The major histocompatibility complex (MHC) is a collection of genes that encode glycoproteins found on the surface of mammalian cells. MHC proteins present antigens and help the immune system distinguish self from nonself. There are two major classes of MHC molecules: class I molecules present antigens to cytotoxic T cells on all nucleated cells, while class II molecules present antigens to helper T cells on antigen-presenting cells that have engulfed foreign antigens. Together, MHC molecules play a key role in cell-cell interaction and initiating adaptive immune responses.

1. Major Histocompatibility Complex
Prepared by: Hawdam Latif Abdulla
Charmo University

2. What Is Major Histocompatibility Complex?
• The major histocompatibility complex (MHC) is a collection of genes that encode
molecules of genetically diverse glycoproteins, that are found on the plasma
membranes of mammalian nucleated cells.
• MHC proteins are found in all higher vertebrates.
• In human beings the complex is also called the human leukocyte antigen (HLA)
system.

3. MHC involved in:
1. cell-cell interaction.
2. Antigen presentation.
3. Recognition of self and nonself molecules.
Two Major Classes Of MHC Molecules
1. Class I MHC molecules
2. Class II MHC molecules

4. Class I MHC Molecules
• They are present on the surface of all nucleated
cells.
• Antigen presentation to cytotoxic T cells.
• It binds with CD8 adhesion molecules of TC
cells.
• It brings about cell mediated immune response.
• Their structure consists two polypeptide chains
namely α chains and β-macroglobulin.

5. @Microbiology - An Introduction 11th Edition
Class I MHC Molecules

6. Class II MHC molecules
• They are present on the surface of antigen
presenting cells (APCs) which engulfed the foreign
antigen.
• Antigen presentation to helper T cells.
• It binds with CD4 adhesion molecules TH cells.
• Their structure consists two polypeptide chains
namely α chain and β chain.

7. @Microbiology - An Introduction 11th Edition
Class II MHC Molecules

8. Reference
Microbiology - An Introduction
11th Edition

9. Any Questions?