Natural autoantibodies in systemic lupus erythematosus.

We have tested the sera of 25 patients with systemic lupus erythematosus (SLE) for antibody activity against a panel of six antigens: DNA, TNP, actin, tubulin, myosin, albumin. Eluates from renal biopsy tissue were also tested. Sera from patients with lupus nephritis were found to contain high titres of IgA antibodies directed against the antigens of the panel, and marked IgG anti-DNA and anti-TNP antibody activity. The IgG anti-TNP antibodies isolated from SLE serum by affinity chromatography on a TNP-immunoadsorbent, were also found to possess anti-DNA activity. Kidney eluates obtained from biopsy specimens of SLE patients contained IgG antibodies strictly specific for DNA in three out of the nine patients tested, while three eluates from the remaining six patients reacted with DNA and TNP and three with DNA and all the other antigens of the panel. These results strongly suggest that in SLE sera there are at least three populations of circulating anti-DNA antibodies: those strictly specific for DNA, those recognizing DNA and TNP and those recognizing DNA and other macromolecules. Furthermore, because six out of nine of the eluates contained antibodies with an absolute or restricted specificity for DNA, this suggests that these antibodies are more often pathogenic than the polyspecific ones recognizing DNA and other macromolecules.