Antigen Processing and Presentation.pptVIP

上海交通大学医学院免疫学教研室 * 抗 原 加 工 提 呈 （Antigen Processing and Presentation） 张 勇 T cells do not recognize native antigens Y Y B Y Y Y Y Y Y Y B Y T Y T Proliferation and antibody production No proliferation Cross-linking of surface membrane Ig Y B Y B Y B Y B Y B Y B Y B Antigens must be processed in order to be recognized by T cells Cell surface peptides of Ag Y T T cell response No T cell response No T cell response No T cell response No T cell response native Ag Cell surface native Ag Soluble peptides of Ag Cell surface peptides of Ag presented by cells that express MHC antigens Ag processing and presentation Since all cells expressing either class I or class II MHC molecules can present peptides to T cells, strictly speaking they all could be designated as Antigen Presenting Cells (APC). However,……………….. Target cells: Cells that display peptides associated with class I MHC molecules to CD8+ Tc cells are referred to as target cells. Professional antigen presenting cells (APC): Cells that display peptides associated with class II MHC molecules to CD4+ Th cells are called APC. APCs: highly specialized cells ? Uptake and process antigens ? Express co-stimulatory molecules ( B7 ) ? Express class II MHC molecules ? Present antigenic peptide to CD4+ T-cell the main APCs are: dendritic cells, macrophages and B cells. The 3 types of APCs Constitutively express a high level of MHC II and the co-stimulatory protein,B7. the most effective APC Constitutively express class II MHC but must be activated to produce B7. must be activated by the process of phagocytosis before expressing class II MHC and B7. 1. dendritic cell (DC) discovered in 1973 Tissue –resident DC surface receptors recognize microbes Immature DC(iDC) migrate to local lymph nodes Within lymph nodes DC present antigens to T cells in MHC molecules mature DC(mDC) iDC mDC Low levels of class II MHC and B7 Strongly internalize antigens but