Enzyme Immunoassay for the Quantitative Determination of Total IgE Concentration in Human Serum
Introduction
Immunoglobulin E (IgE) was identified as the fifth class of immunoglobulins in 1960 by Ishizaka and later introduced by Johansson and Bennich. IgE has a molecular weight of approximately 190 kDa and consists of two light chains (kappa or lambda) and two heavy chains of the epsilon isotype. IgE represents less than 0.001% of total serum immunoglobulins and is primarily secreted by peripheral blood B lymphocytes and plasma cells located in the spleen, gastrointestinal system, respiratory tract, and lymphoid organs (Hamilton & Adkinson, 2002).
Certain white blood cells, including basophils and mast cells, have membrane receptors specific to IgE. Serum IgE is undetectable at birth but increases with age. Elevated total IgE levels are commonly associated with atopic allergic diseases, such as atopic asthma, atopic dermatitis, and hay fever (Halonen et al., 1982). IgE also plays a crucial role in mediating hypersensitivity reactions and contributes to immune responses against parasitic infections, such as hookworm and clinical conditions like aspergillosis (Pauwels et al., 1978). Conversely, decreased IgE levels may be observed in conditions such as hypogammaglobulinemia, autoimmune diseases, ulcerative colitis, hepatitis, cancer, and malaria (Seagroatt et al., 1981).
Cord blood IgE levels have been explored for their prognostic value in predicting the risk of future allergic conditions in children (Haus et al., 1988). The concentration of IgE in an individual is dependent on the extent of allergic sensitization and the number of allergens to which they are exposed. Non-allergic individuals exhibit a broad range of IgE concentrations, which increase steadily during childhood, peak between ages 15–20, and decline after age 60 (Breg et al., 1969).
Clinical Significance
The measurement of total IgE is crucial in diagnosing and monitoring allergic diseases, immunodeficiency disorders, and parasitic infections. Elevated IgE levels are indicative of an increased likelihood of IgE-mediated hypersensitivity reactions, which are central to allergic conditions (Hamilton & Adkinson, 2002). This ELISA test provides a reliable and efficient method for assessing total serum IgE, aiding clinicians in diagnosing allergies, evaluating immune responses, and guiding patient management strategies.
Test Principle
The Total IgE Quantitative Test Kit is based on a solid-phase enzyme-linked immunosorbent assay (ELISA). This system utilizes a monoclonal anti-IgE antibody for solid-phase immobilization on microtiter wells and a mouse monoclonal anti-IgE antibody conjugated with horseradish peroxidase (HRP) in the antibody-enzyme conjugate solution.
The test sample is allowed to react with the immobilized antibodies. After incubation and washing, the enzyme conjugate is added, forming a sandwich complex between the solid-phase and conjugated antibodies. A chromogen-substrate solution is added, leading to a colorimetric reaction. The reaction is stopped with an acidic stop solution, and absorbance is measured spectrophotometrically at 450 nm. The intensity of the color is directly proportional to the IgE concentration in the sample.
References
- Breg, T., et al. (1969). Immunoglobulin levels during childhood, with special regard to IgE. Acta Paediatrica Scandinavica, 58, 513.
- Halonen, M., et al. (1982). An epidemiologic study of the inter-relationships of total serum immunoglobulin E, allergy skin-test reactivity, and eosinophilia. Journal of Allergy and Clinical Immunology, 69(3), 221-228.
- Hamilton, R. G., & Adkinson, N. F. (2002). Measurement of total serum immunoglobulin E and allergen-specific immunoglobulin E antibody. In N. R. Rose et al. (Eds.), Manual of Clinical Laboratory Immunology (4th ed., pp. 689-701). American Society for Microbiology.
- Haus, M., et al. (1988). The influence of ethnicity, atopic family history, and maternal ascariasis on cord blood serum IgE concentrations. Journal of Allergy and Clinical Immunology, 82, 179.
- Pauwels, R., et al. (1978). Total serum IgE levels in normal individuals and in patients with chronic non-specific lung diseases. Allergy, 33, 254-260.
- Seagroatt, V., et al. (1981). The second international reference preparation of human serum immunoglobulin E and the first British standard for human serum immunoglobulin E. Journal of Biological Standardization, 9, 431.