Reduction of phagocytosis and lysosomal enzyme release from human leukocytes by serum from patients with systemic lupus erythematosus.

Serums from 22 of 30 (73.3%) patients with systemic lupus erythematosus (SLE) interfered significantly with particle (zymosan) uptake and subsequent release from normal human neutrophils of lysosomal enzymes. SLE serums with low as well as those with normal functional hemolytic complement activity (CH50) suppressed phagocytosis and enzyme release despite the presence of normal serum in cell suspensions. The defect did not appear to be caused by anticomplementary activity of serum. Serums from patients whose clinical activity of disease varied from none to severe and whose treatment varied from none to high doses of prednisone were capable of suppressing phagocytosis and enzyme release. The severity of clinical SLE activity did not affect the degree of suppression. Serums from patients treated with corticosteroids were more inhibitory than serums from patients not so treated. The nature of the inhibitor is unknown.