Antibody Monitoring in Pancreas Transplantation: When should we do protocol biopsies?

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IntroductionIn kidney transplantation de novo donor-specific HLA antibodies (DSA) have been found to correlate to poor graft survival and Consensus Guidelines recommend a protocol biopsy. In pancreas transplantation DSA had also been associated with poor graft outcomes however there are no recommendations on protocol biopsies. In June, 2013 a screening protocol was initiated for detection of anti-HLA antibodies (Abs) by Luminex. Testing was performed on patients presenting with dysfunction and by protocol at 0, 3, 6, 12 months and yearly for new transplants and yearly for previous transplants. Patients with DSA Abs and patients with high MFI non-DSA Abs were considered for protocol biopsy of both organs.ResultsDuring the study period 144 pancreas transplant recipients were screened for anti-HLA antibodies. 106 patients had initially negative antibodies and 20 among them produced de novo antibodies. 38 had positive antibodies at the initial testing.86 patients had negative antibodies though the study period. Among them 10 presented dysfunction and biopsy proven rejection of either organ during follow-up, being 8 acute cellular rejections (ACR) and 2 antibody mediated rejections (AMR).There were 20 patients with initially negative Abs that presented de novo Abs during follow up. Seven of these were found to have positive Abs when presenting with rejection (all non-DSA Abs). The other 13 cases were detected by screening. Among these, there were 7 non-DSA and 6 DSA cases. No biopsies were performed in the non-DSA cases with 1 presenting rejection at 3 years of follow-up. All 6 patients with DSA Abs had protocol biopsies with 2 of them showing subclinical kidney AMR.We found 38 patients with positive Abs at the initial testing. 10 of them were detected when presenting with dysfunction and all were biopsied. Among these, 5 had DSA and 5 non-DSA Abs and all but one patient had rejection. The other 28 cases were detected by screening. In this group, 18 patients had non-DSA Abs and 8 of them were biopsied with negative results and remained rejection free. The last 10 cases had DSA Abs initially. Six of them were biopsied and had subclinical rejection on the kidney (3), the pancreas (1) or both (2). Of the remaining four patients without biopsy, 2 presented kidney humoral rejection during at 6 and 12 months of follow-up and 2 remained rejection free.DiscussionOur protocol detected 40% of patients with positive anti-HLA Abs (26% at the initial testing and 14% de novo during follow-up) with 36% of them being DSA abs. In non-dysfunctioned patients with non-DSA abs protocol biopsies were negative in all biopsied patients and only 4% of them presented rejection during follow-up. In contrast, in non-dysfunctioned patients with DSA abs protocol biopsies found subclinical rejection in 66% of them and half the non-biopsied patients presented rejection during follow-up. We conclude that patients with DSA abs may benefit from protocol biopsies of both grafts.

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