Demonstration of OKT 6-reactive cells in mycosis fungoides.

Infiltrates of five cases of mycosis fungoides (MF) were studied for the presence of cells reactive with a monoclonal antibody, OKT 6, which detects an antigen present on relatively immature thymocytes and Langerhans cells. In situ immunohistochemical staining was used for their demonstration. OKT 6-reactive cells formed a definite component of the dermal infiltrates of all patients examined. In three patients who showed numerous Pautrier microabscesses on routine histologic examination, OKT 6-positive cells were found to form a component of these abscesses. OKT 6-reactive cells have also recently been shown to be present in varying numbers in the dermal infiltrates of large plaque (atrophic) parapsoriasis (LPAP), a condition which may terminate in MF. The significance of these findings is discussed.