1. The Jackson Laboratory, Bar Harbor, Maine 04609-1500
2. Departments of Surgery, Cell and Developmental Biology, Vanderbilt School of Medicine, Nashville, Tennessee 37212
3. Department of Veterinary Biosciences, The Ohio State University, Columbus, Ohio 43210
4. NIAID, Bethesda, Maryland 20892, and
5. Transgenic Inc., Kumamoto 860-0802, Japan