The lupus susceptibility locus Sle1 facilitates the peripheral development and selection of anti-DNA B cells through impaired receptor editing

Systemic lupus erythematosus is characterized by the spontaneous production of IgG autoantibodies in patients and lupus-prone mice. In this study, we investigated the effect of the Sle1 lupus susceptibility locus on the peripheral development of 56R⁺ anti-DNA transgenic B cells by tracking 56R ⁺ B cells in mice without (B6.56R) or with (B6.Sle1.56R) the Sle1 locus. Compared with B6.56R mice, B6.Sle1.56R mice exhibited increased class-switched IgG2a anti-DNA Abs in their serum, encoded by the transgene. Interestingly, within the spleen, Sle1 facilitated the development of these cells into clusters of IgG2a class-switched B cells juxtaposed to CD4 ⁺ T cells within extrafollicular sites. Through sequence analysis of B cell hybridomas, we also found that B cells from B6.Sle1.56R mice are inefficient at Ig H and L chain editing. Thus, the Ig H chains in Sle1.56R ⁺ B cells are partnered more often with cationic L chains that facilitate DNA binding. Taken together, these findings indicate that the Sle1 lupussusceptibility locus may facilitate the emergence of anti-DNA B cells by subduing BCR revision and possibly by shaping the extrafollicular development of effector B cells, although the precise molecular mechanisms await further study.