1. From the Pediatric Rheumatology, University Hospital Gasthuisberg, Leuven, Belgium; Laboratory of Experimental Transplantation, University of Leuven, Belgium; Department of Histopathology, University Hospital Gasthuisberg, Leuven, Belgium; Pediatric Transplantation, University Hospital Gasthuisberg, Leuven, Belgium; and Laboratory of Immunobiology, Rega-Institute for Medical Research, University of Leuven, Belgium.