Detection of donor-specific anti-HLA antibodies with flow cytometry in eluates and sera from renal transplant recipients with chronic allograft nephropathy1

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Abstract
Background. Chronic allograft nephropathy (CAN), which remains the main cause of graft loss after kidney transplantation, is still poorly understood. Because anti-HLA antibodies may be involved in the pathogenesis of CAN, this study was performed to look for donor-specific antibodies (DSA) fixed onto renal transplants with CAN. Methods. DSA were identified after elution with flow cytometric assay and/or flow cytometric crossmatches in 20 transplants removed after irreversible graft failure caused by CAN and in control samples from 2 transplants with relapsing glomerulopathy, 2 transplants lost after vascular thrombosis, and 4 normal kidneys. The results were compared with those obtained in the serum samples 1 year after grafting, at the time of transplantectomy, and within 2 months after transplantectomy. Results. IgG anti-class I, anti-class II, or both DSA were identified in 70.6% of eluates versus 73.6% of posttransplantectomy serum samples (NS), 42.1% of 1-year postgrafting serum samples (P P <0.05). Our data show a good correlation between the target of anti-HLA antibodies found in both eluates and posttransplantectomy serum samples, but the precise specificity of anti-HLA antibodies is more often assigned in posttransplantectomy serum samples than in eluates. This problem needs further evaluation. Conclusion. This study shows that testing for anti-HLA DSA in eluates from removed kidney transplants using flow cytometry can be achieved and is highly efficient. It already suggests that both anti-class I and anti-class II HLA antibodies can be involved in CAN. Further studies are now needed to evaluate the possibility of identifying such antibodies in the eluates of transplant biopsy specimens from recipients experiencing CAN.