IgEmemedieerde

IgE-mediated, also described as type I hypersensitivity, is an immune mechanism underlying many common allergic reactions. It involves immunoglobulin E (IgE) antibodies that specifically recognize harmless environmental allergens such as pollen, foods, or insect venom.

Mechanism: On first exposure, helper T cells release cytokines such as IL-4 and IL-13, which promote class switching of B cells to produce IgE. The resulting IgE antibodies bind to high-affinity FcεRI receptors on mast cells and basophils, sensitizing them. When the allergen is encountered again, it cross-links the bound IgE, triggering degranulation of mast cells and basophils and release of mediators such as histamine, tryptase, leukotrienes, and prostaglandins. These mediators cause vasodilation, increased vascular permeability, smooth muscle contraction, mucus production, and itching.

Clinical features: Reactions typically occur within minutes of exposure and can affect multiple organ systems. Common manifestations include nasal congestion and itching, sneezing, conjunctival irritation, urticaria or angioedema, bronchospasm, and, in severe cases, anaphylaxis.

Diagnosis: Diagnosis relies on clinical history and objective testing. Skin prick tests or serum-specific IgE tests identify sensitization to particular allergens. Basophil activation tests and compilation of reaction patterns may support complex cases. Diagnosis often distinguishes IgE-mediated allergies from non-IgE-mediated inflammatory responses.

Management: Primary strategies include avoidance of known allergens and appropriate pharmacotherapy. Antihistamines, nasal or airway corticosteroids, and leukotriene receptor antagonists are commonly used, with epinephrine as first-line treatment for anaphylaxis. Allergen immunotherapy (subcutaneous or sublingual) can reduce sensitivity for certain allergens over time.

Prognosis and epidemiology: IgE-mediated allergies are common and can begin in childhood or adulthood. Some allergies wane over time, particularly in children, while others persist. Ongoing management aims to reduce symptoms and the risk of severe reactions.