Chronic calcium signaling in IgE⁺ B cells limits plasma cell differentiation and survival

In contrast to other antibody isotypes, B cells switched to IgE respond transiently and do not give rise to long-lived plasma cells (PCs) or memory B cells. To better understand IgE-BCR-mediated control of IgE responses, we developed whole-genome CRISPR screening that enabled comparison of IgE⁺ and IgG1⁺ B cell requirements for proliferation, survival, and differentiation into PCs. IgE⁺ PCs exhibited dependency on the PI3K-mTOR axis that increased protein amounts of the transcription factor IRF4. In contrast, loss of components of the calcium-calcineurin-NFAT pathway promoted IgE⁺ PC differentiation. Mice bearing a B cell-specific deletion of calcineurin B1 exhibited increased production of IgE⁺ PCs. Mechanistically, sustained elevation of intracellular calcium in IgE⁺ PCs downstream of the IgE-BCR promoted BCL2L11-dependent apoptosis. Thus, chronic calcium signaling downstream of the IgE-BCR controls the self-limiting character of IgE responses and may be relevant to the accumulation of IgE-producing cells in allergic disease.