BCR analysis of single-sorted, putative IgE+ memory B cells in food allergy: an ephemeral existence?

Immunoglobulin ( Ig) E is the critical effector molecule in allergic reactions. Consequently, research efforts to understand the biology of IgE-expressing cells is of paramount importance. In particular, the role of IgE+ memory B cells(MBCs) in the perpetuation of allergic reactivity has been the subject of intense research. Studies in mice have convincingly established that IgE+ B cells are rare and transient and, therefore, an unlikely candidate to maintain allergic disease. In contrast, IgE+ MBCs have been detected by flow cytometryin the sputum and peripheral blood of humans and have been proposed as a clinical marker of allergic disease. We established a method to genetically validate, at the single-cell level, the putative IgE+ MBCs identified by flow cytometryfrom humans. We, then used this information to develop an enhanced flow cytometryprotocol that more accurately identifies bona fide IgE+ MBCs. We found that IgE+ MBCs were detected in some patients with atopic dermatitis, but at a frequency that was ~100 times lower than previously reported. We also found that IgE+ MBCs were undetectable in PBMCs from peanut allergic patients. These findings provide tools to identify bona fide IgE+ MBCs, demonstrate their extreme rarity in circulation and are consistent with the lack of a central role for IgE+ MBCs in the maintenance of allergic sensitivity.