Functional diversity within the suppressor phenotype as defined by monoclonal antibody in T-cell prolymphocytic leukemia.

A patient with T-cell prolymphocytic leukemia (T-PLL) is described. The malignant T-cells from the patient were predominantly Leu-2-positive, indicating a suppressor phenotype. The cells were then tested to determine their functional capabilities. The patient's Leu-2-positive cells initially suppressed B-cell proliferation, as predicted by their phenotype but later functioned as T helper cells in the pokeweed mitogen system without a change in phenotype. The cells also responded inadequately to alloantigen and mitogen despite addition of exogenous T-cell growth factor (TCGF). Leu-2-positive prolymphocytes from the spleen of the patient were constitutive producers of TCGF. Surface phenotype using monoclonal antibody was inadequate to predict T-cell function of the cells from this patient with T-PLL. In addition, these data suggest there may be functional subpopulations within the OKT8+ phenotype. Constitutive TCGF production by malignant post-thymic T-cells may represent a mechanism by which these cells sustain their own growth.