Type I interferons provide additive signals for murine regulatory B cell induction by Schistosoma mansoni eggs

The helminth Schistosoma mansoni (S. mansoni) induces a network of regulatory immune cells, including interleukin (IL)‐10‐producing regulatory B cells (Bregs). However, the signals required for the development and activation of Bregs are not well characterized. Recent reports suggest that helminths induce type I interferons (IFN‐I), and that IFN‐I drive the development of Bregs in humans. We therefore assessed the role of IFN‐I in the induction of Bregs by S. mansoni. Mice chronically infected with S. mansoni or i.v. injected with S. mansoni soluble egg antigen (SEA) developed a systemic IFN‐I signature. Recombinant IFN‐α enhanced IL‐10 production by Bregs stimulated with S. mansoni SEA in vitro, while not activating Bregs by itself. IFN‐I signaling also supported ex vivo IL‐10 production by SEA‐primed Bregs but was dispensable for activation of S. mansoni egg‐induced Bregs in vivo. These data indicate that although IFN‐I can serve as a coactivator for Breg IL‐10 production, they are unlikely to participate in the development of Bregs in response to S. mansoni eggs.