Few studies have evaluated the role of donor-specific antibodies(DSA) in pancreas transplantation(PT). The aim of this study was to analyze the incidence of DSA pre and post-PT and outcomes in a protocol of routine DSA monitoring.

From march/2018 to December/2020, 170 technical successful PT, being 94 SPK and 76 solitary PT(S-PT), of which 65 PAK and 11 PTA, were followed for detection of post-transplant(PO) DSA. All PT were performed by a systemic(cava)-enteric drainage with a negative virtual crossmatch(assuming MFI >1500 as cutoff) and receiving induction therapy with Thymoglobulin(5mg/kg for SPK and 7mg/kg for S-PT), tacrolimus, mycophenolate sodic and steroids. Screening of HLA-antibodies was performed by Luminex at 3,6 and 12 months PO or when a rejection episode occurred and twice a year thereafter for all S-PT. The same DSA monitoring was performed for selected SPK recipients with a cPRA>0 or when a rejection occurred. Any DSA with value > 500 MFI was registered. All kidney or pancreas rejection was biopsy-proven and stained for C4d. Pre-transplant cPRA was negative in 77(82%) of SPK and 59(78%) of S-PT recipients. Pretransplant DSAs were found in 1 SPK and 4 S-PT recipients, all < 1500 of MFI. The prevalence of de Novo DSA was significantly higher among S-PT ,17(22.3%), compared to SPK recipients,7(7.4%),p<0.005. Among DSA+ patients, all SPK and 9(53%) S-PT recipients presented MFI>1500. The average time of DSA appearance was 8.3 months(3-28) and most of them,19(79%), were triggered after a rejection episode. Overall, more rejection episodes were observed in patients with DSA+ than in DSA - (83% x 29%, p<0.001,OR=11.9). Among DSA+ S-PT patients, rejection occurred in 13(76%) , being 10(77%) a confirmed or suspected antibody-mediated rejection(AMR). Similarly, the presence of C4d+ in pancreas graft biopsies was higher among DSA+ S-PT(35.3% x 5.1%,p=0.001) as was the rate of immunological graft loss for DSA+ SPK (28% x 2.3%,p=0.001,OR=17.0) and DSA+ S-PT recipients(47% x 10%,p=0.001, OR=7.8). 1-Year and long-term patient survival was similar between S-PT or SPK DSA+ and DSA- groups while 1-year(65% x 95%, p=0.002) and long-term(53% x 83%, p=0.01) pancreas survival was significantly lower for DSA+ S-PT patients. Interestingly, long-term pancreas graft survival among S-PT patients was comparable between “weak”DSA+(MFI<1500) and DSA- (87% x 83%, respectively) and the latter were significantly higher than DSA+(MFI>1500) S-PT(22%, p<0.001) patients.

Occurrence of post-transplant DSA was higher in S-PT than in SPK recipients, commonly triggered after a rejection episode. De novo DSA was strongly related to higher rate of rejections, AMR, C4d+ pancreatic biopsies, immunological graft failures and inferior pancreas graft survival, particularly if MFI>1500. A protocol of routine DSA monitoring could improve diagnosis and interventioning for immunological events after PT.