1、vT 细胞亚群vT 细胞活化机制vT 细胞免疫应答及其效应Phases of T cell responsesprimingv T cell subsetsq T cells (95%) and T cells (5%) q CD4+T cells and CD8+T cellsq Nave T cells（初始 T细胞）Effector T cells （效应 T细胞）Memory T cells （记忆 T细胞）q T helper (Th) 辅助性 CD4+T细胞Cytotoxic T cells (CTLs) 细胞毒性 CD8+T细胞Regulatory T cells (Tregs)
2、 调节性 CD4+T细胞T Cell subsetsClass Functions Antigen receptor and specificitySelected markersPercent of total lymphocytes (human) T lymphocytesBlood Lymph nodeSpleenCD4+ helper T lymphocytesB cell differentiation (humoral immunity)Macrophage activation (cell-mediated immunity) heterodimersDiverse speci
3、ficities for peptide-class II MHC complexesCD3+, CD4+, CD8- 50-60* 50-60 50-60CD8+ cytotoxic T lymphocytesKilling of cell infected with microbes, killing of tumor cells heterodimersDiverse specificities for peptide-class I MHC complexesCD3+, CD4-, CD8+ 20-25 15-20 10-15Regulatory T cellsSuppress fun
4、ction of other T cells (regulation of immune responses, maintenance of self-tolerance) heterodimers CD3+, CD4+, CD25+ (Most common, but other phenotypes as well)Rare 10 10 T lymphocytesHelper and cytotoxic functions (innate immunity) heterodimersLimited specificities for peptide and nonpeptide antig
5、ensCD3+, CD4, and CD8 variablePositive selectionNegative selectionT cell development in the thymusPhases of T cell responsesprimingq Nave T cells Mature T cells that have not previously encountered antigen; Preferential migration to secondary lymphoid organs (lymph nodes), where they recognize antig
6、enq Effector T cells Activated T cells capable of performing the functions required to eliminate foreign antigens Preferential migration to sites of infection or inflammation Short-livedq Memory T cells Long-lived, functionally silent cells; Mount rapid secondary immune responses to the same antigen exposure Heterogenous (central and effector)Based on the history of antigen encounter and the stage of T cell activation.
