Use of Orthoclone monoclonal antibodies in the study of selected dermatologic conditions.

Monoclonal antibodies recognizing human T cell differentiation antigens were used to study lymphocyte populations in three cutaneous diseases. Neoplastic lymphocytes from patients with varying phases of cutaneous T cell lymphoma (mycosis fungoides, Sezary syndrome and related presentations) were reactive with OKT1 and OKT3 (pan T cell reagents) and OKT4 (an antibody defining the functional "helper" T cell subset). The malignant cells lacked membrane antigens reactive with OKT5 and OKT8 (markers of "suppressor" T cells). The presence of an OKT1+, OKT3+, OKT4+, OKT5-, OKT8- phenotype on the neoplastic T lymphocytes of cutaneous T cell lymphoma (CTCL) supports the clinical impression that all phases of CTCL represent a single disease entity. A patient with pemphigus vulgaris, a disease of autoreactive, antiepidermal antibodies was shown to consistently have a marked expansion of the peripheral blood OKT4 reactive T lymphocyte population. These findings suggest that autoantibodies in pemphigus vulgaris may occur in the context of a profound OKT4/OKT5 immunoregulatory imbalance. Peripheral blood lymphocytes from patients ith extensive psoriasis vulgaris had a normal profile of reactivity with the OKT antibodies. In addition, OKT6 (marker of intrathymic T cells) has been shown to react with Ia+ dendritic cells in the epidermis suggesting that this antibody may recognize Langerhans' cells.