Notch2 signaling guides B cells away from germinal centers towards marginal zone B cell and plasma cell differentiation

Abstract Notch2 signaling has a profound role in driving the development of Marginal Zone B (MZB) cells. We recently demonstrated that Follicular B (FoB) cells act as precursors for MZB cells in mice, but the mechanistic aspects of this differentiation pathway are still elusive. By studying Notch signaling in CBF:H2B-Venus Notch-reporter mice, we show that most B cells receive a Notch signal, which is highest in MZB cells. However, surprisingly, around one-third of MZB cells seem to lose their Notch signal with time. Conditional deletion or constitutive activation of Notch2 in mice upon T-cell-dependent (TD) immunization unraveled an interplay between antigen-induced activation and Notch2 signaling, in which FoB cells that turn off the Notch pathway enter germinal centers, whereas FoB cells with high Notch signals undergo MZB cell or plasmablast differentiation. Input of experimental data into a mathematical modeling framework reveals that MZB cells regularly emerge from antigen-activated FoB cells in a Notch2-dependent manner upon TD immunization.