B cell responses to CD40 stimulation ignite anti-tumor immunity by activating CD8⁺ T cell cytotoxicity

B cell responses to cancer are critical to patient survival and response to therapy. Yet, the knowledge as to how B cells can elicit anti-tumor immunity remains incomplete. We identify that CD40 pathway activation in B cells in the presence of high tumor mutation burdens activates an anti-tumor B cell response. Significantly, our study shows that CD40-stimulated B cells drive tumor infiltration, organization, and activation of cytotoxic function in CD8⁺ T cells. These results provide key advances in the mechanistic regulation and function of B cell and CD8⁺ T cell responses to cancer.