Banff schema for grading pancreas allograft rejection: working proposal by a multi-disciplinary international consensus panel

Predicted Indirectly Recognizable T-cell Epitope (PIRCHE) Load Correlates With Rejection Events After Simultaneous Pancreas-Kidney Transplantation

Background

Given the lack of specificity of current blood and urine testing and the resistance/inability to perform pancreas allograft biopsies, additional noninvasive investigational tools to assess the risk for rejection are needed. This study examines the clinical impact of molecular HLA matching in a large single-center simultaneous pancreas-kidney (SPK) transplant program.

Methods

The study cohort comprised 238 SPK recipients between 2012 and 2021. The number of HLA mismatches, eplet, Snow (that counts the number of protein-specific surface-accessible donor HLA amino acid mismatches), and predicted indirectly recognizable T-cell epitope (PIRCHE, version 4.2; 100%) loads were calculated on the basis of 2-field HLA-A, -B, -C, -DRB1, and -DQB1 typing of recipients and donors. Univariable and multivariable Cox proportional hazard, as well as Kaplan-Meier analyses, were performed considering either first rejection events of a graft or a composite endpoint of de novo donor-specific antibodies, first rejection, and uncensored graft failure of either organ.

Results

Kaplan-Meier analyses considered class II PIRCHE groups separated by a threshold of 7. From the considered histocompatibility metrics, multivariable regression analysis revealed only PIRCHE-II derived from donor HLA class II as statistically significantly correlated with clinical events and rejection after SPK, mostly driven by pancreas rejections. Furthermore, longer dialysis time and the induction agent had significant negative impacts on the defined composite endpoint.

Conclusions

Our data support the clinical benefit of incorporating PIRCHE scores for the interpretation of class II HLA mismatches among patients undergoing SPK transplantation.

Gene expression-based molecular scoring of pancreas transplant rejection for a quantitative assessment of rejection severity and resistance to treatment

Pancreas transplantation improves glycemic control and mortality in patients with diabetes but requires aggressive immunosuppression to control the alloimmune and autoimmune response. Recent developments in "omics" methods have provided gene transcript-based biomarkers for organ transplant rejection. The tissue Common Response Module (tCRM) score is developed to identify the severity of rejection in kidney, heart, liver, and lung transplants. Still, it has not yet been validated in pancreas transplants (PT). We evaluated the tCRM score's relevance in PT and additional markers of acute cellular rejection (ACR) for PT. An analysis of 51 pancreas biopsies with ACR identified 37 genes and 56 genes significantly upregulated in the case of grade 3 and grade 2 ACR, respectively (P < .05). Significant differences were seen with higher grades of rejection among several transcripts. Of the 22 genes differentially expressed in grade 3 ACR, 18 were also differentially expressed in grade 2 ACR. The rejection signal was attributable to activated leukocytes' infiltration. Significantly higher tCRM scores were found in grade 3 ACR (P = .007) and grade 2 ACR (P = .004), compared to normal samples. The tCRM score was able to distinguish treatment-resistant cases from those successfully treated for rejection.

Risk Factors for Early Post-transplant Weight Changes Among Simultaneous Pancreas-kidney Recipients and Impact on Outcomes

Background

There are limited data about the risk factors for weight changes and the association of significant weight changes with graft and metabolic outcomes after simultaneous pancreas and kidney (SPK) transplantation.

Methods

We included all SPK recipients with both allografts functioning for at least 6 mo post-transplant and categorized them based on the weight changes from baseline to 6 mo post-transplant. We analyzed risk factors for significant weight gain (SWG) and significant weight loss (SWL) over 6 mo post-transplant, as well as outcomes including pancreas uncensored graft failure, pancreas death-censored graft failure (DCGF), composite pancreas graft outcomes of DCGF, use of an antidiabetic agent, or hemoglobin A1C >6.5%, and kidney DCGF.

Results

Of 280 SPK recipients, 153 (55%) experienced no significant weight change, 57 (20%) SWG, and 70 (25%) SWL. At 6 mo post-transplant, mean weight changes were 1.2% gain in the no significant weight change group, 13.4% gain in SWG, and 9.6% loss in the SWL groups. In multivariate analysis, the only factor associated with decreased risk for weight gain was older recipient age (aOR, 0.97; 95% confidence intervals, 0.95-0.99). Importantly, SWG or SWL were not associated with pancreas graft failure, P-DCGF, or K-DCGF. Interestingly in the adjusted model, SWG at 6 mo was associated with a lower risk for composite outcomes (HR, 0.35; 95% confidence intervals, 0.14-0.85).

