Natural killer-interferon system in patients with preleukaemic states.

The natural killer (NK)-interferon (IFN) system was investigated in patients with preleukaemic states. Endogenous NK cell activity was markedly reduced in all 12 patients studied. No significant correlation was observed between the activity of NK cells and the percentage of blast cells in the peripheral blood or bone marrow. The frequency of large granular lymphocytes (LGL) in lymphocytes of the peripheral blood was not reduced in most patients. The percentage of target binding cells in patients was essentially the same as that in normal controls, and the activity of NK cells from normal donors was not affected by the coexistence of mononuclear cells obtained from the peripheral blood of patients. Furthermore, the alpha-IFN production in response to HeLa cells persistently infected with measles virus was reduced in all patients studied, except for one case with acquired idiopathic sideroblastic anaemia. The augmented activity of NK cells induced by alpha-IFN was variable, but remained at lower levels than the endogenous activity of NK cells in normal controls. These findings suggest that not only the intrinsic defect and reduced number of NK cells but also the dysfunction of the NK-IFN system may be responsible for the reduced activity of NK cells in patients with preleukaemic states.