The effect of adherent cell-derived factors on immunoglobulin and anti-DNA synthesis in systemic lupus erythematosus

Abstract

The role of adherent cells in the regulation of anti-DNA and immunoglobulin synthesis was investigated in patients with systemic lupus erythematosus (SLE). Peripheral blood mononuclear cells were cultured for 7 days, or were washed after 20 hr of incubation and recultured in fresh media. This washing resulted in a marked decrease in total IgG, IgM, and anti-DNA synthesis compared with unwashed cultures. Reculturing the washed cells in their original supernatant reconstituted Ig and anti-DNA synthesis. Hence it appeared that a supernatant factor, or factors, present in the first 20 hr of mononuclear cell cultures, was required for maximal Ig synthesis. Adherent cells were found to be the source of this Ig-stimulating activity. Moreover, adherent cell supernatants had no direct Ig-stimulating effect on B cells. Ig synthesis was stimulated, however, when T cells where present with the B cells at a 3:1 ratio. Autologous SLE mononuclear cell supernatants reconstituted Ig synthesis to a greater degree than did autologous normal supernatants. SLE adherent cell supernatants were fractionated on an HPLC sizing column. The fractions were tested for their ability to stimulate IgG synthesis by SLE mononuclear cells that had been washed after 20 hr of culture. A single peak of IgG-stimulating activity was found at approximately 14,000 M r. A rabbit antiserum to interleukin-1 (IL-1) neutralized the 1g-stimulating activity in adherent cell supernatants. No correlations were found, however, between supernatant IL-1 levels assayed by C3H-HeJ mouse thymocyte proliferation and IgG stimulation in mononuclear cell cultures, suggesting that the effects of IL-1 on cell proliferation may not accurately reflect its effects on Ig synthesis. These observations suggest that in normal individuals and in patients with SLE in vitro polyclonal Ig and anti-DNA synthesis requires the presence of soluble adherent cell factors. The Ig-stimulating effect is facilitated by T cells and appears to be mediated at least in part by IL-1. This culture technique provides a new way of analyzing the role of soluble factors in autoantibody synthesis and suggests that IL-1 may be an important contributor to lupus B-cell hyperactivity.