Endothelial cell chimerism after renal transplantation and vascular rejection

Background The blood vessels of a transplanted organ are the interface betw een donor and recipient. The endothelium in the blood vessels is thought to be the major target for graft rejection. Endothelial cells of a transplant ed organ are believed to remain of donor origin after transplantation. We a imed to verify this concept. Methods We studied biopsy samples from 12 renal transplants for the presenc e of endothelial cells of recipient origin. We used three different techniq ues: immunohistochemistry for MHC class-I antigens, immunohistochemistry fo r ABO-blood-group antigens, and in-situ hybridisation for X and Y chromosom es. After we had conformed that these techniques did identify endothelial c ells of recipient origin, tests were done in a second group of 26 patients to find out whether endothelial chimerism correlated with graft rejection. Findings We found a strong correlation between the percentage of recipient endothelial cells in the peritubular capillaries and the type of graft reje ction (r=0.71, p<0.0001). These cells were found mainly in grafts of patien ts who had had rejection, especially among patients with vascular rejection . In grafts of patients without rejection only sporadically recipient endot helial cells were delectable. Interpretation Our data show that endothelial cells of the recipient can re place those of the donor. This replacement is associated with graft rejecti on, We postulate that endothelium that is damaged by vascular rejection is repaired by endothelial cells of the recipient.