1. Hospital Clínico Universitario and Unidad Mixta de Investigación, Zaragoza, Spain
2. Department of Gastroenterology and Laboratory of Gastrointestinal Immunogenetics, Vrije Universiteit Medical Center, Amsterdam, the Netherlands
3. Department of Gastroenterology, Hospital Clínico Universitario and Unidad Mixta de Investigación, Zaragoza, Spain