In vitro effects of adjuvants on B cells

Stimulation of B cells not only through the B cell antigen receptor (BCR) but also through Toll-like receptors (TLRs) can drive activation, proliferation, and differentiation of B cells to result in antigen-specific antibody secretion. In addition, B cells are co-stimulated by specific antigen and the presence of a TLR ligand such as for TLR9, which selectively enhances the development of antigen-specific antibodies and endows B cells with strong antigen-presenting capabilities to T cells. These effects promote antigen-specific immune responses and account for the strong adjuvant effect of TLR9 ligands. Several studies have described the activation of human or murine B cells by TLR ligands or other adjuvants. However, there are no reports summarizing the various different effects adjuvants can have on B cells, nor how to best measure these effects. Here, we will try to give an overview on the TLR expression pattern of human, primate, and murine B cells, their stimulation by TLR ligands or other adjuvants, and the outcome such as B cell proliferation and cytokine production.