Phenotypic analyses of lymphokine-activated killer cells that release interferon gamma and tumor necrosis factor alpha.

We recently reported that interleukin-2(IL-2)-activated peripheral blood lymphocytes and CD3+, lymphokine-activated killer (LAK) cell clones release tumor necrosis factor alpha(TNF alpha) and interferon gamma (IFN gamma) when stimulated with K562 erythroleukemia cells. We examined the phenotype of IL-2-activated peripheral blood leukocytes that secrete TNF alpha and IFN gamma when stimulated with K562 cells and demonstrated that TNF alpha secretion is not due to the presence of contaminating mononuclear phagocytes. Further, we demonstrate that IL-2-activated natural killer (NK) cells release only IFN gamma when stimulated with K562 cells while T lymphocytes exposed to monoclonal anti-CD3 and K562 cells secrete both TNF alpha and IFN gamma. However, T cells stimulated only with K562 cells did not release IFN gamma or TNF alpha while the admixture of these T cells with NK cells, when stimulated with K562 cells, released levels of TNF alpha comparable to those produced by the unseparated cells. At present it is unclear whether only one or both effector cell types respond to K562 by releasing TNF alpha or why the presence both cell types is needed.