It describes the structure and functions of MHC antigens and presenting the antigens by APC cells.

1. STRUCTURE & FUNCTIONS OF MHC
Mr. A. T. Sharma
Assist. Professor
Nanded Pharmacy College, Nanded

2. MHC Antigens
• A set of cell surface proteins in all human beings and vertebrates
called Major Histocompatibility Complex antigens
• Essential for acquired immune system to identify foreign molecules.
• Bind to antigens of pathogens and display (present) them on the
cell surface for identification by T-cells
• MHC is a tightly linked cluster of genes present on chromosome 6
in humans and chromosome 17 in mouse which encodes MHC
antigens
• Discovered from antigenic differences in WBCs of different
individuals, so called as Human Leukocyte Antigens (HLA), (in
mouse, H-2 genes)
• George Snell from USA (1950) – concept of MHC participation in
transplant rejection (Nobel Prize in 1980)
• Only identical twins have exactly same MHC molecules
• Matched during organ transplantation – tissue typing (HLA-DR
antigens matched)
• Susceptibility to autoimmune disorder

3. Classes:
Class I:
• They secrete glycoproteins, called Class-I MHC molecule
• Expressed on the surface of all nucleated cells (Antigen
presenting cells)
• Present the peptide antigens to TC cells
• Have β2 subunits - recognized only by CD8 co-receptors on
TC cells
Class II:
• They secrete glycoproteins, called Class-II MHC molecule
• Expressed on the surface of macrophages, dendritic cells,
epithelium of thymus, some endothelial cells and B-cells
(Antigen presenting cells)
• Present the peptide antigens to TH cells
• Have β1 and β2 subunits - recognized only by CD4 co-
receptors on TH cells

4. Class III:
• They consists of complement components C4,
C2, Factor B, inflammatory cytokines including
TNF, heat shock proteins (Play a role in
immune function)
• Located between Class I and Class II genes

5. APC Cells with MHC

6. Structure of Class I and Class II MHC

7. Functions of MHC
• Act as antigen presenting structure – role in
cell mediated and humoral immune response
• Play a role in development of autoimmune
diseases
• Tissue typing during organ transplantation
• In graft versus host response
• Class III MHC play a role in immunity through
complement system and in inflammatory
response.

8. Thank You…!!!