1. Department of Gastroenterology and Hepatology, University Hospital Essen, University of Duisburg-Essen, Germany.
2. Department of General, Visceral, and Transplantation Surgery, University Hospital Essen, University of Duisburg-Essen, Germany.
3. Institute of Immunology, University Hospital Essen, University of Duisburg-Essen, Germany.
4. Department of Dermatology, University of Bonn, Germany.