MS4A2 and Allergy: Fc receptors play major roles in adaptive immunity by interacting with immunoglobulins, among which FcεRI represents a high-affinity IgE receptor found on mast cells, basophils, eosinophils and APCs.309 When IgE binds to FcεRI to trigger immunity, FcεRI aggregation induces a variety of signaling pathways to regulate the secretion of allergy-associated mediators, including histamines and leukotrienes, and induces the transcription of Th2 cytokines and tumor necrosis factor (TNF) genes,310 which leads to potentially life-threatening allergic diseases.