1. Penn State University College of Medicine, Department of Biochemistry and Molecular Biology, H171, Milton S. Hershey Medical Center, P.O. Box 850, 500 University Drive, Hershey, Pennsylvania 17033
2. Department of Immunology, Howard Hughes Medical Institute, University of Washington School of Medicine, Seattle, Washington 98195
3. Department of Biomedical Research, Alfred I. duPont Hospital for Children, 1600 Rockland Road, Wilmington, Delaware 19803
4. The John Curtin School of Medical Research, The Australian National University, P.O. Box 334, Canberra, Australian Capital Territory 2601, Australia