IgE receptors expressed on antigen presenting cells have been shown to facilitate the presentation of allergens in the presence of specific IgE, resulting in effective T cell activation at low allergen concentrations. It has been demonstrated with this assay that formation of allergen-IgE complexes increases with IgE clonality and allergen affinity. Interference with these IgE-dependent mechanisms by ‘blocking’ IgG antibodies may down regulate T cell responses and manifest as a reduction in allergic responses and long-term clinical tolerance.

The IgE-FAB assay represents an in vitro model of facilitated allergen presentation. Allergen-IgE complexes are incubated with an EBV-transformed B cell line and complexes bound to CD23 on the surface of cells are detected by flow cytometry.