Cationic Myeloma M-components Frequently Show Cross-reacting Anti-DNA, Anti-F(ab)2 and Anti-nucleosome Specificities

134 cationic human IgG myeloma proteins were studied for expression of anti-DNA Idiotypic markers 64 were studied for 16/6, F4, 31, and 8.12, and 70 for expression of F4 and. 11. 11.1% showed at least one anti-DNA Id marker and many cation ic myelomas were also positive for anti-DNA EL1SA reactivity as well as anti-F(ab')2- Five M-components showed anti-nucleosome reactivity and one without delectable anti-DNA Id markers showed very strong anti-nucleosome antibody which was also inhibited by DNA and Sm antigens. Antiidiotype anlisera produced either against ld(+) anti-DNA reactive M components or F(ab')2 fragments of affinity purified SLE IgG anti-DNA showed preferential cross-reactive idiolype reactivity between Id(+) anti-DNA reactive M components. Our findings indicate that human IgG monoclonal proteins positive lor several common anti-DNA Ids and possessing anti-DNA FMSA reactivity, can serve as models for SLE Id marker antigens and as a source to prepare anti-Ids from IVIG.