1. Division of Cytokine Biology, Center for Biologics Evaluation and Research, Bethesda, MD 20892, USA.
2. Biogen Incorporated, Cambridge, MA 02142, USA.
3. Public Health Research Institute, New York, NY 10016, USA.
4. Department of Microbiology and Cancer Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA.