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T细胞接受来自抗原提呈细胞阴性的或阳性的共刺激信号。在na(?)ve T细胞活化的过程中,CD28受体介导活化的共刺激信号,而CTLA-4则介导活化的抑制性信号。CD28和CTLA-4与表达在APCs表面的相同的配体即B7-1和B7-2相结合。另外的CD28-B7家族成员也已经被鉴定,第二个T细胞表面的活化性受体是可诱导的共刺激因子(ICOS),及表达在淋巴和非淋巴细胞表面的它的配体B7H(或称为B7RP-1,GLS0,B7H2,LICOS)。第二个抑制性受体PD-1,与B7相关的配体PD-L1相结合。另一个B7的同系物B7-H3,与活化的T细胞表面的另一个未知受体相结合。
T cells receive co-stimulatory signals from antigen-presenting cells that are negative or positive. CD28 receptors mediate activated co-stimulatory signals during na [?) Ve T cell activation, whereas CTLA-4 mediates activation of inhibitory signaling. CD28 and CTLA-4 bind to the same ligands expressed on the surface of APCs, B7-1 and B7-2. Additional members of the CD28-B7 family have also been identified. The second activated T cell surface receptor is an inducible co-stimulatory factor (ICOS) and its ligand, B7H, expressed on the surface of both lymphoid and non-lymphoid cells Or B7RP-1, GLS0, B7H2, LICOS). The second inhibitory receptor, PD-1, binds to B7-associated ligand, PD-L1. Another B7 homolog, B7-H3, binds to another unknown receptor on the surface of activated T cells.