Figure 4.

Notch expression and role in B cell differentiation. Expression of Notch receptors and ligands (red text) on bone marrow B cell progenitors and peripheral B cell subsets. Notch signaling is thought to be involved in self-renewal of hematopoietic stem cells (HSCs). The differentiation of early progenitor cells to pro-B cells is inhibited by ectopic Notch signaling, though evidence is still lacking that endogenous Notch signaling controls this step. Some evidence suggests that Notch2 activation may regulate commitment to the B-1 subset, but this pathway is still controversial since there are contradictory findings in different studies. In the periphery, Notch2 signaling is required for specification of marginal zone (MZ) B cells, while it inhibits formation of follicular (FO) B cells. Notch signaling also stimulates the differentiation of mature B cells into antibody-secreting cells (ASCs).