#6440 c1q-binding anti-hla donor-specific antibodies and long-term kidney graft outcomes

Abstract Background and Aims Immunological response mediated by anti-HLA donor specific antibodies plays an important role in renal allograft injury in kidney transplant recipients. Several characteristics of donor-specific antibodies such as HLA class, specificity, mean fluorescence intensity, IgG subclass and C1q-binding capacity can be assessed. The aim of this study was to determine the impact of circulating anti-HLA donor-specific and their characteristics, including C1q-binding capacity, on long-term kidney graft outcomes. Method One hundred eight patients from our transplant center, who underwent kidney allograft biopsy within three to twenty-four months after renal transplantation from brain-dead deceased donor between 2018 and 2020, were included in the study. At the time of biopsy patients’ sera were collected and stored for analysis. Samples were tested for anti-HLA donor-specific antibodies and their characteristics. Antibodies with mean fluorescence intensity > 500 were considered positive. Results Median time of follow-up of patients was thirty-nine months. Out of nineteen patients with detected donor-specific antibodies, ten patients were identified with immunodominant donor-specific antibodies with C1q-binding capacity (out of them, six patients had anti-HLA donor-specific antibodies detected also before transplantation). C1q-binding antibodies were IgG1 (six patients), IgG3 (three patients) and IgG1+IgG3 (one patient). Presence at the time of biopsy of donor-specific antibodies and their C1q-binding capacity were independent predictors (HR = 5.13, p < 0.001 and HR = 14.64, p < 0.001; respectively) of inferior kidney graft outcomes (composite of 30% reduction from eGFR at biopsy or death-censored graft loss). Conclusion Detection of donor-specific antibodies and their C1q-binding capacity might provide prognostic information in post-transplant monitoring in kidney transplant recipients.