ANTIBODY-DEPENDENT CELL-MEDIATED CYTOTOXICITY IN SELECTED AUTOIMMUNE-DISEASES

Antibody-dependent cell-mediated cytotoxicity mediated by perpheral blood lymphocytes was studied in patients with systemic lupus erythematosus, polyarteritis nodosa, Sjogren''s syndrome and rheumatoid arthritis. The target cells were chicken erythrocytes coated with rabbit anti-chicken erythrocyte antibody. Antibody-dependent cell-mediated cytotoxic activity was normal in Sjogren''s syndrome and rheumatoid arthritis but significantly decreased (P < 0.001) in active systemic lupus erythematosus and in 2 patients with polyarteritis nodosa. A partial regeneration of antibody-dependent cell-mediated cytotoxic activity was obtained by treatment with pronase and DNase followed by overnight incubation. Sera from patients with systemic lupus erythematosus inhibited antibody-dependent cell-mediated cytotoxic activity of normal lymphocytes. The inhibitory activity was studied by specific immunadosorption and sucrose density gradient ultrancentrifugation. Removal of IgG [immunoglobulin G], but not IgM greatly reduced inhibition. Inhibitory factors were present in 7S and heavier fractions containing IgG. Five systemic lupus erythematosus patients were studied serially to determine if improvement in clinical status could be correlated with a decrease in serum inhibitory factors as studied by inhibition of normal antibody-dependent cell-mediated cytotoxicity. A greater serum inhibitory capacity was found in each patient during periods of greater disease activity.