1. Sanquin Research, Department of Immunopathology and Laboratory for Experimental and Clinical Immunology, Academic Medical Centre, University of Amsterdam, 1066 CX, Amsterdam, The Netherlands, Department of Dermatology and Allergology, UMC Utrecht, 3584CX, Utrecht, The Netherlands, Department of Allergology, Paul Ehrlich Institut, D-63225, Langen, Germany, and Food Allergy Research and Resource Program, University of Nebraska, Lincoln, Nebraska 68583-0919