A CELL SURFACE TISSUE TRANSGLUTAMINASE IS INVOLVED IN RECOGNITION OF GLIADIN PEPTIDES BY K 562 CELLS

Abstract

Aim: Several studies have been demonstated that the agglutination activity of human chronic myelogenous leukemia K562 cells by prolamines peptictryptic digest (PT) is higly correlated with the toxicity of these prolamines in coeliac disease. The mechanism of the agglutination activity is unknown, but the presence of a binding site on cell surface of K562 cells has been supposed. In the latest years, a cell surface tissue transglutaminase has been identified in CD8 + T cell, in monocytes and in K562 cells. Tissue transglutaminase is known to play a pivotal role in pathogenesis of coeliac disease, binding the gliadin peptides in the small bowel mucosa of these patients. We hypothesize that the cell surface transglutaminase could have a role in the agglutination activity of K562 cells. Methods: K562 cells were grown in RPMI medium. For the agglutination test, cells were harvested, washed and resuspended in PBS at the final concentration of 108cells/ml. The agglutination test were carried out as follow: in each well of a 96 well plate 25 μl of PBS and 25 μl of cells were added. Then, mAb anti tTG CUB 7402 (Neomarker, USA) 1 μl of a solution at the concentration of 2 μg/ml and 25 μl of a 0,5 mg/ml PT solution were added. Finally, an incubation for 30 min occoured before evaluating the agglutination by optical microscope. Controls were performed with PT only and with mAB anti rabbit IgG. Results: The incubation of K562 cells with PT digest resulted in a massive agglutinationof the cells. No agglutination occoured when the mAb anti tTG was added prior to the PT digest. Summary: The ability of the mAb anti tTG of preventing the agglutination of K562 by gliadin peptides indicates that a cell surface tissue transglutaminase acts as binding site for the gliadin peptides. Conclusion: The results of these study suggest that tissue transglutaminase could play a role in recognition of gliadin peptides by the cells in coeliac disease and it could be involved in starting other responses than the activation of the adaptive immune system in the mucosa of the coeliac disease patients.