Phenotypic analyses of lymphokine-activated killer cells that release interferon γ and tumor necrosis factor α

We recently reported that interleukin-2(IL-2)-activated peripheral blood lymphocytes and CD3⁺, lymphokine-activated killer (LAK) cell clones release tumor necrosis factor α(TNFα) and interferon γ (IFNγ) when stimulated with K562 erythroleukemia cells. We examined the phenotype of IL-2-activated peripheral blood leukocytes that secrete TNFα and IFNγ when stimulated with K562 cells and demonstrated that TNFα secretion is not due to the presence of contaminating mononuclear phagocytes. Further, we demonstrate that IL-2-activated natural killer (NK) cells release only IFNγ when stimulated with K562 cells while T lymphocytes exposed to monoclonal anti-CD3 and K562 cells secrete both TNFα and IFNγ. However, T cells stimulated only with K562 cells did not release IFNγ or TNFα while the admixture of these T cells with NK cells, when stimulated with K562 cells, released levels of TNFα 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 TNFα or why the presence both cell types is needed.