Clinical Implications of Basic Science Discoveries: Janus Resurrected-Two Faces of B Cell and Plasma Cell Biology

B cells play a complex role in the immune response. In addition to giving rise to plasma cells (PCs) and promoting T cell responses via antigen presentation, they perform immunoregulatory functions. This knowledge has created concerns regarding nonspecific B cell depletional therapy because of the potential to paradoxically augment immune responses. Recent studies now indicate that PCs have immune functions beyond immunoglobulin synthesis. Evidence for a new role for PCs as potent regulatory cells (via IL-10 and IL-35 production) is discussed including the implications for PC-targeted therapies currently being developed for clinical transplantation. In this new feature, the authors discuss the recent article IL-35-producing B cells are critical regulators of immunity during autoimmune and infectious diseases (Nature 2014; 507: 366-370) and its implications for transplantation.