High-affinity immunoglobulin epsilon receptor (FcεRI) - Immunoglobulin E (IgE) complex (FcεRI-IgE complex)

The complex formed by patient-specific Immunoglobulin E (IgE) and the high-affinity IgE receptor (FcεRI) on cutaneous mast cells is the primary mediator of allergic skin diseases and systemic hypersensitivity [1, 5]. In sensitized individuals, mast cells are primed with IgE antibodies specific to various allergens; when these allergens encounter the mast cells, they cross-link the IgE-FcεRI complexes, triggering the rapid release of inflammatory mediators like histamine, proteases, and cytokines [5, 9]. This degranulation leads to the clinical manifestations of allergy, such as wheals, itching, and inflammation in chronic spontaneous urticaria (CSU) [2, 4]. Therapeutic interventions like omalizumab work by binding to free IgE, which shifts the equilibrium to promote the dissociation of the complex and subsequent down-regulation of the receptor on the cell surface [1, 4]. Emerging therapies, such as disruptive DARPins (e.g., E2_79), aim to directly dissociate the pre-formed IgE-FcεRI interaction to provide more rapid desensitization [6, 7].

Other names

Mast cell-bound IgEIgE-FcεRI complexHigh-affinity IgE receptor complexSurface-bound IgE

Drugs targeting this complex primarily work by sequestering free IgE (e.g., omalizumab, ligelizumab), which prevents new IgE-FcεRI complexes from forming and leads to the gradual dissociation and internalization of existing surface receptors [1, 5]. Newer experimental agents, such as disruptive DARPins or allosteric antibodies, are designed to actively dissociate pre-bound IgE from the FcεRI receptor, offering a more direct and rapid reduction in mast cell sensitivity [6, 7]. Additionally, downstream signaling inhibitors like BTK inhibitors (e.g., remibrutinib) block the activation signals generated by the complex upon allergen cross-linking [9].