B cells as a cellular adjuvant: induction or control of T-cell immunity--or both?

Evaluation of: Reichhardt P, Dornbach B, Rong S et al. Naive B cells generate regulatory T cells in the presence of a mature immunologic synapse. Blood 110 (5), 1519-1529 (2007). Cellular adjuvants, such as dendritic cells (DCs) are in the focus of tumor immunology and immunotherapy as tools to enhance immune responses in order to control cancer. Recent observations suggest that so-called tolerogenic DCs can be employed to achieve the opposite--the control of adverse immune reactions in transplantation or autoimmunity. However, the use of DCs is limited due to their low frequency, lack of purity and expansion in cell culture. Activated B cells have previously been shown to efficiently present antigen and be expandable to almost unlimited amounts, rendering them an interesting alternative to induce antitumor immune responses. The paper under evaluation extends this concept to B cells as tolerogenic cells by providing insight in a novel mechanism--the induction of regulatory T cells.