The γG subclass of antinuclear and antinucleic acid antibodies

Selected sera from patients with systemic lupus erythematosus (SLE) and progressive systemic sclerosis (PSS) were studied to determine the γG subclass in which the antibody activities were present. These sera were known to contain γG antibodies to nuclear antigens, cytoplasmic antigens or nucleic acids. Antibodies to DNA and those giving a peripheral pattern in the fluorescent antinuclear antibody test (ANF) primarily were of the γG1 and γG3 types; antibodies giving a speckled pattern primarily were of the γG3 type; and antibodies giving a diffuse pattern in the ANA test primarily were of the γG3 type, and less so of the γG1 type. These findings indicate: that antibodies to some nuclear antigens and nucleic acids may be restricted to certain γG subclasses; and that anti‐DNA antibodies, which have been most strongly associated with low serum complement levels and active lupus nephritis, are found primarily in those γG subclasses which fix complement most efficiently—namely, γG1 and γG3.