Decreased numbers of monocytes in inflammatory exudates in systemic lupus erythematosus.

Rebuck skin windows and delayed hypersensitivity testing were performed on patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Patients with SLE had a decreased appearance of mononuclear/macrophage cells in the inflammatory exudate compared to patients with RA and normal controls. This abnormal response was unrelated to corticosteroid therapy, but appeared to correlate with activity of disease. Impaired ability to react to skin test antigens was also demonstrated in patients with SLE. The defective mononuclear/macrophage response in patients with SLE may contribute to the impaired cell-mediated immunity and increased susceptibility to infection which occur in this disorder.