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IgE is typically the least abundant isotype: blood serum IgE levels in a non-atopic individual are less than 0.0001% of the total Ig concentration, [10] compared to 75% for the IgGs at 10 mg/ml. Despite this, it is capable of triggering anaphylaxis, one of the most rapid and severe immunological reactions. [11]
Histamine, a biogenic amine found in various food products, is frequently implicated as a potential instigator of a range of health issues. [1] These issues are often collectively referred to under the umbrella term "histamine intolerance", [1] formulated drawing parallels to "lactose intolerance", a condition resulting from lactase enzyme deficiency.
Reference ranges (reference intervals) for blood tests are sets of values used by a health professional to interpret a set of medical test results from blood samples. Reference ranges for blood tests are studied within the field of clinical chemistry (also known as "clinical biochemistry", "chemical pathology" or "pure blood chemistry"), the ...
A value of greater than 1.5 units relative to a control serum is considered a positive ELISA test for the anti-histone antibodies. Patients with drug-induced lupus erythematosus typically have positive tests for anti-histone antibodies but do not have indications for anti-dsDNA antibodies. Patients with idiopathic systemic lupus erythematosus ...
Commercial laboratories provide a 24-hour urine sample test for 1,4-methyl-imidazolacetic acid, the metabolite of histamine. This test is a valuable tool in assessing the metabolism of histamine in the body, as direct measurement of histamine in the serum has low diagnostic value due to the specificities of histamine metabolism. [48] [49] [50]
In type I hypersensitivity, B cells are stimulated (by CD4 + T h 2 cells) to produce IgE antibodies specific to an antigen. 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.
Type III hypersensitivity, in the Gell and Coombs classification of allergic reactions, occurs when there is accumulation of immune complexes (antigen-antibody complexes) that have not been adequately cleared by innate immune cells, giving rise to an inflammatory response and attraction of leukocytes.
During pregnancy, DAO helps maintaining fetal growth and development by regulating histamine levels. [11] DAO levels in the blood circulation increase vastly in pregnant women suggesting a protective mechanism against adverse histamine. [12] Histamine is a potent vasodilator and can cause uterine contractions, which can lead to premature labor.