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Major Histocompatibility Complex (MHC)

Major Histocompatibility Complex (MHC). What is MHC? HLA H-2 Minor histocompatibility antigens. Significance of the MHC. role in immune response role in organ transplantation role in predisposition to disease. Genetic barriers to transplantation.

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Major Histocompatibility Complex (MHC)

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  1. Major Histocompatibility Complex(MHC) • What is MHC? • HLA • H-2 • Minor histocompatibility antigens

  2. Significance of the MHC • role in immune response • role in organ transplantation • role in predisposition to disease

  3. Genetic barriers to transplantation • autologous: in the same individual (autograft) • isologous: between genetically Identical individuals (isograft), i.e., identical twins (inbred animals) • homologous: between individuals of the same species (allograft) • heterologous: between individuals different species (xenograft)

  4. Principles of transplantation

  5. Minor histocompatibility antigensand graft survival • minor histocompatibility antigens also cause rejection • The rejection time is variable but longer than that for major histocompatibility antigen • They have additive effects

  6. Graft versus host (GVH) disease

  7. GVH disease in humans

  8. The human MHC genes

  9. The mouse MHC genes

  10. Polymorphism of MHC antigens (based on phenotype)

  11. Polymorphism of MHC genes(based on DNA sequence/ PCR)

  12. The inheritance of MHC genes

  13. MHC products expressed on cells

  14. Crossing overresults in new haplotypes

  15. MHC products expressed on cells If Jack and Jill have four children; Bo, Kim, Mo and Lee They’ll all inherit antigens of the parental MHC Oft their haplotypes will be of the father or mother Unless during meiosis, a crossover should occur

  16. Differential expression of MHC antigens • Class-I expressed on all nucleated cells in man, and also on erythrocytes in mice. • Class-II expressed primarily on antigen presenting cells (dendritic cells, macrophages and B cells, etc.)

  17. CD4+TH1 CD8+preCTL CD8+CTL Alloreactivity of T cells: MLR and CTL generation

  18. Alloreactivity of T cells Alloreaction (MLR) Thymus Positive Selection Proliferation and Differentiation

  19. TNF, NO2 IL2, TNF, IFN  IL2, IL4, IL5 lysis IL2, IFN  Mechanisms of graft rejection Inflammation ADCC lysis rejection

  20. type of rejection cause time taken minutes- hours preformed anti-donor antibodies and complement hyperacute reactivation of sensitized T cells (secondary response) days accelerated primary activation of T cells acute days-weeks unclear causes: cross reactive Ab, immune complexes, slow cellular reaction, tolerance breakdown, disease recurrence months-years chronic Tempo of rejection reaction

  21. A, B & DR matching and graft survival

  22. Blood transfusion and graft survival

  23. agent mode of action application(s) organ transplant, hypersensitivity, autoimmunity organ transplant, corticosteroids, prednisone cyclosporine, ticrolimus anti-inflammatory, altering T-cell and PMN traffic inhibition of IL-2 production by T cells Inhibition of T cell activation by IL-2 organ transplant rapamycin Immunosuppressive agents

  24. agent mode of action application(s) purine metabolism organ transplant azathioprine, 6-MP organ transplant methotrexate folate metabolism autoimmune diseases, organ transplant cyclophosphamide, melphalan alkylation of DNA, RNA and proteins x-irradiation Lymphopenia malignancy/marrow transplantation Immunosuppressive agents

  25. Magnet Removal of T cells from marrow graft Magnetic antibodies

  26. HLA and disease association

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