A critical role for B cells in cancer immune surveillance

It is commonly believed that B cells play no role in cancer immune surveillance. However, this conclusion is based on studies using only a single B cell-deficient mouse strain, muMT mice, which does not show increased tumorigenesis compared with wild-type (WT) mice. In this study, we demonstrate a critical role for B cells in anti-tumor immunity and identify the cellular mechanisms that make muMT mice a special case. First, we replicate previous findings using a melanoma model in muMT mice. Then, we show that in muMT mice, B-cell deficiency is compensated for by a significant increase in another potent anti-tumor cell type, Type-1 interferon (IFN I)-producing plasmacytoid DCs (pDCs), resulting in normative anti-tumor responses. Depleting pDCs in muMT mice resulted in a significant increase in tumor size and burden. Conversely, adoptive transfer of antibodies from naive WT serum into pDC-depleted muMT mice significantly decreased the tumor load to WT levels. Additionally, a B cell antibody repertoire-deficient mouse strain, IghelMD4 mice, showed a 3-fold increase in tumors relative to WT mice. Overall, these findings indicate the need for a diverse antibody repertoire for early neoplastic cell recognition and the critical role B cells play in anti-cancer immunity.