An Increase of B Cells in the Tumor-Bearing State has the Potential to Induce Anti-Tumor Immunity

Abstract

We investigated the role of an increased amount of B cells in the tumor-bearing state. The proportion of B cells increased concomitantly with tumor development in the regional lymph nodes (LN) of BALB/c mice bearing Meth A fibrosarcoma (Meth A). Tumor development was accompanied by an increased level of IgG antibodies against Meth A. CD4 + T cells of the regional LN in the early tumor-bearing stage produced significant levels of interferon-μ and interleukin-4 in response to in vitro stimulation with coated anti-CD3 monoclonal antibody, whereas such capacities decreased in the late tumorbearing stage. In a tumor-neutralizing assay, the growth of Meth A was significantly suppressed by a co-inoculation with splenic B cells from BALB/c mice in the late tumorbearing state. This suppression of Meth A growth was tumor-specific and was abolished by the in vivo depletion of either CD4 + or CD8 + T cells. These findings thus suggest that tumor development was accompanied by an increase of B cells and tumor-specific IgG production, but such kinetic changes were not the result of a preferential activation of Th2 type CD4 + T cells. Furthermore, our results indicate that the increase of B cells in the tumor-bearing state has the potential to induce anti-tumor-specific T cell immunity.