Impairment of the tight junction (TJ) is linked to enhanced luminal antigen uptake supporting inflammatory processes in IBD. We hypothesize that especially the tricellular tight junction (tTJ) is crucially involved in this and in immune cell activation. Thus, we will analyze effects and interactions between the (t)TJ and the immune cells beyond during development of intestinal inflammation. Elucidation of regulatory pathways beyond will identify possible targets of intervention, which then will be used for strategies stabilizing the (t)TJ barrier preventing antigen entry and perpetuation of inflammation in order to protect against development of IBD.