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Immunoglobulin E (IgE) is a type of antibody (or immunoglobulin (Ig) "isoform") that has been found only in mammals. IgE is synthesised by plasma cells. Monomers of IgE consist of two heavy chains (ε chain) and two light chains, with the ε chain containing four Ig-like constant domains (Cε1–Cε4). [1]
The difference between a normal infectious immune response and a type 1 hypersensitivity response is that in type 1 hypersensitivity, the antibody is IgE instead of IgA, IgG, or IgM. During sensitization, the IgE antibodies bind to FcεRI receptors on the surface of tissue mast cells and blood basophils. [3]
These cytokines mediate the activation of type 2 T helper cells (T h 2 cells), type 2 innate lymphoid cells (ILC2 cells), and dendritic cells. T h 2 cells and ILC2 cells secrete IL-4, IL-5 and IL-13. [1] [3] IL-4 further drives CD4+ T cell differentiation towards the T h 2 subtype and induces isotype switching to IgE in B cells.
Immediate reactions are caused by an allergen-specific immunoglobulin E (IgE) antibody that floats around in the blood stream. Another useful tool in diagnosing and managing food allergies is blood testing, called allergen-specific IgE testing. This test measures the level of antibody produced in the blood in response to a food allergen. [10]
Each heavy chain has two regions: a constant region (which is the same for all immunoglobulins of the same class but differs between classes).. Heavy chains γ, α and δ have a constant region composed of three tandem (in a line next to each other) immunoglobulin domains but also have a hinge region for added flexibility.
Antibody (or immunoglobulin) structure is made up of two heavy-chains and two light-chains.These chains are held together by disulfide bonds.The arrangement or processes that put together different parts of this antibody molecule play important role in antibody diversity and production of different subclasses or classes of antibodies.
An IgE level greater than 2,000 IU/mL is often considered diagnostic. [17] However, patients younger than 6 months of age may have very low to non-detectable IgE levels. Eosinophilia is also a common finding with greater than 90% of patients having eosinophil elevations greater than two standard deviations above the normal mean. [ 18 ]
Red blood cells carrying CR1-receptors on their surface may bind C3b-coated immune complexes and transport them to phagocytes, mostly in liver and spleen, and return to the general circulation. The ratio of antigen to antibody determines size and shape of immune complex. [3] This, in turn, determines the effect of the immune complex.