IgE plus B cells are scarce, but allergen-specific B cells with a memory phenotype circulate in patients with allergic rhinitis

Background: Despite the critical role of immunoglobulin E (IgE) in allergy, circulating IgE+ B cells are scarce. Here, we describe in patients with allergic rhinitis B cells with a memory phenotype responding to a prototypic aeroallergen. Methods: Fifteen allergic rhinitis patients with grass pollen allergy and 13 control subjects were examined. Blood mononuclear cells stained with carboxyfiuorescein diacetate succinimidyl ester (CFSE) were cultured with Bahia grass pollen. Proliferation and phenotype were assessed by multicolour flow cytometry. Results: In blood of allergic rhinitis patients with high serum IgE to grass pollen, most IgE(hi) cells were CD123+ HLA-DR- basophils, with IgE for the major pollen allergen (Pas n 1). Both B and T cells from pollen-allergic donors showed higher proliferation to grass pollen than nonallergic donors (P = 0.002, and 0.010, respectively), whereas responses to vaccine antigens and mitogen did not differ between groups. Allergen-driven B cells that divided rapidly (CD19(mid) CD3(-) CFSElo) showed higher CD27 (P = 0.008) and lower CD19 (P = 0.004) and CD20 (P = 0.004) expression than B cells that were slow to respond to allergen (CD19(hi) CD3(-) CFSEmid). Moreover, rapidly dividing allergen-driven B cells (CD19(mid) CFSElo CD27(hi)) showed higher expression of the plasmablast marker CD38 compared with B cells (CD19(hi) CFSEmid CD27(lo)) that were slow to divide. Conclusion: Patients with pollen allergy but not control donors have a population of circulating allergen-specific B cells with the phenotype and functional properties of adaptive memory B-cell responses. These cells could provide precursors for allergen-specific IgE production upon allergen re-exposure.