1. K. C. Wolthers, S. A. Otto, A.-M. de Roda Husman, N. Schaft, L. Meyaard, Department of Clinical Viro-Immunology, Central Laboratory of the Netherlands Red Cross Blood Transfusion Service and Laboratory for Experimental and Clinical Immunology of the University of Amsterdam, Amsterdam, Netherlands.
2. G. B. A. Wisman and A. G. J. van der Zee, Department of Gynaecology and Obstetrics, Academic Hospital Groningen, University of Groningen, Groningen, Netherlands.
3. F. de Wolf and J. Goudsmit, Department of Human Retrovirology, Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands.
4. R. A. Coutinho, Department of Public Health, Municipal Health Service, Amsterdam, Netherlands.
5. F. Miedema, Department of Clinical Viro-Immunology, Central Laboratory of the Netherlands Red Cross Blood Transfusion Service and Laboratory for Experimental and Clinical Immunology of the University of Amsterdam, Amsterdam, Netherlands, and Department of Human Retrovirology, Academic Medical Centre, University of Amsterdam, Amsterdam, Netherlands.