Frans Claas is director of the Eurotransplant Reference laboratory and professor ‘Immunogenetics of transplantation”. His main research topics are the differential immunogenicity of HLA mismatches in clinical transplantation and the immunology of pregnancy as a model for transplantation tolerance. He was the initiator of a special program within Eurotransplant to enhance transplantation of highly sensitized renal transplant patients on basis of acceptable HLA mismatches. He is an editor in chief of Transplant Immunology.