Matching in pancreas transplantation--a registry analysis

HLA-B Matching Prolongs Allograft Survival in Islet Cell Transplantation

Islet cell transplantation (ITx) is an effective therapeutic approach for selected patients with type 1 diabetes with hypoglycemia unawareness and severe hypoglycemia events. In organ transplantation, human leukocyte antigen (HLA) mismatching between donor and recipient negatively impacts transplant outcomes. We aimed to determine whether HLA matching has an impact on islet allograft survival. Forty-eight patients were followed up after islet transplantation at our institution from 2000 to 2020 in a retrospective cohort. Patients underwent intrahepatic ITx or laparoscopic omental approach. Immunosuppression was dependent upon the protocol. We analyzed HLA data restricted to A, B, and DR loci on allograft survival using survival and subsequent multivariable analyses. Patients were aged 42.8 ± 8.4 years, and 64.3% were female. Diabetes duration was 28.6 ± 11.6 years. Patients matching all three HLA loci presented longer graft survival (P = 0.030). Patients with ≥1 HLA-B matching had longer graft survival compared with zero matching (P = 0.025). The number of HLA-B matching was positively associated with time of graft survival (Spearman's rho = 0.590; P = 0.034). Analyses adjusted for confounders showed that ≥1 matching for HLA-B decreased the risk of allograft failure (P = 0.009). Our data suggest that HLA-B matching between recipients and donors improved islet allograft survival. Matching all three HLA loci (A, B, and DR) was also associated with prolonged islet allograft survival. Prospective studies and a larger sample size are warranted to validate our findings.

Long-term Persistence of Allosensitization After Islet Allograft Failure

BACKGROUND

Allosensitization has been reported after discontinuation of immunosuppression following graft failure in islet transplantation (ITx) recipients, though duration of its persistence is unknown.

METHODS

We evaluated 35 patients with type 1 diabetes who received ITx, including 17 who developed graft failure (ITx alone, n = 13; ITx plus bone marrow-derived hematopoietic stem cells, n = 4) and 18 with persistent graft function. Panel-reactive antibody (PRA) was measured yearly for the duration of graft function within 1 y after graft failure at enrollment and yearly thereafter.

RESULTS

In ITx alone graft failure patients, 61% (8/13) were PRA-positive at 6 y postgraft failure, and 46% (6/13) developed donor-specific anti-HLA antibodies (DSA to 2 ± 1 donors) during follow-up. The degree of sensitization was variable (cPRA ranging between 22% and 100% after graft failure). Allosensitization persisted for 7-15 y. Three subjects (3/13) were not allosensitized. In ITx plus bone marrow-derived hematopoietic stem cell recipients, cPRA-positivity (88%-98%) and DSA positivity persisted for 15 y in 75% (3/4) of subjects.

CONCLUSIONS

Allosensitization was minimal while subjects remained on immunosuppression, but after discontinuation of immunosuppressive therapy, the majority of subjects (77%) became allosensitized with persistence of PRA positivity for up to 15 y. Persistence of allosensitization in this patient population is of clinical importance as it may result in longer transplant waiting list times for identification of a suitable donor in the case of requiring a subsequent transplant.

First World Consensus Conference on pancreas transplantation: Part II - recommendations

The First World Consensus Conference on Pancreas Transplantation provided 49 jury deliberations regarding the impact of pancreas transplantation on the treatment of diabetic patients, and 110 experts' recommendations for the practice of pancreas transplantation. The main message from this consensus conference is that both simultaneous pancreas-kidney transplantation (SPK) and pancreas transplantation alone can improve long-term patient survival, and all types of pancreas transplantation dramatically improve the quality of life of recipients. Pancreas transplantation may also improve the course of chronic complications of diabetes, depending on their severity. Therefore, the advantages of pancreas transplantation appear to clearly surpass potential disadvantages. Pancreas after kidney transplantation increases the risk of mortality only in the early period after transplantation, but is associated with improved life expectancy thereafter. Additionally, preemptive SPK, when compared to SPK performed in patients undergoing dialysis, appears to be associated with improved outcomes. Time on dialysis has negative prognostic implications in SPK recipients. Increased long-term survival, improvement in the course of diabetic complications, and amelioration of quality of life justify preferential allocation of kidney grafts to SPK recipients. Audience discussions and live voting are available online at the following URL address: http://mediaeventi.unipi.it/category/1st-world-consensus-conference-of-pancreas-transplantation/246.

