IgE or type E immunoglobulins are part of the family of immunoglobulins that include 5 classes: IgG, IgA, IgM, IgD and IgE. They exist in minute quantities in a normal subject, and they are cytophilic (i.e., in particular they bind to the mastcell and the basophil) and are homocytotropic. Generally, they are found mainly in perivascular tissue where are located the mast cell to which they bind through specific receptors.The cross-linking of IgE and an antigen-specific IgE on the membrane of a mast cell produces the mast cell degranulation; the expelled granules contain many mediators including histamine. Thus, IgE play a major role in immediate-onset allergy and in the symptoms of the atopic patient. Serum high total IgE levels are also associated with atopic dermatitis but measurement of serum levels is not useful in an isolated subject.
The production of IgE results from stimuli and controls
different from that of other immunoglobulins.
Exposure to small quantities of allergens promotes the IgE
production, while exposure to larger quantities generally promotes
the IgG production.