The Membrane Phenotype of T‐Prolymphocytic Leukaemia

Abstract

Cells from 13 cases of T prolymphocytic leukemia (T-PLL) were studied with a battery of immunological techniques in order to define their membrane phenotype. All cases were E[erythrocyte]-rosette positive and were negative with OKT6, anti-HLA-DR, anti-Ig and M-rosettes; in 3, 20-30% of the cells had receptors for C3b [complement component 3b], 7 cases had predominantly a helper/inducer T-subset phenotype, (OKT4+, OKT8-) and 4 had a suppressor/cytotoxic phenotype (OKT8+, OKT4-). Cells in 2 cases coexpressed OKT4 and OKT8 in 48% and 95% of prolymphocytes and in another, both OKT4 and OKT8 were negative. Terminal transferase (TdT) was negative by immunofluorescence in all the cases, but a low positive level was detected biochemically in 1. Although T-PLL appears to be heterogenous in respect of membrane phenotype, the observation of unexpected features in 8 of the cases raises the possibility that it may originate in a cell of intermediate maturation between late thymocytes and mature T lymphocytes. These features plus the clinical manifestation of the disease.sbd.typical morphology, splenomegaly, lymphadenopathy, skin lesions, high WBC and aggressive clinical course.sbd.help define T-PLL as a distinct clinicopathological entity.