Donor-specific sensitization by cadaveric venous allografts used for arterial reconstruction in peripheral arterial occlusive vascular disease

Immunological Aspects Involved in the Degeneration of Cryopreserved Arterial Allografts

Introduction: Cryopreserved arterial allografts have remained an option in patients requiring distal revascularization or associated with vascular infection, in the absence of a valid autogenous saphenous vein. The objective of this study is to describe the different clinical, anatomopathological, and immunological findings related to vascular transplant rejection.

Methods: In a prospective trial, 35 patients who underwent cryopreserved allogeneic arterial bypass were studied, including demographics and conduit patency. Anti-HLA antibody production was stablished prior to the surgery, 7 days, 1, 3 months, and every 3 months since. Clinical and ultrasound evaluation was added after the first month. Donor HLA-typing was retrieved whenever available, allowing for the characterization and quantification of donor specific antibodies. Cytotoxic crossmatch test was also performed. A second group of patients with allograft degenerations registered during the follow up period was studied. In this group, exclusively for aneurysm description and histopathological analysis, they were included those degenerated vascular transplants from the original series, but also those implanted prior to the beginning of the study and degraded during follow up.

Results: All patients studied displayed an increase in anti-HLA antibodies one month after the intervention, regarding bypass patency. In total, 14 patients fulfilled requirements for the study of donor specific antibodies, equally showing IgG production detectable one month after surgery. The presence of complement-fixing antibodies was also confirmed. Antibody levels were not related to graft degeneration. No specific immune markers able to predict aneurysmal development and evolution were found. From the original group, 3 patients suffered aneurysmal degeneration during follow up, together with 9 bypasses previously implanted. Average time until the first degeneration was 33 ± 19.7 months, with 30.6 ± 17.7 and 54.5 ± 2.5 months for a second and third degeneration, when occurring. Therefore, subsequent vascular transplants frequently augmented the time for new degenerations, despite increasing sensibilization. Samples from eight degenerated allografts were available for analysis, unexpectedly showing inflammatory infiltrate in only four cases and immune complex deposition in 7.

Conclusions: Immune response against vascular transplants was confirmed in all cases, but chronic rejection did not necessarily provoke bypass degradation or reduced the time for new aneurysms to develop in subsequent allografts.

Third-party vessel allografts in kidney and pancreas transplantation: Utilization, de novo DSAs, and outcomes

Third-party vascular allografts (VAs) are an invaluable resource in kidney and pancreas transplantation when vascular reconstruction is needed and additional vessels from the organ donor are not available. We report the largest single-center experience to date on VA use, at a high-volume U.S. transplant center. Over a 7-year period, VAs were used for vascular reconstruction of 65 kidneys and 5 pancreases, in 69 recipients. The renal vein required reconstruction more often with right kidney transplantation (72.5% vs 27.5%, P < .001), and the renal artery required reconstruction more often with left kidney transplantation (67.6% vs 32.4%, P = .003). Eleven patients (15.9%) developed anti-VA de novo HLA donor-specific antibodies (dnDSAs) at a median time after transplantation of 19.0 months. Higher number of HLA mismatches between the VA donor and the recipient, and development of anti-organ allograft dnDSAs were significant predictors of anti-VA dnDSA development. Those with anti-VA dnDSAs had a higher rate of organ allograft rejection (45.4% vs 13.8%, P = .03) compared to those without, but there was no significant difference in incidence of vascular complications or graft outcomes. VAs can help circumvent challenging surgical situations. Anti-VA dnDSAs do not adversely affect organ allograft outcomes; however, they can contribute to HLA sensitization in the recipients.

