IgE responses in mouse and man and the persistence of IgE memory

• New mouse models of allergy have enabled tracking of IgE+ B cells in vivo.
• These have shed light on the generation of IgE memory.
• Some differences between human and mouse IgE+ B cell biology and memory are profound.
• These differences may provide insight into the mechanisms underlying allergy and asthma.

Rapid and robust recall or ‘memory’ responses are an essential feature of adaptive immunity. They constitute a defense against reinfection by pathogens, yet arguably do more harm than good in allergic disease. Immunoglobulin (Ig)E antibodies mediate the allergic reaction characterized by immediate hypersensitivity, a manifestation of IgE memory. The origin of IgE memory remains obscure, mainly due to the low proportion of IgE-expressing B cells in the total B cell population. The recent development of ultrasensitive methods for tracking these cells in vivo has overcome this obstacle, and their use has revealed unexpected pathways to IgE memory in the mouse. Here, we review these findings and consider their bearing on our understanding of IgE memory and allergic disease in man.