The aim of the study is to analyze the mechanism of action of infliximab at the endomicroscopic level and to analyze mucosal healing - i.e. structural and functional changes in the mucosa in IBD patients - and associated processes such as permeability and bacterial invasion of the mucosa. In this study the role of the above mentioned parameters and further the establishment of endomicroscopic scores will serve to define new prognostic markers in view of long term remission upon infliximab treatment.