Non-HLA-matched 3rd party vascular allograft in renal transplant may lead to sensitization against donor HLA

3rd party donor vessels are often used for vascular reconstruction in organ transplantation. While current practice ensures that 3rd party vessels are blood group matched, HLA matching to the non-intended recipient is not performed. This practice potentially sensitizes the recipient and may reduce their future chance of renal transplant from a larger pool of donors. We examined our cohort of renal transplant recipients who received non-HLA-matched 3rd party vessels for the de-novo development of donor-specific HLA antibodies. Our institution's Human Tissue Authority (HTA) blood vessel registers were examined to identify stored donor vessels and their non-intended recipients. Donor vessel HLA status was cross-referenced with the recipient HLA status. Between 2004 and 2014, five patients were identified that received 3rd party non-HLA-matched vessels for vascular reconstruction during renal transplantation. Three patients (60%) subsequently developed donor-specific HLA antibodies. These data provide evidence that use of non-HLA-matched stored 3rd party vascular grafts may lead to sensitization in the recipient. Where time permits, HLA matching should be performed to avoid this allogeneic response. Laboratories monitoring DSA should be aware of any patient receiving a non-HLA-matched 3rd party vascular graft, and recipients may benefit from increased post-transplant immunological vigilance.

Cold-stored cadaveric venous allograft for superior mesenteric/portal vein reconstruction during pancreatic surgery

BACKGROUND

SMV/PV resection has become common practice in pancreatic surgery. The aim of this study was to evaluate the technical feasibility and surgical outcome of using cold-stored cadaveric venous allografts (AG) for superior mesenteric vein (SMV) and portal vein (PV) reconstruction during pancreatectomy.

METHODS

Patients who underwent pancreatic resection with concomitant vascular resection and reconstruction with AG between January 2006 and December 2014 were identified from our institutional prospective database. Medical records and pre- and postoperative CT-images were reviewed.

RESULTS

Forty-five patients underwent SMV/PV reconstruction with AG interposition (n = 37) or AG patch (n = 8). The median operative time and blood loss were 488 min (IQR: 450-551) and 900 ml (IQR: 600-2000), respectively. Major morbidity (Clavien ≥ III) occurred in 16 patients. Four patients were reoperated (thrombosis n = 2, graft kinking/low flow n = 2) and in-hospital mortality occurred in two patients. On last available CT scan, 3 patients had thrombosis, all of whom also had local recurrence. Estimated cumulative patency rate (reduction in SMV/PV luminal diameter <70% and no thrombosis) at 12 months was 52%.

CONCLUSION

Cold-stored cadaveric venous AG for SMV/PV reconstruction during pancreatic surgery is safe and associated with acceptable long-term patency.

Donor-specific anti-HLA antibodies after bone-graft transplantation. Impact on a subsequent renal transplantation: a case report

Immunological evaluation by panel-reactive antibody (PRA) and determination of anti-HLA specificity are important phases in the evaluation of patients awaiting kidney transplantation. The main causes of immunization are previous solid organ transplantation, hemotransfusion, and pregnancy. It is also possible that immunogenicity can be triggered by vascularized tissue grafts. Immune induction by cryopreserved bone prostheses is not yet understood. A 19-year-old patient with osteosarcoma had undergone resection of the left proximal tibia with reconstruction using human bone in 1997. The donor HLA typing was as follows: A3, A29 (19); B44 (12), Bw4; DR13 (6), DR7, DR52, DR53. The patient was subsequently enrolled onto the waiting list for cadaveric donor kidney transplantation due to chronic kidney failure caused by cisplatin toxicity. Pretransplantation immunological screening using the complement-dependent cytotoxicity (CDC) technique revealed a PRA of 63%. IgG antibody specificities were detected against class I and class II donor antigens, specifically anti-A3, B44, DR7 antibodies, using flow cytometry (Tepnel Luminex). Further immunological studies using single HLA specificity analysis (LSA Class I degrees -II degrees , Tepnel-Luminex) showed direct antibodies against all donor antigen specificities. This case showed immune induction after the implantation of bone prosthesis in a kidney transplant candidate, underlining the importance of the availability of HLA typing data of donors of a human prosthesis.

