Auto-anti-anti-DNA antibodies from SLE patients and normals

Cross reacting auto-anti-idiotypic antibodies against anti-ssDNA antibodies were investigated in patients with systemic lupus erythematosus (SLE) and normals. Sera or immunoglobulins from SLE and normals depleted of anti-ssDNA activity and DNA antigen inhibited the reaction between 125I-F(ab')2 anti-ssDNA and ssDNA. In addition, binding to F(ab')2 portions of chromatographically purified portions of anti-ssDNA coated on polystyrene wells could be measured both in depleted SLE and normal sera. Depleted sera from SLE had both greater inhibitory activity and more antibody binding capacity than depleted sera from normals. IgG from SLE sera bound to both F(ab')2 anti-ssDNA and SLE F(ab')2 non-anti-ssDNA. However, the binding of IgG to F(ab')2 anti-ssDNA was significantly inhibited by ssDNA. These results indicate that cross reacting auto-anti-anti-ssDNA as well as other antibodies to F(ab')2 portions of homologous IgG are found in higher concentration in SLE than in normals.