Transcription factor c-Maf is essential for IL-10 gene expression in B cells

Interleukin (IL)-10 is an essential anti-inflammatory cytokine that plays important roles as a negative regulator of immune responses to microbial antigens. c-Maf has been suggested as an essential transcriptional factor for IL-10 production in CD4⁺ T cells and macrophages. However, it remains unclear whether c-Maf participates in IL-10 expression in B cells. In this study, we investigated the role of c-Maf in the transcriptional regulation of IL-10 in regulatory B cells, as well as the underlying molecular mechanism. We found that c-Maf was constitutively expressed in resting B cells. c-Maf expression was upregulated in the presence of LPS and dose-dependently enhanced IL-10 production following binding to the IL-10 promoter. Moreover, a lower expression of c-Maf and decreased production of regulatory B (Breg) cells were detected in mice with collagen-induced arthritis (CIA), which may contribute to the pathological changes. Taken together, these data demonstrate that c-Maf is an indispensable yet constitutive transcription factor for IL-10 gene expression in LPS-activated B cells.