Benign monoclonal gammopathy with IgG anti-DNA, anti-Sm and anti-F(ab')2 activity.

ABSTRACT

OBJECTIVE: To study anti-DNA idiotypic markers and anti-DNA activity in human monoclonal immunoglobulin proteins. METHODS: Seventy human IgG M-components intentionally selected for cationic electrophoretic characteristics were studied for F4 and 31 anti-DNA idiotypic markers and anti-DNA as well as anti-F(ab')2 antibody activity. RESULTS: Eight of 70 M-components showed significant anti-DNA activity. In two both anti-DNA and anti-F(ab')2 activity occurred together. One IgG-2 kappa M-component showed extremely high anti-ds DNA, anti-Sm, anti-F(ab')2 and anti-Sm/ RNP ELISA activity. Cross inhibition studies showed that each reactive antigen inhibited the other. N-terminal V-region sequencing showed the VH3, VK3 subgroup. Anti-idiotypic rabbit antibody produced against this M-component showed strong reactivity with affinity purified IgG anti-DNA and anti-F(ab')2 from most SLE patients and normal subjects. CONCLUSION: Monoclonal human immunoglobulins may contain multiple autoantibody specificities including anti-DNA; anti-Sm, anti-Sm/RNP, and anti-F(ab')2. Many antibodies with these specificities share common V-region antigens. Such relationships could contribute to idiotypic immune regulation and control.