IDENTIFICATION AND SEQUENCE OF THE IMMUNOGLOBULIN HEAVY CHAIN VARIABLE REGION GENE INVOLVED IN CODING FOR AN ANTI-DNA AUTOANTIBODY.

Abstract

The major pathologic feature of the human autoimmune disease Systemic Lupus Erythematosus (SLE) and its murine counterpart, murine lupus, is the production of autoantibodies to nucleic acid antigens. In this study, a panel of six murine monoclonal anti-DNA autoantibodies was characterized at both the cellular and molecular levels in order to determine their possible role in the etiology of autoimmune disease. At the cellular level the autoantibodies were found to be highly cross-reactive, binding to three different antigenic forms of DNA as well as to the cell surface of various lymphoid cell lines. Furthermore, the fact that this autoantibody binding could be abrogated by pretreating the cells with either Proteinase K or DNase supports the hypothesis that a DNA binding protein may exist on the cell surface and that DNA bound to this receptor may serve as the target for the anti-DNA autoantibody. At the molecular level, the immunoglobulin (Ig) gene segments (V(H), D, J(H)) used to encode the variable region of the heavy chain of an anti-DNA autoantibody were sequenced. All three gene segments could be identified as members of established Ig gene segment families. In fact, the heavy chain of an antibody directed against the hapten L-glutamine₆₀-L-alanine₃₀-L-tyrosine₁₀ polymer (GAT) was found to utilize the same combination of V(H), D, and J(H) gene segments as the anti-DNA autoantibody. These results clearly indicate that autoantibodies are encoded by gene segments from the same Ig gene families used to encode antibodies to exogenous antigens. However, the discovery that this anti-DNA autoantibody is encoded by the same V(H) gene segment which encodes another anti-DNA autoantibody, derived from a different autoimmune mouse strain, supports the idea that certain V(H) gene segments may, in fact, be preferentially used to encode autoantibodies.