Inhibition of natural killer cell activity by serum from patients with systemic lupus erythematosus: roles of disease activity and serum interferon.

Among their immunological alterations patients with systemic lupus erythematosus (SLE) have been shown to have diminished natural killer (NK) cell activity. This abnormality is at least in part related to humoral factors, as sera from patients with SLE can inhibit the NK activity of peripheral blood mononuclear cells from normal individuals. The present study extends these findings to demonstrate that the inhibitory ability of sera from patients with SLE varies with disease activity. Furthermore, sera from patients with active SLE containing interferon (IFN), a potent stimulator of NK activity, were equally or more inhibitory than sera which did not contain IFN. Thus the factors in SLE sera which can inhibit NK function vary with disease activity and cannot be overcome by IFN present in these sera.