Fluorescent In Vivo Detection Reveals that IgE+ B Cells Are Restrained by an Intrinsic Cell Fate Predisposition

SummaryIgE antibodies may be protective in parasite immunity, but their aberrant production can lead to allergic disease and life-threatening anaphylaxis. Despite the importance of IgE regulation, few studies have directly examined the B cells that express IgE, because these cells are rare and difficult to detect. Here, we describe fluorescent IgE reporter mice and validate a flow cytometry procedure to allow sensitive and specific identification of IgE-expressing B cells in vivo. Similar to IgG1+ cells, IgE+ B cells differentiated into germinal center (GC) B cells and plasma cells (PCs) during primary immune responses to a T cell-dependent hapten-protein conjugate and the helminth Nippostrongylus brasiliensis. However, the participation of IgE+ B cells in GCs was transient. IgE+ B cells had an atypical propensity to upregulate the transcription factor Blimp-1 and undergo PC differentiation. Most IgE+ PCs were short lived and showed reduced affinity maturation, revealing intrinsic mechanisms that restrict the IgE antibody response