Effects of serum from patients with system lupus erythematosus on leukocyte cytotoxicity: modulation of NK activity and ADCC.

The ability of sera from patients with systemic lupus erythematosus (SLE) to alter the natural killer (NK) cell activity and antibody dependent cell mediated cytotoxicity (ADCC) of peripheral blood mononuclear cell populations from normal donors was determined employing 4-h 51Cr release assays. SLE sera significantly lowered the NK activity of both whole mononuclear cell populations (MN) (26 +/- 3% decrease) (mean +/- SEM) and lymphocyte enriched populations (24 +/- 5%) toward K562 targets when compared to results with sera from normal donors. The continuous presence of serum was not required for this effect since MN effector cells preincubated with sera and then washed also exhibited diminished NK activity. SLE sera decreased only slightly lymphocyte-mediated ADCC to either erythrocyte (human 0 + RBC) or tumor cell (human CEM T lymphoblast) targets. ADCC by isolated monocytes, however, was significantly diminished by SLE sera (54 +/- 5%). These data suggest that in patients with SLE, serum factors may be responsible for alteration of both NK activity and ADCC.