B Cells in Cancer Immunology: For or Against Cancer Growth?

The role played by B cells in cancer immunology is complex and somewhat controversial. Depending upon their state of activation, B cells have had divergent roles in T cell differentiation and effector function. Over the years, the role of B cells in the host immune response to malignancy has been overshadowed by our focus on T cells and remains to be fully defined. While studies on B cells in immune responses have been focused on antigen presentation and antibody production, it has recently been found that primed and activated B cells can function as effector cells to mediate tumor destruction. At the same time, newly identified B cell subsets can function as regulatory cells to inhibit antitumor immunity. CD40-activated B (CD40-B) cells represent a promising alternative to dendritic cells as antigen-presenting cells. B cells could potentially have direct cytotoxicity against tumor cells. Furthermore, tumor-infiltrating B cells (TIL-Bs) have been found to correlate with favorable survival of cancer patients. In contrast, regulatory B cells (Bregs) have been identified which downregulate antitumor immunity. This chapter is intended to review these respective aspects of B cells which are involved in the host response to tumor.