A case of T-cell chronic lymphocytic leukemia with an unusual phenotype and central nervous system involvement.

A case of T-cell chronic lymphocytic leukemia is reported. The leukemic cells had the morphologic features of medium-sized, mature-looking lymphocytes, and had an affinity for the central nervous system. Cytochemically, they were positive for alpha-naphthyl acetate esterase and acid phosphatase. They formed E-rosettes (E+) and reacted with OKT11 but not with OKT3/Leu-4, OKT4/Leu-3, OKT8/Leu-2, or OKM1, and did not possess IgG-Fc receptors (Fc gamma R). Functionally, they did not respond to phytohemagglutinin or concanavalin A, were not natural killer cells or antibody-dependent as well as alloantigen-reactive killer cells. Furthermore, they did not possess a helper or suppressor T-cell function for immunoglobulin synthesis. Results of immunologic studies suggest that the leukemic cells were derived from a normal counterpart of a lymphocyte subset present as a minor component of the peripheral blood, namely an E+, OKT3-, OKM1-, Fc gamma R- subset, the function of which is not yet identified.