High-affinity immunoglobulin E receptor complex bound to Fel d 1-IgE (FcεRI/Fel d 1-IgE complex)

The FcεRI/Fel d 1–IgE complex is a tripartite molecular assembly central to immediate-type allergic responses. FcεRI (high-affinity IgE receptor) is a multimeric, cell surface receptor—expressed mainly on mast cells and basophils—where its extracellular α chain captures the Fc region of IgE. Fel d 1 is the dominant cat allergen, a uteroglobin-like protein, which binds to allergen-specific IgE. Upon exposure to Fel d 1, preformed Fel d 1–IgE complexes cross-link FcεRI on sensitized effector cells, inducing rapid degranulation and inflammatory mediator release, the hallmark of allergic inflammation. This molecular complex is the principal driver of cat-induced allergy and serves as a key target for both biologic therapies (e.g., anti-IgE antibodies, Fel d 1-blocking antibodies) and diagnostic approaches in allergy medicine. Targeting the interactions within this complex has been at the heart of recent advances in allergen-specific immunotherapy and biologics for allergy and asthma. The term "FcεRI/Fel d 1-IgE complex" is not a standard single receptor or protein but denotes the pathophysiologically critical molecular assembly for cat allergy and allergic asthma research and therapy. The canonical targets are usually defined separately: "High-affinity immunoglobulin E receptor" (FcεRI) and "Fel d 1" (cat allergen). The complex is of direct therapeutic interest because it is where inhibition can block allergic inflammation at the effector stage.

Other names

FcεRI-IgE-Fel d 1 complexIgE–FcεRI–Fel d 1 complexCat allergen–IgE–FcεRI complexHigh-affinity IgE receptor–Fel d 1–IgE complex

IgE binding blockade: Prevent binding of IgE to FcεRI or to Fel d 1, inhibiting receptor cross-linking and cell activation. Allergen neutralization: Fel d 1-specific IgG antibodies outcompete IgE, thus blocking the pathway and preventing mast cell activation. Desensitization: Immunotherapy aims to induce tolerance by gradual exposure to Fel d 1 epitopes.