The cell population in the cutaneous infiltrate of mycosis fungoides: in situ studies using monoclonal antisera

T cell antigens were studied in cutaneous sections from five patients with mycosis fungoides (MF). The method allowed cell counting to be undertaken for each monoclonal antiserum. OKT3 (pan T cell) antiserum confirmed the predominantly T lymphocytic nature of the infiltrate, labelling the majority of infiltrating cells. OKT4 (helper/inducer) antiserum positively labelled 90% of the lymphocytes identified as OKT3⁺. OKT8 (suppressor) antiserum marked only single or small groups of dermal lymphocytes, which comprised 24% of the cells identified as T lymphocytes. OKT6 (anti-Langerhans) showed positive labelling of dendritic cells in the epidermis and dermis. Fewer positively labelled epidermal dendritic cells were observed in sections from patients receiving PUVA, but no difference was found in the number of OKT6 positive dermal cells. The ratio of helper to suppressor cells in the dermal infiltrate significantly exceeded the normal circulating ratio.