Natural antibodies in sera of patients with systemic lupus erythematosus

Sera obtained from fifty-five patients with active systemic lupus erythematosus (SLE) and from four patients with mixed connective tissue disease (MCTD) previously shown by immunofluorescence and by double immunodiffusion to possess antinuclear antibodies, were tested for the presence of natural antibodies of IgG, IgA, and IgM isotypes. Antibody activity to actin, myosin, DNA, TNP, albumin, and tubulin was examined, using an enzyme-linked immunosorbent assay (ELISA). It was found that, in comparison with the antibody titers in normal sera, most of the SLE and MCTD sera possessed statistically greater amounts of IgG, IgA, and IgM antibodies directed against all the antigens tested. Furthermore, the IgG, IgA, and IgM antibody activity to DNA and TNP, compared to that found with all the other antigens, was significantly higher. Antibodies reacting with a saline extract of calf thymus (ECT) were studied by ELISA and by immunodiffusion. No correlation was observed between the natural antibody titers and the serum antibody levels to ECT detected either by ELISA or by immunodiffusion.