Batf controls the global regulators of class switch recombination in both B and T cells

The transcription factor Batf controls T(H)17 differentiation by regulating the expression of both RORγt and RORγt target genes such as Il17. Here, we report the mechanism by which Batf controls in vivo class switch recombination (CSR). In T cells, Batf directly controls expression of the transcription factors Bcl-6 and c-Maf, both of which are needed for development of T follicular helper (T(FH)) cells. Restoring T(FH) activity to Batf(−/−) T cells in vivo requires co-expression of both Bcl-6 and c-Maf. In B cells, Batf directly controls the expression of both activation-induced cytidine deaminase (AID) and of I(H)-C(H) germline transcripts. Thus, Batf functions at multiple hierarchical levels across two cell types to globally regulate in vivo switched antibody responses.