[1] Harvard Univ, Massachusetts Gen Hosp, Sch Med, Gastrointestinal Unit,Dept Med, Boston, MA 02114 USA
[2] Harvard Univ, Massachusetts Gen Hosp, Sch Med, Dept Pathol, Boston, MA 02114 USA
[3] Harvard Univ, Massachusetts Gen Hosp, Sch Med, Ctr Study Inflammatory Bowel Dis, Boston, MA 02114 USA
[4] Univ Chicago, Div Gastroenterol, Dept Med, Chicago, IL 60637 USA