De novo donor‐specific anti‐HLA antibodies after kidney transplantation are associated with impaired graft outcome independently of their C1q‐binding ability

Summary Many aspects of post‐transplant monitoring of donor‐specific (DSA) and non‐donor‐specific (nDSA) anti‐HLA antibodies on renal allograft survival are still unclear. Differentiating them by their ability to bind C1q may offer a better risk assessment. We retrospectively investigated the clinical relevance of de novo C1q‐binding anti‐HLA antibodies on graft outcome in 611 renal transplant recipients. Acute rejection (AR), renal function, and graft survival were assessed within a mean follow‐up of 6.66 years. Post‐transplant 6.5% patients developed de novo DSA and 11.5% de novo nDSA. DSA (60.0%; P < 0.0001) but not nDSA (34.1%, P = 0.4788) increased rate of AR as compared with controls (27.4%). C1q‐binding anti‐HLA antibodies did not alter rate of AR in both groups. Renal function was only significantly diminished in patients with DSAC1q+. However, DSA significantly impaired 5‐year graft survival (65.2%; P < 0.0001) in comparison with nDSA (86.7%; P = 0.0054) and controls (90.7%). While graft survival did not differ between DSAC1q− and DSAC1q+ recipients, 5‐year allograft survival was reduced in nDSAC1q+ (80.9%) versus nDSAC1q− (90.7%, P = 0.0251). De novo DSA independently of their ability to bind C1q are associated with diminished graft survival.