1. Paediatric Gastroenterology, Hepatology and Liver Transplantation, Hanover Medical School, 30625 Hanover, Germany
2. Institute of Epidemiology and Social Medicine, University of Muenster, 48149 Muenster, Germany
3. Department of Paediatrics and Adolescent Medicine, University Medical Centre Goettingen, Georg August University, 37075 Goettingen, Germany
4. Paediatric Surgery, Hannover Medical School, 30625 Hanover, Germany
5. Institute of Immunology and Immunotherapy, University of Birmingham, Birmingham B15 2TT, UK