The roles of B1 and marginal zone B cells in autoimmunity; The role of the recently discovered B10 cell population in autoimmunity; The survival/apoptotic pathways that when dysregulated lead to expansion and survival of autoreactive B cells (such as the BAFF/BlyS receptor system and CD40); Tolerance checkpoint mechanisms regulating the formation of high affinity autoreactive B2 cells both in and outside the germinal center; Environmental agents with the potential to disrupt B cell function. The gene discussed is CD40; the disease is Autoimmunity.