Cloning and Sequencing of Murine Lupus-Associated Autoantibody Genes

Abstract

Immunoglobulin (Ig) heavy (H) and light (L) chain variable (V) region genes are assembled somatically during B-cell differentiation by stage-specific DNA rearrangements of multiple V, diversity (D, H chains only), and joining (J) germline gene segments (reviewed by Alt et al, 1986). Different combinations and imprecise joining of V, D and J elements, random insertion of nucleotides during the joining process (N regions), as well as somatic mutation, contribute to the generation of antibody diversity and ultimately determine the specificity (self or non-self antigen) of a given antibody. Murine lupus is characterised by high titres of circulating autoantibodies (AAb) leading to immune complex mediated lesions (Theofilopoulos and Dixon, 1985). We have previously shown, by means of restriction fragment length polymorphism analysis, that lupus mice and non-lupus mice of the same haplotypes share highly conserved H chain variable region loci (Kofler et al., 1985b). In the present study, we report a detailed analysis of nucleotide sequences corresponding to H and L chains of nine monoclonal AAb with different specificities frequently expressed during lupus disease (single stranded DNA, histone and various Ig isotypes). The following questions were addressed: Arc there any primary structures common to ail AAb regardless of their specificity, which might signal their autoreactive nature? Do AAb employ Ig genes in a restricted manner and are there unique Ig genes different from the germline pool used in the response to exogenous antigens? To what extent is self-specificity germline encoded or acquired during B-cell development?