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, 3I, and 8.1 2, and 70 for expression of F4 and 3I. 31.3% showed at least one anti- DNA Id marker and many cationic myelomas were also positive for anti-D NA ELISA reactivity as well as anti-F(ab')(2). Five M-components showe d anti-nucleosome reactivity and one without detectable anti-DNA Id ma rkers showed very strong anti-nucleosome antibody which was also inhib ited by DNA and Sm antigens. Anti-idiotypic antisera produced either a gainst Id(+) anti-DNA reactive M components or F(ab')(2) fragments of affinity purified SLE IgG anti-DNA showed preferential cross-reactive idiotype reactivity between Id(+) anti-DNA reactive M components. Our findings indicate that human IgG monoclonal proteins positive for seve ral common anti-DNA Ids and possessing anti-DNA ELISA reactivity, can serve as models for SLE Id marker antigens and as a source to prepare anti-Ids from IVIG.