A case of chronic lymphocytic leukemia with properties characteristic of natural killer cells

A case of chronic lymphocytic leukemia that consisted of a homogeneous population of cells that had properties similar to those described for natural killer (NK) cells is presented. These leukemic cells had a morphology of large granular lymphocytes (LGL) and receptors for sheep erythrocytes (ER) and for the Fc portion of IgG (Fc gamma-R). They expressed pan-T antigens OKT3 and Leu-4, but neither helper/inducer T- cell differentiation antigens OKT4 and Leu-3a nor cytotoxic/suppressor T-antigens OKT8 and Leu-2a. HNK 1 antigen, which can be expressed on human NK cells, could be detected on almost all leukemic cells (LGL), whereas a myeloid differentiation antigen, OKM1, which can be expressed on macrophages, granulocytes, and NK cells, was not detected. Thus, it was concluded that the leukemia cells had a characteristic profile of the surface markers: ER+, Fc gamma-R+, HNK-1+, OKT3+, Leu-4+, OKT4-, OKT8-, Leu-3a, Leu-2a, and OKM1-. Although freshly isolated leukemic cells showed no cytotoxicity on NK targets, after incubation at 37 degrees C, the cells did show a potent cytotoxicity on targets of erythroleukemic cell, T cell, and monocyte (but not B cell) origins. When the cells were incubated at 37 degrees C, interferon (IFN gamma) was spontaneously produced in the culture fluids. Treatment with anti- HNK-1 and complement completely abrogated expression of NK activity and interferon production of the patient's lymphocytes in culture. These characteristic features of surface markers and functions strongly suggest the possibility that the leukemia cells of this case are of NK cell origin. The relationship between this case and chronic lymphocytic leukemia of T-cell origin is discussed.