Supplementary Histamine ELISA

In humans, histamine (ß-imidazole ethylamine) is the most important mediator and is mostly found in the initial phase of an anaphylactic reaction ("immediate type" allergy). Histamine is produced by the enzymatic decarboxylation of histidine. In the organism, histamine is present in nearly all tissues, and it is mainly stored in the metachromatic granules of mast cells and the basophilic leukocytes. It is present in an inactive bound form and is released only as required. Histamine acts predominantly on smooth muscle and blood vessels. In humans, it is responsible for the broncho-constriction occurring during the acute phase. In the vessels, its constrictive effect is limited to the venula, whereas arterioles are dilated. Furthermore, histamine causes a contraction of the cells of the vascular endothelium and increases the vascular permeability, thereby allowing higher-molecular substances to escape into the tissue. Like several other mediators, histamine does not exclusively mediate various clinical symptoms of anaphylaxis but also induces a series of effects which are directed towards a termination of the anaphylactic reaction. Histamine may inhibit the release of lysosomal enzymes from polymorphonuclear leukocytes, the degranulation of mast cells and basophiles and the production of complement components through mononuclear phagocytes. Furthermore, histamine can activate suppressor T cells and, thus, may inhibit the production of IgE. The biological action of histamine in tissue is guaranteed by three different surface receptors, i.e. H1, H2 and H3 receptors. Heparinized whole blood samples are incubated with different concentrations of the suspected allergen. Release of histamine will occur upon stimulation of basophilic granulocytes depending on their sensibility to the allergen. The released histamine in the supernatant is subsequently determined using a specific plasma immunoassay, the Histamine ELISA purchased in connection with this kit. This histamine value is related to the 100% control (= Total Histamine) and the blank value (= Spontaneous Release).