1. Postdoctoral Fellow, Department of Physiology, Stanford University School of Medicine.
2. Visiting Scholar, Linus Pauling Institute.
3. Research Microbiologist, Palo Alto Veterans Administration Hospital.
4. Research Immunophysiologist, Department of Physiology, Stanford University School of Medicine.
5. Barnett Professor of Medicine, Stanford University School of Medicine and Staff Gastroenterologist, Palo Alto Veterans Administration Hospital.
6. Professor of Physiology, Stanford University School of Medicine.