RIAKEY Total IgE IRMA Tube is an immunoradiometric assay on coated tubes for the IN VITRO determination of total IgE in human serum.
The immunoglobulins E (IgE) which were first isolated in 1968 by Bennich and Johansson in Uppsala, are the fifth class of immunoglobulins. The monomer for IgE is formed by two light chains linked by sulfide bridges, and two heavy chains able to fix the complement. The IgE have a molecular weight ranging from 188 to 196 kDa. They consist of 12% carbohydrates and have a sedimentation constant of 7.925S. The reaginic activity of IgE is due to the remarkable affinity of the e chains with specific receptors which are present on the membrane of mast cells as well as polynucleotide basophils. The release of pharmacological mediators (ex. histamine) is caused by the interaction between IgE (bound to membrane receptors) and inhaled or adsorbed allergens. In atopic subjects (high IgE concentration) the receptor sites are 100% saturated. In non-atopic subjects (low IgE concentration) the maximum saturation reaches 20%. In normal subjects, IgE concentration is extremely low. In subjects with allergic pathologies (asthma, hay fever, eczemas) IgE concentrations are high.
IgE concentration is correlated with the degree of immunostimulation. The more allergens there are, to which the patient is allergic and exposed, the more serious the symptoms will be, and the higher will be the IgE level. The IgE concentration may be affected by circadian variations. In addition, they vary considerably from person to person. IgE levels tend to increase from the time of birth up to 60-65 years of age, after which they may decrease. Low levels of IgE do not always exclude an allergic etiology. In fact, univalent allergies (sensitivity to a single allergen) are at times characterized by low IgE levels. In such cases, the diagnosis can be done only by highly sensitive tests for specific IgE.
The present method employs two anti-IgE monoclonal antibodies which recognize two different epitopes of the molecule. One antibody is adsorbed in solid phase (coated tube), the other (labeled with iodine-125) is used as conjugate. The sample to be tested and the labeled antibody are incubated simultaneously in the coated tube. The amount of bound conjugate will thus be directly proportional to the antigen concentration in calibrators and samples. At the end of the incubation, the unbound material is removed by aspiration and washing. The radioactivity in the tubes is measured in a gamma counter.