B cells can contribute to immunity through production of antibodies, presentation of antigen to T cells, and secretion of cytokines. Through these mechanisms, B cells can act both as drivers and as regulators of immunity, and these two antagonistic activities seem to be at play during the majority of immune responses. Understanding how these opposite functions are mediated shall stimulate the elaboration of novel approaches for monitoring and manipulating the immune system. Here, we will discuss specifically about how B cells negatively regulate immunity through provision of cytokines. The presentation will discuss the suppressive roles of B cells during autoimmune disorders, and infectious diseases. The signals controlling the acquisition of suppressive functions by B cells (BCR, TLR, CD40), the mediators of suppression (production of IL-10 and IL-35), and the mechanisms of suppression (effects on innate cells, effector and regulatory T cells) will be presented. Moreover, we will discuss the phenotype of the B cells providing these regulatory functions in vivo, emphasizing the concept that specific subsets of plasma cells/plasmablasts are the major B cell source of regulatory IL-10 and IL-35 in vivo.
Disclosure of Interest None declared