Role of Der p 1–specific B cells in immune tolerance during 2 years of house dust mite–specific immunotherapy

Long-term follow-up of allergen-specific B cells in terms of immunoglobulin isotype expression, plasmablast differentiation, and regulatory B (Breg) cell development during allergen-specific immunotherapy (AIT) has not been reported. Allergen-specific B-cell responses during 2 years of house dust mite AIT were compared between responder and nonresponder patients. B cells specific for Der p 1 were detected by using the fluorochrome-labeled allergen method. The frequency of IgA-, IgG1- and IgG4-switched Der p 1–specific B cells, plasmablasts, and IL-10– and IL-1 receptor antagonist (IL-1RA)–producing Breg cells were investigated and correlated to clinical response to AIT. Sixteen of 25 patients completed the 2-year study. Eleven responder patients showed a successful response to AIT, as measured by a decrease in symptom-medication scores from 13.23 ± 0.28 to 2.45 ± 0.24 (P = .001) and a decrease in skin prick test reactivity to house dust mite from 7.0 ± 1.3 to 2.7 ± 0.5 mm (P = .001). IgG4+ and IgA+ Der p 1–specific B cells showed a significant increase after AIT, with a significantly greater frequency in responders compared with nonresponders in the IgG4+ but not the IgA+ fraction. The frequency of plasmablasts and IL-10– and/or IL-1RA–producing Breg cells was greater among responders compared with nonresponders after 2 years. The increased frequency of Der p 1–specific IgG4+ B cells, plasmablasts, and IL-10+ and dual-positive IL-10+IL-1RA+ Breg cells significantly correlated with improved clinical symptoms over the course of AIT. Allergen-specific B cells in patients responding to AIT are characterized by increased numbers of IgA- and IgG4-expressing Der p 1–specific B cells, plasmablasts, and IL-10+ and/or IL-1RA+ Breg cells. [Display omitted]