HSPA13 and systemic lupus erythematosus: To examine the potential role of Hspa13 in regulating IL‐10‐producing Breg function and lupus disease progression in MRL/lpr mice, we used a previously established CD19creHspa13fl/fl mouse line with Hspa13 deletion in B cells.[26] We identified Hspa13 as a novel positive regulator of IL‐10‐producing Bregs and found that it was mostly enriched in the marginal zone (MZ) B cells.