 Infliximab, a monoclonal IgG1 antibody to the pro-inflammatory cytokine tumor necrosis factor-alpha TNF-α, was the first efficacious biological therapy for IBD. Infliximab dramatically improved the quality of life in IBD patients. Besides inducing and maintaining remission in refractory IBD patients, infliximab has achieved new treatment goals such as intestinal mucosal healing and a reduction in hospitalizations and surgeries on the long-term. However, up to 30 of IBD patients do not respond to this costly therapy and potentially harmful therapy, and in an extra 20-30 response is incomplete. The mechanism of resistance to infliximab is unknown and predictors of response to infliximab are currently lacking. 