The major histocompatibility complex (MHC) is a set of surface proteins located on nucleated cells that plays an important role in distinguishing self from non-self and antigen presentation. There are two types of MHC molecules: class I MHC molecules present antigens to cytotoxic T cells on all nucleated cells, while class II MHC molecules present antigens to helper T cells and are found only on antigen-presenting cells. Both MHC classes consist of a transmembrane alpha chain and beta chain that form a peptide-binding groove to load and present antigen peptides. MHC molecules allow the immune system to recognize foreign substances so the body's immune response can be triggered.

1. MAJOR HISTOCOMPATIBILITY COMPLEX
(MHC)
By; Omer ASLANKAN

2. INTRODUCTİON
• Major Histocompactibility complex (MHC) is set of
surface proteins located on the cell membrane of
nucleated cells.
• It plays more important work to indentify the antigen
between self and non self body, intracellular
recognization and responsible for antigen presentation.
• Histo refers to tissues. Compatibility refers to living
together harmoniously.
• MHC molecules always recognize only T lymphocytes.
• The two types of MHC are worked in immunity.
• T helper (Th) cell recognized by MHC molecules II.
• T cytotoxic (Tc) cells are recognized by MHC I
molecules.

3. ANTIGEN-PRESENTING CELLS

4. CLASS I MHC MOLECULES
• Class I MHC molecule are a group of major histocompactibility
antigen.
• They are present on the surface of all nucleated cells except
nervous tissue and platelets.
• It present antigen to Tc cells.
• It bind with CD-8 adhesion molecules of Te cells.
• It brings about cell mediated immune response.
• It found on all nucleated cells.

5. STRUCTURE OF CLASS I MHC MOLECULE
• It consists two polypeptide chains namely a chain and B2 - micro globulin.
• a chain which is non covalently attached with B2 microglobuline .
• a chain contain a transmembrane glycoprotein which is encoded by A,B and C gene of
grouped HLA. (Human leukocyte antigens (HLA; are proteins—or markers—on most cells in body)
• a chain is organized by three domains such as a 1, a 2 and a 3 each domain containing
90 amino acids sequences .
• B2 microglobuline is similar in size of a 3 and it dose not contain trans membrane
proteins .
• When the antigen is internalized and processed inside by proteosome (Ubiquitin,
cytosolic degradation), the peptides are produced .
• Peptide is further loaded on the groove of MHC I molecules from endoplasmicreticulum.

6. CLASS II MHC MOLECULE
• Class II MHC molecule are present on the surface of antigen
presenting cell and cell which engulfed the foreign antigen.
• It binds with the exogenous(endocytic degradation ) antigens.
• It binds with CD4 adhesion molecules Th cells.
• It also consist of two polypeptide chains namely a chain and B
chain.
• Antigen is processed inside the endosome and peptide is further
loaded on groove of MHC II molecules.
• It found only on APCs

7. STRUCTURE OF MHC II MOLECULE
• The class II MHC Molecule consists of two polypeptide chain
namely a chain and B chain.
• The both chain are attached noncovelantly.
• Each chain contains two units.
• The two units of a chain are called al and a2.
• The two domains of B chains are called B1 and B2.
• B2 and a2 are transmembrane domains anchoring the MHC to
plasma membrane.
• The al and B1 domains jointly bear a peptide binding groove.

8. MHC ASSOCIATED GENES

9. FUNCTION OF MHC MOLECULES
• MHC molecules are loaded with a bit of sample peptide fragment
derived from the degradation of proteins present inside the cell. This
peptide is the mirror image of proteins present inside the cell.
• MHC molecules contain self as well as nonself (foreign) antigen.
• They bring about defense against infections and diseases.
• They mediate certain autoimmune diseases.
• They are responsible for individual smell of people.

10. DIFFERENCES BETWEEN MHC CLASS I & CLASS II

11. SIMILARITIES BETWEEN MHC CLASS I & MHC CLASS II

12. REFERENCES
• https://www.ncbi.nlm.nih.gov/books/NBK546662/#:~:text=Human%
20leukocyte%20antigens%20(HLA)%20are,can%20also%20have%20
detrimental%20effects.
• https://youtu.be/t81EjpkCiss
• https://quizlet.com/3489839/mhc-i-and-ii-flash-cards/
• https://www.slideshare.net/Prasannjeetsaha/major-histocompatibility-
complex-78885656
• https://www.slideshare.net/AbhijitDebnath143/structure-and-function-
of-mhc