- Kidney transplant patient with iterative biopsies with at least: post-surgery biopsy D0 (or early post-transplant biopsy D7 and at least one biopsy protocol. - Age> 18 years Case group: - Kidney transplant patient, followed up by "organ transplant unity" of CHU Toulouse, with antecedent of CMR progressing to CTG between 2006 and 2013. Control group: - Kidney transplant patient, followed up by "organ transplant unity" of CHU Toulouse, with antecedent of CMR without progressing to CTG between 2006 and 2013