1. From the Laboratory Service, Veterans Affairs Health Care System, Palo Alto, California, USA
2. Department of Pathology, Stanford University School of Medicine, Stanford, California, USA
3. Department of Comparative Medicine, Stanford University School of Medicine, Stanford, California, USA
4. Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, California, USA
5. Department of Medicine, Stanford University School of Medicine, Stanford, California, USA