1. Eukaryotic Genetics Group, Biotechnology Research Institute, National Research Council of Canada, Montreal, Quebec H4P 2R2, Canada; the
2. Institute of Clinical Microbiology, Immunology, and Hygiene, University of Erlangen, D-91054 Erlangen, Germany; and the Departments of
3. Anatomy and Cell Biology,
4. Biology, and
5. Experimental Medicine, McGill University, Montreal, Canada