Lack of natural antibodies in rheumatic diseases.

The prevalence and Ig class of natural antibodies in the sera of healthy individuals and of patients with rheumatic diseases were studied. The presence, even in high concentrations, of natural antibodies in normals was confirmed. In the rheumatic diseases tested, however, a discordance in the levels and Ig class of anti-actin, anti-myosin and anti-ssDNA antibodies was noted. IgM anti-actin antibodies occur infrequently, whereas IgM anti-myosin and anti-ssDNA are increased in these diseases. IgG anti-actin antibodies are increased in the sera of patients with RA, but not in patients with SLE, polymyositis or mixed connective tissue disease (MCTD). IgG anti-myosin as well as anti-ssDNA antibodies were increased in patients with RA and SLE, but not in patients with polymyositis or MCTD. These findings suggest that these natural antibodies are unlike the multispecific autoantibodies produced by lymphocytes from the CD5+ B cell lineage and that they may have undergone affinity maturation. Perhaps natural antibodies are a feature of health rather than of disease.