CTLA-4, a second T cell receptor for B7, which is expressed on the surface ofactivated T cells, has been shown to play an inhibitory role in regulation of T cellresponses by preventing full T cell activation or terminating T cell responses.

• 细胞毒性T淋巴细胞相关抗原4（cytotoxic T lymphocyte associated antigen 4，CTLA-4），是共刺激分子B7的受体，主要表达于激活的T细胞表面，与B7结合后能抑制小鼠和人的T细胞的激活，在T细胞活化中起负调节作用。