Immunoglobulin E, Total

The concentration of IgE in serum of normal individuals typically represents <0.001% of the total immunoglobulins present.^1,2 Immunoglobulins of the IgE class play an important role in mediating the atopic reactions that occur when sensitive individuals are exposed to allergens. IgE has a structure that is similar to other immunoglobulins in that it consists of four chains: two light chains and two heavy chains.¹ The heavy chains for each IgE molecule contain a variable region that accounts for antigen specificity. Since IgE myeloma is extremely rare, the clinical utility of measuring IgE levels generally involves its role as the mediator of the allergic response. The majority of IgE molecules in serum are bound to the surface of mast cells and basophilic granulocytes. The interaction of allergens with the cell-bound allergen-specific IgE causes these cells to release histamines and other vasoactive substances, thereby initiating the allergic reaction. Approximately 50% of individuals with allergic rhinitis or asthma will have elevated levels of IgE;¹ however, a large number of individuals with allergy and elevated levels of IgE to specific allergens will have normal levels of total IgE. Studies have indicated that total IgE levels are often elevated in patients with atopic dermatitis and the concentration of IgE tends to correlate with severity of eczema.¹ Total IgE levels can also be elevated in patients with parasitic infections, allergic bronchopulmonary aspergillosis, or immunodeficiency.^1,2