1. Department of Small Animal Clinical Sciences (Bergman, Inzana, Monroe, Shell), Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg, Virginia 24061; the
2. Burnham Institute (Liu, Engvall), La Jolla, California 92037; and the
3. Department of Pathology (Shelton), University of California–San Diego, La Jolla, California 92093
4. From the