中科院细胞与分子免疫学课程课件8.pptVIP

* * * * * * * * * * * * * * * * * * * * * * * * * 上堂课回顾： B淋巴细胞的成熟： 祖B细胞，前B细胞，非成熟B细胞，成熟B细胞 两次选择： 阴性选择：在骨髓中，表达与自身抗原有强亲和力的抗原受体的非成熟的B细胞将无法成为成熟的B淋巴细胞。 阳性选择：与T淋巴细胞的阳性选择不同，有可能，只要能够表达抗原受体识别抗原的B细胞都能够被保留下来。 T淋巴细胞的成熟： 祖T细胞，前T细胞，双阳性阶段，单阳性阶段，成熟阶段 两次选择： 1. 阳性选择： 2. 阴性选择： Chapter 8 Activation of T lymphocytes How to activate the T cell? In peripheral lymphoid organs, Na?ve T lymphocytes recognize antigens and are activated. In lymphoid organs or in nonlymphoid tissues, effector T cells recognize antigens and are activated. The activation of T cells requires a. antigen presented by APC b. costimulators c. cytokines produced by the APCs and by the T cells. 4a. Na?ve T cells require activation by dendritic cells; 4b. Effector T cells can respond to antigens presented by a wider variety of APC. What the activated T cells can do? Proliferation Differentiation into Effector Cells CD4+ T cell: Th1 and Th2 Th1: Stimulate cytokine( IL-12 and IFN-g), secrete cytokines: IL-2, INF-g and TNF-b. Th2: Stimulate cytokine:IL-4, secrete cytokines: IL-4,5,6,10,13. CD8+ T cell differentiate into functional CTL. 3. Differentiation into Memory Cells 4. Decline of T Cell Responses Role of Costimulators in T Cell Activation Costimulators :CD28 : B7-1 and B7-2 The expression of costimulators is regulated to make sure the correct time and place expression The expression of B7 costimulators is increased 2a. by microbial products, 2b. by cytokines of innate immunity 3. Mature dendritic cells express the highest levels of costimulators. 4. Adjuvants are products of microbes that stimulate the expression of costimulators. 5. Previously activated effector and memory T cells are less dependent on costimulation by the B7:CD28 pathway than are na?ve cells. Role of CD40 in T cell activation Activated T cells express CD40L APCs express CD40 CD40L binding to CD40 can deliver signals that enhance the expression of B7 costimulators on the APCs. Secretion of cytokines IL-12 is inc