Cutting Edge: Importance of IL-6 and cooperation between innate and adaptive immune receptors in cellular vaccination with B lymphocytes.

B lymphocytes are a potential alternative to dendritic cell immunotherapy, with the advantages of relative abundance in peripheral blood and the ability to function as APCs. Although B cells express multiple receptors that induce costimulatory molecules, B cell vaccine studies have focused primarily on CD40 stimulation. To optimize the potential efficacy of B cell vaccines (Bvac), we compared the capacity of differentially stimulated B cells to induce Ag-specific CD8(+) T cell responses in vivo. CD40- or TLR7-stimulated B cell APCs induced similar CD8(+) T cell responses, but costimulation through the BCR and TLR7 produced a more effective Bvac as measured by T cell stimulation and the protection of mice from an infectious pathogen. This increased effectiveness depended upon enhanced production of IL-6 by BCR plus TLR7-stimulated B cells. These findings reveal alternative stimulation strategies for the production of effective Bvac and identify a key role for IL-6 in B cell Ag presentation and cellular vaccines.