The purpose of this study is to determine whether infliximab can favourably and safely be discontinued in patients with Crohn's disease in sustained complete clinical, biochemical, and endoscopic remission on infliximab.||Further to examine the clinical utility of measuring levels/activity of infliximab and activity of anti-infliximab Ab in patients in sustained complete remission, in order to investigate whether pharmacoimmunological data can predict the clinical outcome and rationalize therapeutic management of these patients with respect to continuation or discontinuation of infliximab therapy. Additional, to investigate the optimal time-point, out of three, to measure this activity.