Tissue transglutaminase antibodies

Anti-tTG IgA, IgG (atTg) are antibodies to tissue transglutaminase. Tissue transglutaminase is directly related to the pathogenesis of the disease and has been described as the endomysium's own chemical substrate. Tissue transglutaminase (transglutaminase II isoenzyme, TG2 - EC 2.3.2.13), is a transferase, the system name is protein-glutamine: amine-γ-glutamyltransferase. It is a Ca 2+ dependent enzyme catalyzing the deamination of glutamine to glutamate, it also leads to the intramolecular binding of glutamine to another primary amine, eg lysine, and leads to aggregation of glutamine peptides. The determination of antibodies to tissue transglutaminase (atTG) therefore also has a very high diagnostic efficiency, similar to antibodies against endomysium ( sensitivity 87-97% and specificity 88-98%).

The determination of atTG is performed by the classical ELISA method, which is a technique more available for routine diagnostics than immunofluorescence detection of anti-endomysium antibodies (EmA).

Unlike EmA, atTG antibodies can be determined in both IgA and IgG classes, which is important for patients with selective IgA deficiency. The method was described using guinea pig antigen, which is used in most older kits. Newer kits already use tissue transglutaminase isolated from human cells, human erythrocytes, or recombinant tTG isolated from E. coli as antigen. The reference values ​​differ for individual kits, usually the upper limit of the standard 10–15 IU / l is given for IgA antibodies, some kits also define the so-called gray-zone) in the range of 10-20 IU / l. Determination of atTG antibodies with human recombinant antigen shows lower false positivity than guinea pig antigen methods. Recent studies compare IgA and IgG antibodies and POCT methodologies for the determination of atTG antibodies.

The determination of atTG antibodies in the IgA class is recommended as a basic screening test for the diagnosis of celiac disease.

Source

 * with the permission of the author taken from KOCNA, Petr. GastroLab: MiniEncyclopedia of laboratory methods in gastroenterology  [online]. © 2002. Last revision 2011-01-08, [cit. 2011-03-04]. < http://www1.lf1.cuni.cz/~kocna/glab/glency1.htm >.