An OKT4+ T-cell population with suppressor activity in Sézary syndrome.

This report describes a case of Sézary syndrome with the surface marker phenotype of a mature distinct T-cell subset OKT3+, OKT4+, OKT8-, OKT17+, OKIal-(+). Functional studies indicated that the patient's peripheral blood cells showed a very low proliferative response to non-specific mitogens (phytohaemagglutinin, concanavalin A, pokeweed mitogen) and failed to differentiate into plasma cells in a pokeweed mitogen--immunoglobulin-synthesis-driven system. In coculture with normal cells the leukaemic cells were able to suppress lectin-induced T-cell proliferation and B-cell differentiation in a dose-dependent manner. Suppressor function was not radiosensitive and did not require the presence of the OKT8+ subset for expression. These Sézary cells thus represent a suppressive T-cell subset within the OKT4+ population. This subset may well correspond to the recently described OKT4+, OKT17+ normal suppressor cells. These findings would therefore illustrate a pathological and possibly clonal expansion of a normal OKT4+ suppressor T-cell subset.