Abstract: T lymphocytes are the major effect of the cellular immune response cells. The Central link of the immune response is the recognition of t-cell activation antigen and effective, activate t-cells have double signal mechanism, including TCR with MHC Ag - for the first signal of the complex, APC provides for the second signal collaborative stimulate signal.CD28/ CTLA4 and B7 B7 [B7-1(CD80)，B7-2(CD86)] are currently the most important discovery in collaborative stimulation, they not only have abnormal effect on T cell and the antigen of autoimmunity disease patient,but also participate in pathopoiesia process. After These molecules and their surname combing with the acceptor, in different stages of T cells immune response wich plays an important role in regulating, involving the immune system cells and humoral immune regulation of positive negative aspects. Correct understanding of these pathways for autoimmune diseases will provide a new prospect of treatment.

Key words: B7-CD28/CTLA4, Stimulation of signal, Aplastic anemia