Conclusions

Forty-five percent of SPK recipients had significant weight changes by 6 mo post-transplant, but only 20% exhibited SWG. Likely because of proper management, weight changes were not associated with poor outcomes post-SPK transplant.

Subclinical Pancreas Rejection on Protocol Biopsy Within the First Year of Simultaneous Pancreas Kidney Transplant

This single-center retrospective study investigated subclinical rejection prevalence and significance in simultaneous pancreas and kidney transplant (SPKT) recipients. We analyzed 352 SPKT recipients from July 2003 to April 2022. Our protocol included pancreas allograft surveillance biopsies at 1, 4, and 12months post-transplant. After excluding 153 patients unable to undergo pancreas biopsy, our study cohort comprised 199 recipients. Among the 199 patients with protocol pancreas biopsies, 107 had multiple protocol pancreas biopsies in the first year, totaling 323. Subclinical rejection was identified in 132 episodes (41%). Of these, 72% were Grade 1, 20% were indeterminate, and 8% were Banff Grade 2 or higher. All episodes of subclinical rejection were treated. Rates of pancreas graft loss (10% vs. 7%) and clinical rejection (21% vs. 20%) at 3 years were similar between those with and without subclinical rejection. Subclinical rejection Banff Grade 2 or more was associated with poor pancreas graft survival HR of 5.5 (95% CI: 1.24-24.37, p = 0.025). Of 236 simultaneous protocol kidney and pancreas biopsies, 102 (43%) showed pancreas subclinical rejection, while only 17% had concurrent kidney subclinical rejection. Our findings suggest limited predictive value of pancreatic enzymes and euglycemia in detecting pancreas rejection. Furthermore, poor concordance existed between pancreas and kidney subclinical rejection.

Accessibility of Percutaneous Biopsy in Retrocolic-Placed Pancreatic Grafts With a Duodeno-Duodenostomy

Duodeno-duodenostomy (DD) has been proposed as a more physiological alternative to conventional duodeno-jejunostomy (DJ) for pancreas transplantation. Accessibility of percutaneous biopsies in these grafts has not yet been assessed. We conducted a retrospective study including all pancreatic percutaneous graft biopsies requested between November 2009 and July 2021. Whenever possible, biopsies were performed under ultrasound (US) guidance or computed tomography (CT) guidance when the US approach failed. Patients were classified into two groups according to surgical technique (DJ and DD). Accessibility, success for histological diagnosis and complications were compared. Biopsy was performed in 93/136 (68.4%) patients in the DJ group and 116/132 (87.9%) of the DD group (p = 0.0001). The graft was not accessible for biopsy mainly due to intestinal loop interposition (n = 29 DJ, n = 10 DD). Adequate sample for histological diagnosis was obtained in 86/93 (92.5%) of the DJ group and 102/116 (87.9%) of the DD group (p = 0.2777). One minor complication was noted in the DD group. The retrocolic position of the DD pancreatic graft does not limit access to percutaneous biopsy. This is a safe technique with a high histological diagnostic success rate.

Banff 2022 pancreas transplantation multidisciplinary report: Refinement of guidelines for T cell-mediated rejection, antibody-mediated rejection and islet pathology. Assessment of duodenal cuff biopsies and noninvasive diagnostic methods

The Banff pancreas working schema for diagnosis and grading of rejection is widely used for treatment guidance and risk stratification in centers that perform pancreas allograft biopsies. Since the last update, various studies have provided additional insight regarding the application of the schema and enhanced our understanding of additional clinicopathologic entities. This update aims to clarify terminology and lesion description for T cell-mediated and antibody-mediated allograft rejections, in both active and chronic forms. In addition, morphologic and immunohistochemical tools are described to help distinguish rejection from nonrejection pathologies. For the first time, a clinicopathologic approach to islet pathology in the early and late posttransplant periods is discussed. This update also includes a discussion and recommendations on the utilization of endoscopic duodenal donor cuff biopsies as surrogates for pancreas biopsies in various clinical settings. Finally, an analysis and recommendations on the use of donor-derived cell-free DNA for monitoring pancreas graft recipients are provided. This multidisciplinary effort assesses the current role of pancreas allograft biopsies and offers practical guidelines that can be helpful to pancreas transplant practitioners as well as experienced pathologists and pathologists in training.

