The sera of 265 patients with monoclonal gammopathies were examined for the presence of a dominant idiotype of the anti-DNA antibody [16/6 idiotype (Id)] and for anti-DNA activity. An enzyme-linked immunosorbent assay (ELISA) with a rabbit anti-16/6 antibody revealed 23 (8.7%) sera that contained increased concentrations of the idiotype. Seven of the patients had benign monoclonal gammopathy, three multiple myeloma, three Waldenström macroglobulinemia, five essential mixed cryoglobulinemia, and five monoclonal cryoglobulinemia. In 5 of the 23 sera, antinuclear activity was also noted. In 11 of the 16/6 Id-positive sera the anti-nucleic acid antibody reactions were found to be polyspecific, reacting with polydeoxythymidilic acid and polyinosinic acid, in addition to single-stranded DNA and double-stranded DNA. Similar results were achieved with the purified serum monoclonal components. The specificity of the idiotype analysis was demonstrated with an unrelated dominant idiotype of anti-HBsAg antibody. In none of the patients, except one (with essential mixed cryoglobulinemia), was lupus symptomatology noted.

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The sera of 51 patients with active, untreated pulmonary tuberculosis were examined for the presence of a common anti-DNA idiotype, 1616. Thirty-four of the 57 sera (60%) had an increased level of the idiotype, as measured by enzyme-linked immunosorbent assay using a specific rabbit anti-1616 serum. Of 28 matched control sera, only 1 (4%) was found to be positive for the idiotype, The sera of patients with tuberculosis also showed increased activity against a variety of antigens with which lupus autoantibodies are known to crossreact (e.g., single-stranded DNA, double-stranded DNA, polynucleotides, and cardiolipin). A correlation was observed between serum IgG and IgM levels and the 1616 idiotype levels.