IgE antibody in the serum – detection and diagnostic significance

Allergy Review Series X: Progress in diagnosis of allergy in vitro IgE antibody in the serum -detection and diagnostic significanceNormally, immunoglobulin E (IgE) is a tissue-bound molecule.It is present in the serum in only nanogram amounts, in equilibrium with that bound to mast cells, basophils, and other cells.The subject of study for many years before its description, IgE was termed a ÔreaginÕ because it shared the heat-lability of the complement proteins.Johansson's discovery of an untypable myeloma protein, initially termed IgND, in the serum of a Swedish farmer permitted separation of relatively large amounts of the protein and preparation of rabbit antisera for use in immunoassay (1).Confirmation that IgND was identical to the cE discovered by Ishizaka and Ishizaka (2) and that both were the elusive reagin of immediate hypersensitivity reactions quickly resulted in design and commercialization of immunoassays for allergen-specific IgE.The early Phadebas RAST (RadioAllergoSorbent Test, Pharmacia, Uppsala, Sweden) has been made obsolete by advances in assay technology.While the term ÔRASTÕ is often used colloquially to describe any immunoassay for allergenspecific IgE, it is best avoided because it describes a detection system now rarely used, and it is a trademark.A typical modern immunoassay uses allergenic source materials bound to a matrix.Patient serum is added.Following incubation and washing, an enzyme-labeled anti-human IgE antibody is added.After a second incubation and washing, enzyme substrate is added, response is measured, and results are calculated and reported.Most assays report quantitative results. Reagents and equipment for testing Allergenic materialsBecause they are biologic products, allergen extracts have substantial, inherent lot-to-lot and manufacturer-