1. From the Central Laboratory of the Netherlands Blood Transfusion Service (CLB), and Laboratory for Experimental and Clinical Immunology, Academic Medical Center, University of Amsterdam, Amsterdam, and Department of Biomolecular Sciences, Laboratory of Biochemistry, Wageningen University, Wageningen, The Netherlands; Hospital de la Santa Creu I Sant Pau, Barcelona, Spain; Departments of Chemical Pathology and Paediatrics, Prince of Wales Hospital, Shatin, NT, Hong Kong.