Activation of Human Peripheral Basophils in Response to High IgE Antibody Concentrations without Antigens

Basophils and mast cells have high affinity IgE receptors (Fc epsilon RI) on their plasma membrane and play important roles in Fc epsilon RI-associated allergic diseases, such as pollen allergy, food allergy, chronic spontaneous urticarial (CSU), and atopic dermatitis (AD). To date, several reports have revealed that high IgE antibody concentrations activate mast cells-which reside in tissue-in the absence of any antigens (allergens). However, IgE antibody-induced activation of basophils-which circulate in blood-has not been reported. Here, we investigated whether IgE antibodies may regulate functions of human peripheral basophils without antigens in vitro. We successfully removed IgE antibodies bound to Fc epsilon RI on the surface of human peripheral basophils by treating with 0.1% lactic acid. We also demonstrated that high IgE antibody concentrations (>1 mu M) induced histamine release, polarization, and CD203c upregulation of IgE antibody-stripped basophils. Thus, high IgE antibody concentrations directly activate basophils, which express IgE-free Fc epsilon RI on the cell surface. This mechanism may contribute to the pathogenesis of patients with AD and CSU who have higher serum IgE concentrations compared to healthy donors.