 This study will examine the safety and effectiveness of extracorporeal photopheresis ECP in controlling Crohns disease symptoms as patients taper their corticosteroid dose. Crohns disease is a chronic inflammatory bowel disease. Patients commonly have chronic diarrhea with abdominal pain, loss of appetite and weight loss. Acute disease flares are treated with large doses of corticosteroids, but long-term use of these drugs can have harmful side effects. ECP described below, is approved to treat skin symptoms associated with a type of cancer called cutaneous T-cell lymphoma and has been used experimentally in conditions involving abnormal inflammation. 