Interactions of IgG from SLE patients with peripheral blood mononuclear cells and adherent cell populations

Peripheral blood mononuclear cells (PBMCs) from normal control subjects were studied for their interactions with IgG isolated from normal or active systemic lupus erythematosus (SLE) sera. Preincubation of PBMCs with SLE IgG at 0.5-1.0 mg for 24 h followed by washing and subsequent cell culture for 7 days resulted in marked relative increase in cell supernatant IgG. These findings were noted with and without inclusion of cyclosporin A or indomethacin in cultures. Experiments using isolated normal adherent cell populations showed that SLE IgG but not normal IgG, when preincubated with adherent cell macrophage/monocyte populations, was capable of inducing the latter to produce suppressor factors capable of down modulating IgG production or release from normal non-adherent cells cultured with pokeweed mitogen. These findings suggest that IgG from active SLE patients may interact with both IgG-producing PBMC populations as well as adherent-cell populations to influence IgG production or release from subsequently cultured cells.