Lymphokine induction of NK-like cytotoxicity in T cells from B-CLL

T cells from patients with B cell chronic lymphocytic leukemia (B-CLL) exhibit defective natural killer (NK) activity. In this study, we have analyzed the cytotoxic-inducer effects of gamma interferon (gamma-IFN) and supernatants containing interleukin 2 (IL 2 sup). T cells from patients with B-CLL were incubated with gamma-IFN or IL 2 sup. gamma-IFN did not modulate the very low or undetectable levels of NK activity present in the T cell population. However, the IL 2 sup induced a potent cellular cytotoxicity against NK-sensitive and NK-resistant tumoral target cells. This cytotoxic inducer effect (a) was present in lectin-free IL 2 sup and in a 15,000- to 20,000-dalton molecular weight fraction obtained by gel filtration chromatography of this supernatant; (b) was directed against NK-sensitive and NK-resistant target cells; (c) was not correlated with the basal levels of NK activity; and (d) was not associated with a development or augmentation of the proportion of lymphocytes with classic NK cell phenotype. Taken together, these results demonstrate that unstimulated T cells from B-CLL patients, incubated briefly (18 hours) with IL 2 sup but not gamma-IFN, have strong NK-like cytotoxicity, despite the lack of classic NK activity.