Regulatory B cells induce formation of IL-10-expressing T cells in mice with autoimmune neuroinflammation

Although B cells are traditionally known for their role in propagating proinflammatory immune responses, their immunosuppressive effects have only recently begun to be appreciated. How these regulatory B cells (B_regs) suppress the immune response remains to be worked out in detail. In this article, we show that B_regs can induce the formation of conventional FoxP3⁺regulatory T cells (T_regs), as well as a more recently described CD49b⁺CD223⁺ regulatory T-cell subset, known as type 1 regulatory T cells (Tr1s). When Bregs are transferred into mice with experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis, they home to the spleen and mesenteric lymph nodes, leading to an expansion of T_regs and Tr1 in vivo. T_regs and Tr1s are also found in greater proportions in the CNS of mice with EAE treated with B_regs and are correlated with the remission of symptoms. The discovery that B_regs induce the formation of regulatory T-cell subsets in vivo may herald their use as immunosuppressive agents in adoptive cellular therapies for autoimmune pathologies.