Antinucleic acid autoantibody responses of normal human origin: antigen specificity and idiotypic characteristics compared to patients with systemic lupus erythematosus and patients with monoclonal IgM.

One idiotype family 4.6.3 derived from a human hybridoma IgML monoclonal anti-DNA antibody of normal origin is commonly expressed (approximately 85%) in the serum of patients with systemic lupus erythematosus but not in normal controls, where its level appears to fluctuate with clinical disease activity. In contrast, the IgM released by normal cultured lymphocytes in vitro expresses this idiotype family but does not bind DNA. Both idiotype 4.6.3 and anti-DNA antibodies are frequently detectable in the serum of patients with monoclonal IgM but not IgG. Therefore, it is likely that idiotype 4.6.3 reflects the expression of a common germ line immunoglobulin gene family. Some of the IgM molecules encoded by these germ line immunoglobulin genes also bind DNA.