Ultrasound of pancreatic transplant complications: a primer for radiologists

Pancreatic transplantation is an established treatment for patients with type 1 diabetes patients and select type 2 diabetes patients, with excellent survival rates as graft health is evaluated through regular imaging and early detection of complications. Amongst the various imaging methods that may aid in diagnosis of pancreatic transplant complications, ultrasound is a widely available, quick, portable, and cost-effective technique, often used as the sole method to assess for pancreatic transplant complications. When assessing a patient with a pancreatic transplant, the radiologist should be methodical in assessing the vasculature, the pancreatic parenchyma, and the peripancreatic regions. Complications can be categorised based on time from transplant and type of complications, and include vascular, parenchymal, and enteric/anastomotic complications. Doppler has a major role in the diagnosis of vascular complications including arterial and venous thrombosis, arterial stenosis, pseudoaneurysms, and haematomas. Pancreatic complications include rejections and pancreatitis, and are often diagnosed through a combination of clinical, laboratory, and imaging findings, such as pancreatic heterogeneity or the presence of pancreatic pseudocysts. Enteric/anastomotic complications include leaks and bowel obstructions, and may require cross-sectional imaging in addition to ultrasound. This review covers the most common and high-impact vascular, parenchymal, and enteric/anastomotic complications that should be considered in every radiologist's search pattern when assessing a pancreatic graft, as well as their respective postoperative timeframes.

Favorable outcomes in Hispanic recipients receiving simultaneous pancreas kidney transplantation

The objective of this study was to compare the long-term outcomes of Hispanic versus white recipients who underwent simultaneous pancreas kidney transplantation (SPKT). This single-center study, conducted from 2003 to 2022, had a median follow-up of 7.5 years. The study included 91 Hispanic and 202 white SPKT recipients. The mean age (44 vs. 46 years), percentage of males (67% vs. 58%), and body mass index (BMI) (25.6 vs. 25.3 kg/m2 ) were similar between the Hispanic and white groups. The Hispanic group had more recipients with type 2 diabetes (38%) compared to the white group (5%, p < .001). The duration of dialysis was longer in Hispanics (640 vs. 473 days, p = .02), and fewer patients received preemptive transplants (10% vs. 29%, p < .01) compared to whites. Hospital length of stay, rates of BK Viremia, and acute rejection episodes within 1 year were similar between the groups. The estimated 5-year kidney, pancreas, and patient survival rates were also similar between the groups, 94%, 81%, and 95% in Hispanics, compared to 90%, 79%, and 90% in whites. Increasing age and longer duration of dialysis were risk factors for death. Although Hispanic recipients had a longer duration on dialysis and fewer preemptive transplants, the survival rates were similar to those of white recipients. However, referring providers and many transplant centers continue to overlook pancreas transplants for appropriately selected patients with type 2 diabetes, particularly among minority populations. As a transplant community, it is crucial that we make efforts to comprehend and tackle these obstacles to transplantation.

Analysis of Individual Components of Frailty in Simultaneous Pancreas and Kidney, and Solitary Pancreas Transplant Recipients

Backgrounds

It is not known which of the 5 components of the Fried frailty score have the most predictive value for outcomes in simultaneous pancreas-kidney transplant (SPK) and solitary pancreas transplant (SPT) recipients.

Methods

In this study, we sought to investigate the association between pretransplant overall frailty and individual frailty components, with posttransplant outcomes among SPK and SPT recipients. Outcomes of interest were length of stay, kidney delayed graft function (K-DGF), readmission within 30 d after discharge, cardiovascular events, acute rejection, pancreas death-censored graft failure (DCGF), kidney DCGF, and death.

Results

Of the individual frailty components among SPK (n = 113), only slow walk time was associated with an increased risk of mortality (adjusted odds ratio [aOR]: 4.99; P = 0.03). Among SPT (n = 49), higher sum frailty scores (coefficient correlation 0.29; P = 0.04) and weight loss (coefficient correlation  = 0.30; P = 0.03) were associated with prolonged length of stay. Similarly, weight loss among SPT was associated with an increased risk of DCGF (aOR: 4.34; P = 0.049). Low grip strength was strongly associated with an increased risk of early readmission (aOR: 13.08; P = 0.008).

