[Anergy, apoptosis and decreased MHC class I molecule expression of C57BL/6J mouse CD4+ T cells induced by SEB]

To study the mechanism of peripheral T cell tolerance induced by superantigen Staphylococus aureus enterotoxin B (SAgSEB).

Splenocytes from C57BL/6J (B6) mice were stimulated with SEB in-vitro. The proliferation of lymphocytes was determined by MTT colorimetry. The apoptosis of anergic T cells, the cells being in the S and G(0)-G(1) phase and MHC-I (H-2K(b)) expression of T cells were analyzed by flow cytometry (FCM). Apoptosis of anergic T cells was also demonstrated by DNA electrophoresis ladder.

SEB could induce strong proliferation of CD4+ T cells and the maximal percentage of CD4+ T cells in S phase appeared on 3rd day after SEB stimulation and then decreased, but the changes of percentage of CD4+ T cells in G(0)-G(1) phase was opposite to that in S phase. CD4+ T cells became anergy on 3rd day and apoptosis of anergic CD4+ T cells appeared on 5th day. Percentage of apoptosis cells increased gradually and could not be reversed by addition of anti-CD3 Ab and ConA. Expression of MHC-I (H-2K(b)) was marginally declined accompanied by CD4+ T cell anergy after SEB exposure.

SEB-induced tolerance may have relation to anergy and apoptosis of CD4+ T cells, and down-regulation of MHC-I molecules.