1. Department of Microbiology,1
2. Molecular Biology Program,2
3. University of Colorado Cancer Center,3 and
4. Biomedical Sciences Program,4 University of Colorado Health Sciences Center, Denver, Colorado;
5. Division of Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington5;
6. Biology Department, Brookhaven National Laboratory, Upton, New York6; and
7. Department of Haematology, University Hospital Utrecht,7 and
8. Laboratory for Physiological Chemistry, Utrecht University,8 Utrecht, The Netherlands