Donor-specific HLA antibodies in chronic renal allograft rejection: a prospective trial with a four-year follow-up.

A total of 1,043 serum samples of kidney allograft recipients with functioning grafts at a mean of 6 years after transplantation were tested once for HLA abs and monitored for graft and patient survival for 4 years after testing. All grafts were transplanted between 1984 and 2004 at the Charité hospital (Berlin, Germany). 1. To our knowledge this is the first study with more than 1,000 patients designed to elucidate the impact of DSA and NDSA on late renal graft outcome. True donor specificity of HLA abs in 30% of antibody positive patients was determined by using a single HLA antigen coated bead assay. 2. The long-term graft survival was adversely impacted by the presence of HLA abs directed against mismatched HLA antigens and to a lesser extent also by NDSA. This difference was shown to be leveled at late stages of graft damage, suggesting NDSA as a predictor of adsorbed DSA killing the graft. 3. The deleterious effect of preexisting and de novo formed HLA abs on long-term graft function was shown to be equal. Despite a negative crossmatch at the time of transplantation sensitized recipients and those who produced HLA abs de novo posttransplant showed the same increased risk of late graft failure. 4. Among patients with DSA and additional NDSA the majority of 74% of assigned potential HLA class I epitopes were shared among DSA and NDSA suggesting mismatched donor antigens as the cause of detected NDSA.