One-year protocol biopsies from ABO-incompatible renal allografts compared with a matched cohort of ABO-compatible allografts

INTRODUCTION Early acute antibody-mediated rejection (ABMR) occurs more frequently in ABO-incompatible (ABOi) than in ABO-compatible (ABOc) kidney transplantation. This could lead to increased inflammation/scarring in the ABOi grafts. Protocol biopsy data in ABOi kidney recipients are scarce. METHODS A single-center retrospective matched cohort study was conducted. Eighty adult living donor (LD) renal transplant recipients without HLA donor-specific antibodies (DSA) transplanted between 2009 and 2012 were included; 20 ABOi and 60 ABOc controls matched for donor age and transplantation year. Protocol biopsies at one yr were scored according to the Banff classification. Three sums of scores were constructed: tubulointerstitial inflammation (t + i = 0 vs. >0), microvascular inflammation (g + ptc = 0 vs. >0), scarring/hyalinosis (ci + ct + cv + ah ≤ 1 vs. >1. Scores and presence of subclinical rejection (SCR) at one yr were compared. RESULTS Protocol biopsy findings at one yr in the ABOi vs. ABOc matched control group were not statistically different: (t + i) > 0, 30% vs. 20%; (g + ptc) > 0, 5% vs. 8%; (ci + ct + cv + ah) > 1, 85% vs. 60%, respectively. No transplant glomerulopathy occurred. SCR rate at one yr was 30% vs. 18%, subclinical ABMR 5% vs. 7% (all with de novo HLA DSA). CONCLUSION One-year protocol biopsies of ABOi and ABOc LD recipients do not differ in chronic changes, inflammation, or SCRs.