Endomysium antibodies (abbreviated: EmA) are autoantibodies directed against endogenous proteins of the endomysium of muscle cells. These proteins are the tissue transglutaminase . Tissue transglutaminase is therefore the relevant antigen of the endomysium.
The serological diagnosis of the antibodies must always be carried out with sufficient gluten intake. A selective IgA deficiency (determination of total IgA) must be excluded beforehand (prevalence of congenital IgA deficiency: 2 %). In the presence of IgA deficiency, endomysium or transglutaminase IgA antibodies are not formed.
Together with the determination of auto-Ak (IgA) against transglutaminase antibodies (tTG) or endomysium antibodies (EMA ), auto-Ak (IgA) against gliadin have the highest diagnostic significancein celiac disease.
Endomysium IgA antibodies, even in isolation, have a high sensitivity and specificity (probability that actually healthy persons who do not suffer from the disease in question are also identified as healthy in the test; 95-100 % )for the diagnosis of celiac disease.
Under a gluten-free diet, the endomysium IgA antibody titers regularly normalize.
These autantibodies can be visualized with many tissues, e.g. primate esophagus. However, frozen sections of primate liver are most suitable. Here, positive sera show a reaction of the filamentous linings of the intralobular sinusoids.