B cells were first implicated in lupus pathogenesis because of their roles as autoantibody producers. B cells, which play important roles in (auto)immune recognition, are now understood to also have other functional capabilities that contribute to the recruitment and stimulation of T lymphocytes and cells of the innate immune system. Herein, these emerging insights are discussed as well as the newly recognized influence on B cells of the Toll-like receptors, which are postulated to be important sources of costimulation for autoreactive B cells. Also discussed is how B-cell survival factors may contribute to the loss of immune tolerance that leads to pathologic autoimmunity. These findings are part of the rationale for the development of new specific B-cell-targeted therapies.