Suppression of autoimmunity by CD5 + IL-10-producing B cells in lupus-prone mice

Systemic lupus erythematosus is a complex autoimmune disorder characterized by the production of pathogenic anti-nuclear antibodies. Previous work from our laboratory has shown that the introgression of a New Zealand Black-derived chromosome 4 interval onto a lupus-prone background suppresses the disease. Interestingly, the same genetic interval promoted the expansion of both Natural Killer T- and CD5+ B cells in suppressed mice. In this study, we show that ablation of NKT cells with a CD1d knockout had no impact on either the suppression of lupus or the expansion of CD5+ B cells. On the other hand, suppressed mice had an expanded population of IL-10-producing B cells that predominantly localized to the CD5+CD1dlow compartment. The expansion of CD5+ B cells negatively correlated with the frequency of pro-inflammatory IL-17 A-producing T-cells and kidney damage. Adoptive transfer with a single injection of total B cells with an enriched CD5+ compartment reduced the frequency of memory/activated, IFNγ-producing, and IL-17 A-producing CD4 T-cells but did not significantly reduce autoantibody levels. Taken together, these data suggest that the expansion of CD5+ IL-10-producing B cells and not NKT cells protects against lupus in these mice, by limiting the expansion of pro-inflammatory IL-17 A- and IFNγ-producing CD4 T-cells.