Abstract: Objective To investigate the regulation of cell proliferation and apoptosis in psoriasis.Methods The expressions of Bcl-X, Bcl-2 and Bax were studied with immunohistochemical technique(SP) in the lesional and non-lesional psoriatic skin.Results There were significant overexpressions of Bcl-X in all layers of epidermis, inflammatory cells and vascular endothelia in dermis; there were mild up-regulations of Bax expression in stratum granulosum and stratum spinosum in the lesional skin.Those abnormalities had already been observed in part of non-lesional skin and not returned to normal afer treatment.However, the expression of Bcl-2was as normal, restricted only to melanocytes in the basal layer; and no Bcl-2 expression was found in keratinocytes.Conclusion The up-regulated ratio of Bcl-X to Bax probably contributes to the overproliferation of keratinocytes, intensive infiltration of inflammatory cells and hyperplasia of new vessels.Bcl-2 may be less important for the initiation of psoriasis.

Key words: Psoriasis, Apoptosis, Bcl-X, Bcl-2, Bax