Transglutaminase 2 and Transglutaminase 2 Autoantibodies in Celiac Disease: a Review

Celiac disease is a common inflammatory disorder with a prevalence of 1-2 % in which a distinct dietary wheat, rye, and barley component, gluten, induces small-bowel mucosal villous atrophy, crypt hyperplasia, and inflammation. The small-bowel mucosal damage can be reversed by a strict lifelong gluten-free diet, which is currently the only effective treatment for the condition. A key player in the pathogenetic process leading to the enteropathy is played by a protein called transglutaminase 2 (TG2), which is able to enzymatically modify gluten-derived gliadin peptides. The TG2-catalyzed deamidation of the gliadin peptides results in their increased binding affinity to the disease-predisposing human leukocyte antigen (HLA) DQ2 and DQ8 molecules, thus enabling a strong immune response to be launched. Blocking the enzymatic activity of TG2 has thus been suggested as a suitable novel pharmacological approach to treat celiac disease. By virtue of its transamidation capacity, TG2 is also able to cross-link gliadin peptides to itself, this resulting in the generation of TG2-gliadin peptide complexes whose presence might provide an explanation for the generation of the TG2 autoantibodies characteristic of celiac disease. Due to their excellent specificity for the disorder, the TG2-targeted autoantibodies are widely used in the diagnostics as a first-line test to select patients for gastrointestinal endoscopy. More recently, it has come to be appreciated that these autoantibodies and also the TG2-specific B cells might play an active role in the disease pathogenesis. In this review, we assess the role of TG2, TG2-specific B cells, and autoantibodies in celiac disease.