IgE stands for immunoglobulin E, and is one of five types of immunoglobulins involved in immune sensitivity and response in humans. However, IgE is found exclusively in mammals. Immunoglobulins, more commonly known as antibodies, also belong to a family of proteins referred to as gamma globulins. They are produced by specific white blood cells called B-lymphocytes. Collectively, IgEs, which reside in the blood, are important weapons used by the immune system to detect and respond to the invasion of foreign substances, namely bacteria and viruses.
As might be expected, IgE is also involved in allergy hypersensitivity and allergic reactions. In fact, IgE is the primary mediator that stimulates the release of inflammatory agents in mast cells, such as histamine and leukotrienes. In addition, it is responsible for triggering the most severe allergic reactions, even though it is usually the immunoglobin found least in circulation in the blood. In addition, there is sufficient evidence to suggest that IgE is involved in immune responses to parasitic invasions and the increased white blood cell count associated with the onset of cancer.
The role of IgE is to target and bind to a particular protein found on the surface of certain cells, such as mast cells, macrophages, and natural killer (NK) cells. These proteins are referred to as Fc receptors and are further classified depending on the specific antibody that they bond with. Receptors that differentiate IgE specifically are called Fc-epsilon receptors (FcεR). The result of their bonding together is the release of inflammatory mediators (i.e., histamine) that produce inflammation in smooth muscles and increase mucous secretions.
While IgE is involved in skin allergies resulting from direct contact with an allergen, it is also involved in atopic reactions, indicating hypersensitivity without direct contact. In fact, excessively high serum levels of IgE antibodies usually accompany inflammatory conditions like eczema. However, in terms of asthma, which is also an inflammatory disease, the predictable allergic response may occur even though blood concentrations of IgE antibodies are relatively low. This is because once an allergic reaction has been initiated, the protein receptors become “primed,” or programmed to recognize the same allergen when introduced and respond in the same way as before.
The typical treatment of IgE-induced allergy is treatment with medications such as antihistamines. While the name implies that the production of histamine is hindered, what actually occurs is histamine being blocked from release at receptor cites. However, new drugs are being developed with the aim to prohibit IgE from binding to these receptor sites in the first place.