1. F. Papavasiliou, R. Casellas, X.-F. Qin, Laboratory of Molecular Immunology, Rockefeller University, New York, NY 10021, USA.
2. H. Suh, E. Besmer, M. C. Nussenzweig, Laboratory of Molecular Immunology and Howard Hughes Medical Institute, Rockefeller University, New York, NY 10021, USA.
3. R. Pelanda, Max Plank Institute for Immunobiology, Freiburg, Germany 79108.
4. D. Nemazee, Division of Basic Sciences, Department of Pediatrics, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206, USA.
5. K. Rajewsky, Institute for Genetics, University of Cologne, Weyertal, Germany 50931.