1. Regenerative Immunology and Aging, Berlin-Brandenburg Center for Regenerative Therapies, Charité University Medicine, Berlin, Germany;
2. Institute for Theoretical Biology, Humboldt University of Berlin, Berlin, Germany;
3. Institute for Medical Microbiology, Technical University Munich, Munich, Germany;
4. Allergie-Centrum-Charité, Charité University Medicine, Berlin, Germany; and
5. Department of Microbiology, University of Pennsylvania, Philadelphia, PA