Allergen-specific immunoglobulin E bound to high-affinity IgE receptor (FcεRI) on mast cell (Allergen-specific IgE–FcεRI complex)

Allergen-specific IgE on mast cells refers to IgE antibodies that are specific for particular environmental antigens (“allergens”) and are bound via their Fc region to high-affinity FcεRI receptors on the surface of mast cells. Once an individual is sensitized to an allergen, B cells are induced under T-helper 2 cytokine influence to produce IgE specific for that allergen. The Fc region of these IgE molecules binds tightly to FcεRI on mast cells (and basophils), where it can remain for weeks or months. On subsequent exposure to the same allergen, the allergen cross-links these cell-bound specific IgE molecules, provoking aggregation of FcεRI. This initiates a signaling cascade (involving Src-family kinases, Syk, and adaptor proteins) that results in rapid degranulation and the release of histamine, prostaglandins, leukotrienes, and cytokines. These mediators produce the classic symptoms of allergic reactions and, if systemic, can cause anaphylaxis[1][2][3][5][6][8][9]. Therapies such as omalizumab target this pathway by neutralizing free IgE, preventing it from binding to FcεRI, thereby reducing mast cell activation and the propensity for allergic reactions. This molecular complex is thus central to the pathogenesis of allergic diseases and is a validated target for anti-allergic therapies.

Other names

IgE–FcεRI complexMast cell-bound allergen-specific IgESurface-bound IgE (on mast cells)Mast cell IgE receptor complex

Blocking IgE binding to FcεRI to prevent complex formation and mast cell sensitization (e.g., omalizumab prevents free IgE from binding FcεRI, leading to downregulation of FcεRI on mast cells). Disruption of IgE–FcεRI cross-linking, thus preventing degranulation and mediator release.