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 B regs 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. SIGNIFICANCE STATEMENT 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 regulatory B cells (B regs ) suppress the immune response remains to be fully understood. In this article, we show that B regs can induce the formation of conventional regulatory T cells (T regs ) as well as type 1 regulatory T cells (Tr1s). When B regs are transferred into mice with experimental autoimmune encephalomyelitis (EAE), they home to secondary lymphoid organs, leading to an expansion of T regs and Tr1s 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.