We investigated the role of MrgprB2+ versus MrgprB2neg MC populations by assessing Mrgprb2-Cre+; iDTRfl/fl mice versus littermate controls in a model of IgE-dependent passive systemic anaphylaxis (Fig. 4E) and in a more physiological model of active peanut-induced food allergy over a period of 28 d (Fig. 4 F). The gene discussed is IGHE; the disease is food allergy.