EXPRESSION OF IMMUNOASSOCIATED SURFACE-ANTIGENS IN PSORIASIS OCCURRING ON VITILIGINOUS SKIN

We report a case of psoriasis occurring on vitiliginous skin, in which most plaques were localized to vitiliginous rather than uninvolved sk in. In order to determine the reason for the predilection of psoriasis to develop on vitiliginous skin in the patient, we studied local immu ne mechanisms in this skin lesions. Using the avidin-biotin peroxidase method, the immuno-histochemical localization of ICAM-1 (intercellula r adhesion molecule-1), LFA-1 (lymphocyte function - associated antige n-1), HLA-DR (human leukocyte antigen-DR), OKT-6, and subpopulations o f lymphocytes were studied in psoriatic lesions on vitiliginous skin, in vitiliginous skin without psoriasis, and in adjacent uninvolved ski n. Expression of ICAM-1 and HLA-DR by keratinocytes was observed in ps oriasis on vitiligo, but ICAM-1 was not in the epidermis of vitiligino us or adjacent uninvolved skin. LFA-1-positive lymphocytes had infiltr ated the epidermis and dermis in regions of psoriasis on vitiligo. The dermal infiltrates in regions of psoriasis on vitiligo consisted prin cipally of LFA-1-, CD3- and CD4-positive lymphocytes, while in the epi dermis a few CD3- and CD8-positive lymphocytes were observable. The pa ttern of expression of immunosurface antigens such as ICAM-1, LFA-1, H LA-DR, and OKT-6 in regions of psoriasis on vitiligo was characteristi c of psoriasis vulgaris, and not of vitiligo vulgaris.