1. بنام خداي زيبائيها

2. Major Histocompatibility complexOR MHC

3. MHC • The principal function of T cells are : Defense against intracellular microbes Activation of other cells(B cells ,Macrophages ) • peptide recognition by T and B cells is different. B cells recognize soluble as well as cell associated Ags In contrast ,T cells recognize peptide which is displaying only by APC in associated with MHC proteins.

4. MHC • MHC genes are the most polymorphic genes • MHC genes are codominantly expressed in each individual • There are two main type of MHC:class I & II • The physiologic function of MHC molecules is presentation of peptides to T cells ,control of immune responsiveness to all proteins and graft rejection • MHC-I present cytosolic peptides to T cytotoxic cells and MHC-II present endocytosed peptides to Thcells

5. MHC genes

7. MHC –I structure

8. MHC-II structure

9. T cell receptor and MHC interaction

11. Polymorphism of class II • HLA-DPA 12 • HLA-DPB 88 • HLA-DQA 17 • HLA-DQB 42 • HLA-DR >400

12. Polymorphism of class I • HLA-A >280 • HLA-B >500 • HLA-C >130

13. MHC genes and graft rejection

14. HLA expression

15. Peptide presentation by MHC-II

16. Peptide presentation by MHC-I