IGHE

Immunoglobulin E (IgE) is a type of antibody (or immunoglobulin (Ig) "isotype") that has been found in mammals. IgE is synthesized by plasma cells. Its main function is immunity to parasites such as helminths like Schistosoma, Trichinella, and Fasciola. However, IgE also plays a pivotal role in type I hypersensitivity, which manifests in various allergic diseases, such as allergic asthma, allergic rhinitis, and food allergies, as well as some forms of chronic urticaria and atopic dermatitis. IgE also has an essential role in allergic reactions to drugs, and it is a target of allergy immunotherapy (allergen immunotherapy).

Structure and Function

IgE's structure is similar to that of other antibody isotypes, consisting of two heavy chains (ε chain) and two light chains, with the heavy chains containing four immunoglobulin domains (unlike other antibodies which typically have three). This structure allows IgE to bind to antigens with high specificity. Upon binding to an antigen, IgE can trigger an immune response, particularly involving the release of histamine from mast cells and basophils, which are involved in the inflammatory response.

Role in Allergy and Asthma

In allergic reactions, an allergen-specific IgE is overproduced, leading to the sensitization of mast cells and basophils. Upon re-exposure to the allergen, these cells are prompted to release various inflammatory mediators, such as histamine, leading to the symptoms associated with allergies. In asthma, IgE levels are often elevated, and targeting IgE has become a therapeutic strategy, exemplified by the development of monoclonal antibodies such as Omalizumab, which binds to IgE and prevents it from interacting with its receptor on mast cells and basophils.

Regulation of IgE Production

The production of IgE is tightly regulated by the immune system, involving interactions between B cells, T cells, and other immune cells. Interleukin-4 (IL-4) and Interleukin-13 (IL-13) are crucial in the switching of B cells to IgE production. Genetic factors also play a significant role in the regulation of IgE levels in the body, influencing susceptibility to allergic diseases.

Clinical Significance

Measurement of total serum IgE levels is a common diagnostic tool for allergic diseases. Specific IgE testing, targeting IgE antibodies specific to particular allergens, can help in identifying specific allergic sensitivities. Elevated IgE levels can be indicative of allergic diseases, parasitic infections, and some rare immune disorders.

Therapeutic Approaches

The understanding of IgE's role in allergic diseases has led to the development of targeted therapies aimed at reducing IgE levels or blocking its activity. Besides Omalizumab, other strategies include allergen immunotherapy, which aims to desensitize the immune system to specific allergens, potentially reducing the severity of allergic reactions.