Immunoglobulin E (IgE) is an antibody isotypes, found only in mammals. Although IgE is typically the least abundant isotype - blood serum IgE levels in a normal ("non-atopic") individual are ~150ng/ml, compared to 10mg/ml for the IgGs (the isotypes responsible for most of the classical adaptive immune response) - it is capable of triggering the most powerful immune reactions. Most of our knowledge of IgE has come from an allergy known as type 1 hypersensitivity.
IgE plays an important role in allergy, and in the immune system?s recognition of cancer. People who suffer from true IgE-mediated allergies can have up to 10 times the normal level of IgE in their blood (as do sufferers of hyper-IgE syndrome).
The IgE molecules (MW 200,000) bind to the surface of the mast cells and basophilic granulocytes. Subsequently the binding of allergen to cell-bound IgE causes these cells to release histamines and other vasoattive substances. The release of histamines in the body results initiates what is commonly known as an allergic reaction.
IgE levels show a slow increase during childhood, reaching adult levels in the second decade of life. In general, the total IgE levels increase with the allergies a person has and the number of times of exposure to the relevant allergens. Significant elevations may be seen in the sensitised individuals, but also in cases of myeloma, pulmonary aspergillosi, and during the active stages of parasitic infections.

The measurement of immunoglobulin E (IgE) in serum is widely used in the diagnosis of allergic reactions and parasitic infections. Before making any therapeutic determination it is important, however, to know whether the allergic reaction is IgE mediated or non- IgE mediated. Measurement of total IgE in serum sample, along with other supporting diagnostic information, can help to make that determination.

IgE ELISA:

Immunoenzymatic colorimetric method (ELISA) for quantitative determination of IgE in serum.

Principle of the Assay:

The essential reagents required for an immunoenzymometric assay include high affinity and specificity antibodies (enzyme and immobilized, with different and distinct epitope recognition, in excess, and native antigen. In this procedure, the immobilization takes place during the assay at the surface of a microplate well through the interaction of streptavidin coated on the well and exogenously added biotinylated monoclonal anti-IgE antibody. Upon mixing monoclonal biotinylated antibody, and a serum containing the native antigen, reaction results between the native antigen and the antibody, forming an Antibody-Antigen complex. The interaction is illustrated by the following equation: 

 
BtnAb(m) = Byotinilated Monoclonal Antibody (Excess Quantity)
AgIgE = Native Antigen (Variable Quantity)
E-Ab = enzyme labeled Antibody (Excess Quantity)
Ag(IgE)-BtnAb(m) = Antigen-Antibodies Complex (Variable Quantity)  
Ka = Rate Constant of Association
K-a = Rate Constant of Dissociation

Simultaneously, the complex is deposited to the well through the high affinity reaction of streptavidin and biotinylated antibody. This interaction is illustrated below:

Streptavidin CW = Streptavidin immobolized on well.
Immobilized Complex (IC) = Ag-Ab bound to the well.

After a suitable incubation period, the antibody-antigen bound fraction is separated from unbound antigen by decantation or aspiration. Another antibody (directed at a different epitope) labelled with an enzyme is added. Another interaction occurs to form an Enzyme labelled Antibody-Antigen-Biotinylated-Antibody complex on the surface of the wells. Excess enzyme is washed off via a wash step. A suitable substrate is added to produce colour measurable with the use of a microplate spectrophotometer. The enzyme activity on the well is directly proportional to the native free antigen concentration. By utilizing several different serum references of known antigen concentration, a dose response curve can be generated from which the antigen concentration of an unknown can be ascertained.

E(Ab-IgE) = Enzyme labelled Antibody (excess quanity)
E(Ab-IgE)-IC = Antigen-Antibodies complex
kb = Rate Constant of Association
k-b = Rate constant of dissoziation

Specific performance characteristics:

Correlation with another available IgE assay performed on 202 samples is r = 0.998

Order information: