Effect of agents which block steroid receptor-DNA interaction on anti-DNA antibody titers in sera of patients with systemic lupus erythematosus.
We studied whether agents capable of blocking the interaction between steroid receptors and DNA could inhibit the serologic reactivity of anti-nuclear, and other, autoantibodies found in sera of humans with autoimmune disease. Conventional immunofluorescence procedures were used for both detection and titration of these autoantibodies. Parallel studies were conducted with sera diluted in buffers containing the inhibitory agents; KCl, Na2MoO4 or 1,10-phenanthroline, at optimal or suboptimal levels for blocking the steroid receptor-DNA interaction. In most cases these agents had no significant effect on the titer of autoantibodies present in human sera. However, there was one notable exception, that of autoantibodies to native DNA found in sera of patients' with systemic lupus erythematosus and detected by indirect immunofluorescence using Crithidia luciliae kinetoplast DNA as substrate. Here these agents caused either total inhibition of serologic reactivity at optimal blocking concentrations, or a significant reduction in titer, in all twelve specimens studied. These results give rise to at least two possible interpretations: (1) antibodies to native DNA are unusual with respect to the ease with which their binding to antigen may be inhibited by these three chemically unrelated compounds, and (2) steroid receptors are somehow involved in the binding of these antibodies to native DNA.