[Analysis of anti-DNA antibody in sera from patients with systemic lupus erythematosus by isoelectric focusing with respect to autoantibody isotype and immune complex].

Systemic lupus erythematosus (SLE) is an autoimmune disease manifested by the production of autoantibodies which leads to an array of clinical symptoms. Among these autoantibodies, anti-DNA antibodies play a major role, since resulted DNA/anti-DNA immune complexes(IC) cause glomerulonephritis and other autoimmune local lesions in SLE. In this report, spectrotypes of anti-DNA antibodies of IgG, IgA and IgM classes, and IC were studied by isoelectric focusing. The size of IC was also studied. Anti-DNA autoantibodies in the sera of SLE patients were found mainly in IgG class, however, those of IgA and IgM classes were detected as minor subpopulations. By electrofocusing, both IgA and IgM anti-DNA antibodies were focused to relatively restricted acidic regions. In contrast, IgG anti-DNA antibodies were focused to two distinct pH regions; one was the acidic region similar to that IgA and IgM antibodies migrated (pH 3.2 to 6.0), and the other to far basic region between pH range of 7.8 and 10.0. IC was focused to the same basic region as a fraction of IgG migrated. Anti-DNA antibodies of IgG class, especially those focused to alkaline pH region (cationic antibodies) bound to phenylalanine (PH) column with high affinity. From these results, it was inferred that anti-DNA antibodies of IgG classes, especially those having high basic charge (cationic antibodies) showed a tendency to form IC and that the cationic antibodies may participate in the pathogenesis of tissue injury, especially of glomerulonephritis, in SLE.