1. D. J. Rawlings, H. Park, M. I. Wahl, R. M. Kato, A.-C. Fluckiger, Department of Microbiology and Molecular Genetics, University of California, Los Angeles, CA 90095-1662, USA.
2. A. M. Scharenberg, S. Lin, J.-P. Kinet, Laboratory of Allergy and Immunology, Beth Israel Hospital, and Harvard Medical School, 99 Brookline Avenue, Boston, MA 02215, USA.
3. O. N. Witte, Howard Hughes Medical Institute and Molecular Biology Institute and the Department of Microbiology and Molecular Genetics, University of California, Los Angeles, CA 90095-1662, USA.