Figure 5.

Overview of potential roles of IgE in asthma pathology (adapted and modified from).³⁶

Part 1: The IgE molecule is able to transcytosis across the epithelial cells. This process is mediated by the low-affinity FcεRII receptor expressed on the epithelial cells in the proximity of the basement membrane.

Part 2: The complexes of IgE molecule with allergen bind to the FcεRI receptor on the surface of the projections of dendritic cells that penetrate from subepithelial spaces up to the airway lumen.

Part 3: The presence of FcεRI on the surface of dendritic cells is strengthening the processes of antigen presentation to naïve Th-lymphocytes (with their subsequent maturation towards the Th2 subset), up to 1000 times.

Part 4: The key elements for the further course of allergic reaction mediated by IgE immunoglobulins are basophils and mastocytes that express large amounts of FcεRI on their surface. In the case interaction of the variable part of IgE with a soluble allergen occurs, the activation cascade inside the cells appears and leads subsequently to the early phase of allergic reaction initiation.

Part 5: Recently, the expression of both receptor types for IgE has been discovered on the surface of smooth muscle cells in the airways. The interaction with IgE molecules leads to a proliferation of the smooth muscle cells and type I, III, VII collagen and fibronectin production during remodelling processes.

Part 6: Increased expression of FcεRI associated with elevated IgE levels has been shown also on the eosinophils of atopic patients. IgE molecules thus support their survival and inhibit their apoptosis. The complex mutual relationship between IgE molecules and eosinophils is mediated also indirectly, probably through increased production of prostaglandin D₂ (PgD₂) by activated mastocytes.