Li et al. investigated the therapeutic efficacy of in vivo tumor-primed and ex vivo activated B-cells to mediate breast cancer regression: in murine 4TI breast cancer models, the adoptive transfer of effector B-cells from tumor-draining lymph nodes (TDLN) further activated with LPS and anti-CD40 mAb resulted in increased IgG secretion, inhibition of spontaneous metastases to the lung and tumor-specific T cell immunity. Here, CD40 is linked to breast cancer.