Abstract: Objective To study the relationship between Fas,FasL and apoptosis and their roles in the pathogenesis of psoriasis. Methods Immunohistochemical techniques were employed to study the expression of Fas,FasL in the uninvolved skin, progressive plaque lesions and regressive lesions. Apoptosis was detected with terminal deoxynucleotidyl transferase mediated dUTP DIG nick end labeling (TUNEL). Results ①Both Fas and FasL were expressed on the keratinocytes with basically the same distribution. There were obvious apoptosis of keratinocytes but reduced infiltration of mononuclear cells (MNCs) in the epidermis with intensive Fas and FasL staining. ②There was a significantly upregulated expression of Fas,FasL in uninvolved skin adjacent to the lesions and regressive lesions compared with that in progressive plaque lesions, as well as in normal skin. Conclusion The downregulated expression of Fas and FasL and increased infiltration of MNCs might contribute to ineffective immunosurveillance and immunoregulation in psoriatic lesions, which might be involved in the pathogenesis of psoriasis.

Key words: Psoriasis, Fas, Fas ligand, Apoptosis