Antibodies to single-stranded DNA in patients with discoid lupus erythematosus

Sera from 31 patients with discoid lupus erythematosus were examined for the presence of antibodies to single-stranded and native DNA. None of these sera had antibodies to native DNA. When rabbit anti-human IgM was used, 6 of 28 patients had elevated binding, whereas only 1 of 29 patients had abnormal binding when antiIgG was used. The IgM nature of this response was confirmed when we demonstrated the binding activity in heavy fractions from gel filtration. We concluded that at least one-fifth of patients with discoid lupus erythematosus have IgM antibodies to single-stranded DNA.