1. Central Laboratory of the Netherlands Red Cross Blood Transfusion Service and Laboratory for Experimental and Clinical Immunology, University of Amsterdam
2. Department of Internal Medicine, Onze Lieve Vrouwe Gattuis
3. Department of Internal Medicine, Academical Medical Centre
4. Department of Infectious Diseases, Municipal Health Service, Amsterdam
5. Department of Internal Medicine, Bronovo Hospital, The Hague, The Netherlands