Inclusion Criteria:  ECP treatment decision based on transplant team habits (care management) Age ≥ 18 years Affiliation to a French social security scheme Kidney transplant at least 6 months prior to inclusion  cABMR proven by a renal graft biopsy less than 3 months and meeting the following histological criteria:  allograft glomerulopathy (cg>0, and maximum score cg2) or intimal fibrosis C4d positive or ptc+g greater than or equal to 2 Presence of Donor Specific Antibody (DSA) Interstitial Fibrosis and Tubular Atrophy (IFTA) less than or equal to 2 Glomerular filtration rate > 30 mL/min/1.73 m2 Signed informed consent to participate in the study  Exclusion Criteria:  Active infection or infection with hepatitis B, C or HIV virus Pregnant, breastfeeding or parturient woman Person deprived of liberty by judicial or administrative decision Person receiving psychiatric care under duress Person subject to legal protection Person out of state to express consent