition by T and B cells peptide recognition by T and B cells is different.is different.

B cells recognize soluble as well as cell associated AgsB cells recognize soluble as well as cell associated AgsIn contrast ,T cells recognize peptide which is displaying only In contrast ,T cells recognize peptide which is displaying only

by APC in associated with MHC proteins.by APC in associated with MHC proteins.

MHCMHC MHC genes are the most polymorphic genesMHC genes are the most polymorphic genes MHC genes are codominantly expressed in MHC genes are codominantly expressed in

each individualeach individual There are two main type of MHC:class I & IIThere are two main type of MHC:class I & II The physiologic function of MHC molecules The physiologic function of MHC molecules

is presentation of peptides to T cells ,control is presentation of peptides to T cells ,control of immune responsiveness to all proteins of immune responsiveness to all proteins and graft rejectionand graft rejection

MHC-I present cytosolic peptides to T MHC-I present cytosolic peptides to T cytotoxic cells and MHC-II present cytotoxic cells and MHC-II present endocytosed peptides to Thendocytosed peptides to Th cellscells

MHC genesMHC genes

MHC –I structureMHC –I structure

MHC-II structureMHC-II structure

T cell receptor and MHC T cell receptor and MHC interactioninteraction

Polymorphism of class IIPolymorphism of class II

HLA-DPA 12HLA-DPA 12 HLA-DPB 88HLA-DPB 88 HLA-DQA 17HLA-DQA 17 HLA-DQB 42HLA-DQB 42 HLA-DR >400HLA-DR >400

Polymorphism of class IPolymorphism of class I

HLA-A >280HLA-A >280 HLA-B >500HLA-B >500 HLA-C >130HLA-C >130

MHC genes and graft rejectionMHC genes and graft rejection

HLA expressionHLA expression

Peptide presentation by MHC-IIPeptide presentation by MHC-II

Peptide presentation by MHC-IPeptide presentation by MHC-I