Antibody-mediated rejection of arterialised venous allografts is inhibited by immunosuppression in rats

Objectives and Design

We determined in a rat model (1) the presence and dynamics of alloantibodies recognizing MHC complexes on quiescent Brown-Norway (BN) splenic cells in the sera of Lewis (LEW) recipients of Brown-Norway iliolumbar vein grafts under tacrolimus immunosuppression; and (2) the presence of immunoglobulins in the wall of acute rejected vein allografts.

Materials and Methods

Flow cytometry was used for the analysis of day 0, 14 and 30 sera obtained from Lewis recipients of isogeneic iliolumbar vein grafts (group A) or Brown-Norway grafts (group B, C) for the presence of donor specific anti-MHC class I and II antibodies. Tacrolimus 0.2 mg/kg daily was administered from day 1 to day 30 (group C). Histology was performed on day 30.

Results

Sera obtained preoperatively and on day 30 were compared in all groups. The statistically significant decrease of anti MHC class I and II antibody binding was observed only in allogenic non-immunosuppressed group B (splenocytes: MHC class I - day 0 (93%±7% ) vs day 30 (66%±7%), p = 0.02, MHC class II - day 0 (105%±3% ) vs day 30 (83%±5%), p = 0.003; B-cells: MHC class I - day 0 (83%±5%) vs day 30 (55%±6%), p = 0.003, MHC class II - day 0 (101%±1%) vs day 30 (79%±6%), p = 0.006; T-cells: MHC class I - day 0 (71%±7%) vs day 30 (49%±5%), p = 0.04). No free clusters of immunoglobulin G deposition were detected in any experimental group.

Conclusion

Arterialized venous allografts induce strong donor-specific anti-MHC class I and anti-MHC class II antibody production with subsequent immune-mediated destruction of these allografts with no evidence of immunoglobulin G deposition. Low-dose tacrolimus suppress the donor-specific antibody production.

Presensitization revisited: pitfalls of vascular allografts in transplant candidates

Vascular allografts in end-stage renal disease (ESRD) patients represent a particular immunological challenge. A broad HLA immunization led us to study in depth the history of two patients with vascular allografts. In Case 1 the allograft was added to a Gore-Tex graft used for haemodialysis access and no immunosuppression was administered. In Case 2 the allograft was used to prolong a renal artery from living donor and immunosuppression was suboptimal. In vascular surgery, immunosuppression is mainly used to improve graft patency. ESRD patients are potential organ recipients and immunosuppression should therefore be tailored to reduce HLA immunization.

The positive effect of immunosuppression on adaptation of venous allografts to arterialisation in rats

OBJECTIVES AND DESIGN

We investigated whether immunosuppression was necessary for transplanted allogeneic veins to adapt to arterialisation. We used a transplant rat model with or without immunosuppression.

MATERIAL AND METHODS

Iliolumbar veins from Lewis (LEW) or Brown-Norway (BN) rats were transplanted into the abdominal aorta of isogeneic (LEW to LEW; group A) or allogeneic (BN to LEW; groups B and C) rats. Group C had daily intramuscular injections of 0.2mgkg(-1) FK506. Light microscope evaluations of grafts were performed at 30 days following transplantation. We determined the presence of endothelial cells, the intensity of intimal proliferation and the degree of infiltration by Lewis major histocompatibility complex (MHC) class II positive, CD4-positive and CD8-positive cells into the adventitia.

RESULTS

Groups A and C displayed similar results in intimal thickness (12.7+/-7.0microm vs. 15.0+/-8.4 mum, respectively) and degree of adventitial infiltration by MHC class II positive (16.6+/-7.5 vs. 14.6+/-6.2, respectively), CD8-positive (0.8+/-1.7 vs. 1.8+/-2.6, respectively) and CD4-positive (12.5+/-7.7 vs. 5.8+/-4.6, respectively) cells. In contrast, allogeneic rats without immunosuppression (group B) showed infiltration of host immunocompetent cells and destruction of the venous wall with no histological signs of arterialisation.

CONCLUSION

Immunosuppressive therapy is necessary for venous allograft adaptation to arterialisation in rats.