Demonstration of Ia-like antigens on T lymphocytes in lesions of psoriasis, lichen planus and discoid lupus erythematosus.

A combined indirect immunofluorescence technique with a murine monoclonal antibody against human Ia-like antigens (OKIal) and an IgG F(ab')2 preparation of a rabbit anti-T lymphocyte serum was used to study Ia-like antigens on T lymphocytes in skin lesions of psoriasis, lichen planus and discoid lupus erythematosus. The majority of the T lymphocytes in the various skin lesions expressed Ia-like antigens. T lymphocytes expressing Ia-like antigens were also demonstrated in the dermis and the epidermis in sections of unaffected skin, although of a markedly lower proportion than in affected skin. The results may indicate that the T lymphocytes in these skin lesions are activated cells involved in cell-mediated immune reactions.