Inhibition of clonogenic growth of fresh leukemia cells by unstimulated and IL-2 stimulated NK cells of normal donors.

We have demonstrated that unstimulated highly-enriched NK cells have the capability to inhibit the growth of fresh clonogenic leukemic cells from AML, CML and preleukemic patients. The NK-cell population mediating antileukemic reactivity exhibited LGL morphology and NKH1 and CD16 phenotype. The inhibition of leukemic growth could be mediated by cell-to-cell contact or by soluble factor produced by NK cells. Antileukemia activity was only detectable when enriched population of LGL was utilized; NW-filtered lymphocyte population did not exhibit leukemia-inhibitory effect. However, such activity could be generated after culture of the latter effector cells with IL-2. The leukemia directed IL-2 activated effector cells were characterized as NK cells. The data reported here provide new insight into host factors which may control leukemia growth and indicate the possible future application of NK cells for therapy of leukemia.