免疫学前沿06Antigen Processing and resentation 20151210Final.ppt

* * * * * * 内源性抗原的加工与提呈 * * Antigen Presentation APC to T-cell * * * * * These specialized cells, which include macrophages, B lymphocytes, and dendritic cells, are distinguished by two properties: they express class II MHC molecules on their membranes, and (2) they are able to deliver a co-stimulatory signal that is necessary for Th-cell activation. * Class II MHC pathway of presentation of vesicular peptide antigens Helper T cells need to help macrophages and B cells that have encountered (and ingested) microbes Proteins ingested into endosomes/lysosomes (vesicles) are processed and their peptides are presented in association with class II MHC molecules Most vesicular peptides are derived from extracellular proteins that are ingested into vesicles Class II MHC is expressed only on specialized cells (e.g. B cells, macrophages) that are capable of ingesting microbes and antigens into vesicles * Class II MHC pathway of presentation of vesicular peptide antigens Proteins ingested into endosomes/lysosomes are processed and their peptides are presented in association with class II molecules Most vesicular peptides are derived from extracellular proteins that are ingested Class II MHC is expressed only on specialized cells (e.g. B cells, macrophages) that are capable of ingesting microbes and antigens into vesicles CD4 binds to class II MHC; therefore, CD4+ T cells recognize class II-displayed peptides CD4+ T cells are helper cells that activate B lymphocytes and macrophages Antibodies (products of activated B cells) and activated macrophages combat extracellular microbes * Class I MHC pathway of presentation of cytosolic peptide antigens Cytotoxic T lymphocytes need to kill cells containing cytoplasmic microbes, and tumor cells (which contain tumor antigens in the cytoplasm) Cytosolic proteins are processed into peptides that are presented in association with class I molecules Most cytosolic peptides are derived from endogenously synthesized (e.g. viral, tumor) pro