Study Of Superantigen And Immune Tolerance

SAgs are proteins operationally defined as bifunctional molecules that bind to MHC class II strucrures and activate T cells expressing appropriate Vp segments of the T-cell receptor. The proliferation, selective deletion and anergy of T cell ensue after challenge with superantigens. superantigens have been used as a model for the study of peripheral T cell and have became especially important to study tolerance of T cell in vivo. TO study the mechanism of peripheral T cell tolerance induced by superantigen staphylococus aureus enterotoxin B (SAgSEB). Spleen cells from C57BL/6J (B6) mice were stimulated by SEB in vitro. The lymphocytes were stained with MTT. OD value was measured as proliferating parameter. The percentage of B cells and T cell population, S and G0-G1 phase peak and MHC-I H-2Kb expression of T cell were analyzed by flow cytometry (FCM). The T cells anergy was detected by second antigen stimulayion. Apoptosis of anergic T cell was observed with FCM , DNA electrophoresis ladder and optic microscope. The results showed that SEB could induce strong proliferation on CD4+T cell and the highest percentage of CD4+T cell in S phase appeared on 3th day after SEB stimulation and then decreased, but the percentage of CD4+T cell in G0-G1 phase was opposite. CD4+T cell became anergy on 3rd day and apoptosis of anergic CD4+T cell appeared on 5th day. Percentage of apoptosis cell increased gradually and could not be reversed by addition of anti CD3 Ab and ConA. Expression of MHC-I H-2Kh was marginally declined accompanied by CD4+T cell anergy afterSEB exposure.These results suggest that ability of proliferation of CD4+T cell gradually decrease which restrain the response to the second stimulation and is in anergic state. The development of T cell anergy is not because of apoptosis and the apoptosis is neither dependent on the depletion of essential nutrients nor on the build-up of toxic metabolites in culture medium. Decline of MHO-I molecular play an important role in SAg SEB-induced T cell anergy . SEB-induced tolerance might be related with anergy of CD4+ T cell , apoptosis and downregulation of MHC-I molecular.