Figure 2. B cells as positive mediators of the antitumor response.
B cells can produce lymphotoxin, which has an additional role of promoting the formation of tertiary lymphoid organs, which is positively correlated with disease outcome and patient survival. The production of antibodies by plasma cells has many roles in contributing to the antitumor response: antitumor antibodies promote antibody- and complement-mediated killing of the tumor cells, Fc-mediated phagocytosis by macrophages, and antibody-dependent cell-mediated cytotoxicity (ADCC) by natural killer (NK) cells. Importantly, antibody-coated tumor cells can also be taken up and processed by dendritic cells, which present tumor antigens to CD4+ T cells and cross-present antigens to CD8+ T cells. If the tumor antigen contains an MHC-I epitope, anti-tumor CD8+ T cells could be activated; these effector CD8+ cytotoxic T cells will then traffic to the site of the tumor, killing the tumor cells. In some cases, B cells can also take up and process tumor antigens, which can then be presented to CD4+ T cells.