Expression pattern of transglutaminase 2 in human small intestine

VERBECKE S; CALDERÓN JF; CHIRDO FG; BRUNSER O

Cordoba

Congreso; VII Latin American Congress of Immunology; 2005

Asociación Latinoamericana de Inmunología

Tissue transglutaminase (TG2) belongs to a family of Ca2+-transamidating enzymes. TG2 also has GTPase activity in second active site and participates in wound healing, signalling, differentiation and apoptosis. TG2 is involved in the pathogenesis of celiac disease, since gliadin peptides deamidated by TG2 and presented in HLA-DQ2/DQ8, MHC class II predisposing alleles, enhance T cell stimulation. The covalently linked complex TG2/gliadins may explain the induction of autoanti-TG2 antibodies in celiacs. The aim of this study was to locate TG2 in the intestinal mucosa using anti-TG2 monoclonal antibodies. Biopsies of duodenal mucosa from paediatric controls and celiac patients were fixed and included in LR Gold for immuno electronmicroscopy. Thin sections were incubated with epitope-mapped anti-TG2 monoclonal antibodies; and with gold-labelled secondary antibody. TG2 was detected in the outer membrane of microvilli (brush border), in the outer membrane of mitochondria and less frequently in the mitochondrial matrix, in the outer membrane of the endoplasmic reticulum and occasionally in the nucleus of enterocytes, as well as in the basolateral cell membrane but not in the intercellular space of the epithelium. The Golgi apparatus was not labelled. Labelling was more frequent subjacent to the basement lamella than in the basement lamella itself. No differences in location could be established between controls and celiac patients. In conclusion, TG2 is present in many structures of enterocyte. The ultrastructural locations observed are in agreement with some of the biological functions proposed for TG2. Differential localization of TG2 in celiac compared with normal mucosa was not observed.