Abstract: Objective To investigate the pathogenesis of psoriasis induced by staphylococcal superantigen. Methods The proliferation responses of keratinocyte s were measured by ³H-TdR incorporation assay. Quantification of hypodiploid c ells, analysis of DNA fragmentation, and annexin V method were employed to detec t cell apoptosis. The expression of surface antigens on keratinocytes was determ ined by flow cytometric assay. Results The supernatants of peripheral blood lymp hocytes stimulated by staphylococcal enterotoxins B(SEB) could promote the proli feration of keratinocytes and induce the expression of HLA-DR and Fas antigens on keratinocytes after the first 48 h of treatment. Apoptosis of keratinocytes was induced after addition of the same supernatants(P<0.01) for another 48 h. Conclusions Cytokines released by T lymphocytes activated by SEB, a staphyloco ccal superantigen, may firstly stimulate the proliferation, and then induce apop tosis of kera tinocytes.

Key words: Psoriasis, Superantigens, Keratinocytes, Apoptosis, Staphylococcus,aureus