Survival benefit of the homologous kidney allograft in simultaneous pancreas-kidney transplants and its potential protective role

The superior death-censored graft survival of the pancreas allograft in simultaneous pancreas kidney transplants (SPK) over pancreas alone transplants (PTA) has long been recognized. Using data from the Scientific Registry of Transplant Recipients (SRTR) and a high-volume pancreas transplant program, we investigated the possible protective role of the kidney allograft in SPK transplants. We analyzed 19,043 primary pancreas transplants between 2000 and 2020, including 735 transplants performed at the University of Minnesota. SPK transplants demonstrated a superior death-censored graft survival over pancreas after kidney (PAK) and simultaneous pancreas and living donor kidney (SPLK) transplants, which both demonstrated better survival than PTA transplants. This effect was not affected by mode or duration of renal replacement therapy prior to transplant. Furthermore, we found that HLA match at the B-locus between the prior kidney and current pancreas allografts demonstrated a protective effect (HR 0.54; 95% confidence interval 0.29-1.00), with a 2-antigen match demonstrating superior death-censored graft survival to a 1- or 0-antigen match. We propose that a homologous kidney allograft in SPK transplants affords protection to the pancreas allograft - likely through a combination of better surveillance for rejection and direct immunoprotection offered by the same-donor kidney. This article is protected by copyright. All rights reserved.

HLA-A, -B, -C, -DR, and -DQ Matching in Pancreas Transplantation: Effect on Graft Rejection and Survival

To enhance selection of appropriate deceased donors for pancreas transplants, we sought to determine whether HLA matching improved posttransplantation outcomes. In this single-center study of 1219 pancreas transplants, we correlated posttransplantation outcomes with HLA-A, -B, -C, -DR, and -DQ matches and mismatches. Rejection was linearly correlated with the number of mismatches. The individual number of HLA mismatches reached significance at four or more with a 2.3- to 2.9-fold increase in rejection. The effect was most predominant with HLA-B (1.8-fold with one mismatch and 2.0-fold with two mismatches) and -DR (1.9-fold with two mismatches) loci, whereas HLA-A, -C, and -DQ matches or mismatches did not independently predict acute rejection. The affect was strongest in solitary pancreas transplants, with little impact for simultaneous pancreas and kidney (SPK). In contrast, HLA matching did not affect graft or patient survival rates but was associated with a reduced risk of opportunistic infection. Avoidance of acute rejection saved an estimated $32 000 for solitary pancreas recipients and $52 000 for SPK recipients in hospital costs. Our data do not support the use of HLA matching for predicting pancreas graft survival but do support its significance for the reduction of acute rejection, particularly for solitary pancreas recipients.

Tolerogenic protocols for intestinal transplantation

The intestine has long been considered as a "forbidden" organ to transplant [Ann. Surg. 216 (1992) 223-33]. This is due to the particularly challenging nature of the immunological conflict that an intestinal graft may cause: a particularly vigorous rejection response, in addition to the capacity to mount a graft-versus-host disease (GVHD) [Transplantation 37 (1984) 429]. Currently, the short-term success of intestinal transplantation (Itx) depends upon the chronic delivery of profound immunosuppression but this causes infection, malignancies--in particular posttransplant lymphoproliferative disorder (PTLD)--and direct drug toxicity. For these reasons, the results of Itx remain inferior to those of other solid organ transplants in the middle and in the long term (Intestinal Transplant Registry: www.small-bowel-transplant.org). Improved results and wider application of Itx requires the development of protocols that would facilitate acceptance of the new intestine thereby allowing to reduce the need for immunosuppression with its attending complications. Relevant experimental data and the recent evolution in the clinical strategies used to promote acceptance of intestinal grafts are reviewed.