1. Department of Dental Basic Sciences, Academic Centre for Dentistry Amsterdam -ACTA-, Van der Boechorststraat 7, 1081 BT Amsterdam, the Netherlands;
2. Department of Oral & Maxillofacial Surgery/Oral Pathology, University Medical Centre Vrije Universiteit -VUMC-, Amsterdam, The Netherlands; and
3. Department of Immunology and Microbiology, Institute for Medical Biology, University of Southern Denmark, 5000 Odense C, Denmark;