<qa>  What is the goal of extracorporeal photopheresis therapy?This protocol aims to measure the safety and effectiveness of extracorporeal photopheresis ECP therapy for maintaining remission of symptoms during withdrawal of corticosteroids from patients with steroid-dependent Crohns disease. Potential subjects will be asymptomatic or have a low level of symptoms that respond to an increase in their steroid dose; furthermore potential subjects will be dependent on steroids to control their symptoms and have a history of failing other immunosuppressive drugs to control their symptoms. 