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 skin. In order to determine the reason for the predilection of psoriasis to develop on vitiliginous skin in the patient, we studied local immune mechanisms in this skin lesions. Using the avidin-biotin peroxidase method, the immuno-histochemical localization of ICAM-1 (intercellular adhesion molecule-1), LFA-1 (lymphocyte function - associated antigen-1), HLA-DR (human leukocyte antigen-DR), OKT-6, and subpopulations of lymphocytes were studied in psoriatic lesions on vitiliginous skin, in vitiliginous skin without psoriasis, and in adjacent uninvolved skin. Expression of ICAM-1 and HLA-DR by keratinocytes was observed in psoriasis on vitiligo, but ICAM-1 was not in the epidermis of vitiliginous or adjacent uninvolved skin. LFA-1-positive lymphocytes had infiltrated the epidermis and dermis in regions of psoriasis on vitiligo. The dermal infiltrates in regions of psoriasis on vitiligo consisted principally of LFA-1-, CD3- and CD4-positive lymphocytes, while in the epidermis a few CD3- and CD8-positive lymphocytes were observable. The pattern of expression of immunosurface antigens such as ICAM-1, LFA-1, HLA-DR, and OKT-6 in regions of psoriasis on vitiligo was characteristic of psoriasis vulgaris, and not of vitiligo vulgaris.