He is a professor at the David Geffen School of Medicine at UCLA, and Chair of the Department of Pathology and Laboratory Medicine, a diverse clinical and academic enterprise including over 100 faculty, 100 trainees, and 1200 staff. His recent national service includes the Board of Editors of Gastroenterology; membership on several NIH advisory panels; Director of the UCLA Clinical and Translational Science Institute, Chair of the National Scientific Advisory Committee of the Crohn’s and Colitis Foundation; Chair of the Scientific Board, Milieu Interieur, Institute Pasteur; President of the Clinical Immunology Society; and, co-founder and President of the Federation of Clinical Immunology Societies.