Characterization of Cross-Reactive Anti-DNA Autoantibodies in Murine Lupus

Abstract

The role of crossreactive anti-DNA autoantibodies in the pathogenesis of Systemic Lupus Erythematosus (SLE) and its counterpart in the mouse (murine lupus) remains undefined. Five murine monoclonal anti-DNA autoantibodies tested in ELISA and immunofluorescence assays were found to cross-react with a variety of both nucleic acid and non-nucleic acid antigens. These included double stranded DNA (dsDNA), single stranded DNA (ssDNA), transfer RNA (tRNA), and the murine thymoma cell lines WEHI-22, WEHI-7, and EL-4. The majority of the autoantibodies reacted with all antigens tested; none of the autoantibodies reacted with only one antigen. To determine if the multiple reactivities demonstrated by these hybridoma-derived monoclonal anti-DNA autoantibodies accurately reflects the in vivo, autoimmune environment, the same assays were used to measure the reactivities of autoantibodies secreted directly from unfused autoimmune spleen cells cultured in vitro. These spleen cell-derived autoantibodies were found to display reactivities very similar to those demonstrated by the monoclonal anti-DNA autoantibodies indicating that the hybridoma process itself does not appear to select and amplify reactivities which are not present in vivo. Initial molecular characterization of F11, a monoclonal anti-DNA autoantibody crossreactive with both dsDNA and ssDNA, revealed that it utilizes the same VH gene segment as an anti-DNA autoantibody specific for ssDNA. F11 was also found to utilize similar VH, D, and JH gene segments as an antibody directed against the hapten polymer (Glutamic acid⁶⁰,Alanine³⁰, Tyrosine ¹⁰)n (GAT). Thus, the same Ig gene segments used to encode crossreactive anti-DNA autoantibodies can also be utilized by anti-DNA autoantibodies displaying strict antigen specificity as well as by antibodies directed against exogenous antigens.