Adoptive Transfer of Tumor Reactive B Cells Confers Host T-Cell Immunity and Tumor Regression

Abstract

We investigated the antitumor reactivity of adoptively transferred effector B cells and the mechanisms by which they may mediate tumor regression in a spontaneous metastases model. 4T1 breast cancer cells were inoculated into the flanks of syngeneic Balb/C mice to prime draining lymph nodes. Tumor-draining lymph nodes (TDLN) were harvested and B cells activated ex vivo with lipopolysaccharide and anti-CD40 monoclonal antibody. These activated B cells were adoptively transferred into mice inoculated with 4T1 tumor in the mammary fat pad. The induction of host T-cell immunity was evaluated. Activated 4T1 TDLN B cells secreted immunoglobulin G (IgG) in response to tumor cells which was immunologically specific. These activated B cells were capable of mediating specific lysis of tumor cells in vitro. Transfer of these activated B cells alone mediated the inhibition of spontaneous metastases to the lung. Examination of the host revealed that the transfer of these B cells resulted in the induction of tumor-specific T-cell immunity as measured by cytotoxicity and cytokine (IFNγ and granulocyte-macrophage colony-stimulating factor) production. The combined transfer of activated T and B cells from TDLN resulted in tumor regression, which was greater than either cell population alone, with host B cells capable of producing IgG that mediated lysis of tumor in the presence of complement. We have found that appropriately primed B cells can mediate tumor regression by itself and confers host T-cell antitumor immunity. Furthermore, effector B cells can serve as a useful adjunct in adoptive T-cell therapy.