Conclusions

We found that not all components of frailty contribute equally to predicting outcomes. Objective measurements of slow walk time, unintentional weight loss, and low grip strength were found to be associated with less optimal outcomes in pancreas transplant recipients. Targeted interventions may improve posttransplant outcomes.

Chronic Pancreas Allograft Rejection Followed by Successful HLA-Incompatible Islet Alloautotransplantation: A Novel Strategy?

The purpose of pancreas or islet transplantation is to restore glycemic control in order to mitigate diabetes-related complications and prevent severe hypoglycemia. Complications from chronic pancreas allograft rejection may lead to transplantectomy, even when the endocrine function remains preserved. We present first evidence of a successful HLA incompatible islet re-transplantation with islets isolated from a rejecting pancreas allograft after simultaneous kidney pancreas transplantation. The pancreas allograft was removed because of progressively painful pancreatic panniculitis from clinically uncontrolled chronic rejection. The endocrine function was preserved. Induction treatment for this "islet alloautotransplantation" consisted of plasmapheresis, IVIg and alemtuzumab. At 1 year, the patient retained islet graft function with good glycemic control and absence of severe hypoglycemia, despite persistent low-grade HLA donor-specific antibodies. His panniculitis had resolved completely. In our point of view, islet alloautotransplantation derived from a chronically rejecting pancreas allograft is a potential option to salvage (partial) islet function, despite preformed donor-specific antibodies, in order to maintain stable glycemic control. Thereby it protects against severe hypoglycemia, and it potentially mitigates kidney graft dysfunction and other diabetes-related complications in patients with continued need for immunosuppression and who are otherwise difficult to retransplant.

Pancreas transplantation with grafts obtained from donation after cardiac death or donation after brain death results in comparable outcomes

Introduction

Pancreas organ shortages and long recipient waitlist times are critical components that limit recipients from receiving a pancreas transplant. Over the last decade, our center has been using donation after cardiac death (DCD) donors as an adjunct to donation after brain death (DBD) donors to expand the organ pool. The aim of this study was to compare recipient and graft survival between DCD and DBD recipients.

Methods

A retrospective single center propensity matched analysis (2011-2020) of 32 DCD vs 96 DBD pancreas transplants was performed.

Results

8-year recipient survival was similar between DCD and DBD groups (87.4% vs 92.7%, p=0.35) as was simultaneous kidney and pancreas transplant (SPK) 8-year kidney (88.9 vs 96.9%, p=0.219) and pancreas graft survival (77.4% vs 86.7%, p=0.344). There was no difference in vascular thrombosis rate between DCD and DBD pancreas grafts (3.1% vs 7.3%, p=0.73). DCD kidneys had a higher rate of DGF vs DBD kidneys (28.1% vs 6.3%, p=0.004), without any significant difference in long term kidney failure (12.5% vs 8.3%, p=0.5).

Discussion

Recipients of DCD grafts demonstrate equivalent long-term patient and graft survival compared to DBD recipients for pancreas transplantation. Increased utilization of well selected DCD donors is a safe strategy to increase the donor pool.

Comparison of long-term outcomes in simultaneous pancreas-kidney transplant versus simultaneous deceased donor pancreas and living donor kidney transplant

Simultaneous deceased donor pancreas and living donor kidney transplant (SPLK) has certain advantages over conventional simultaneous pancreas-kidney transplant (SPK) and may be beneficial for overcoming the paucity of organs needed for diabetic patients requiring transplant. We compared the clinical outcomes of patients who underwent either SPK (n = 149) or SPLK (n = 46) in terms of pre- and post-transplantation variables, development of de novo DSA, occurrence of biopsy-proven acute rejection (BPAR), and graft survival rates. There were no significant differences in the baseline characteristics between the SPK and SPLK groups except for the shorter cold ischemic time of kidney grafts, shorter duration of diabetes, older age of pancreas graft-donors, and younger age of kidney graft-donors in the SPLK group. Our results showed that the death-censored pancreas graft survival rate was lower in the SPLK group. In addition, the incidence of BPAR of the pancreas graft was higher in the SPLK group. There was no significant difference in the presence of de novo DSA and the rates of kidney graft failure, kidney BPAR, and mortality. Our results show that SPLK can be considered an alternative option for SPK although higher incidences of BPAR and graft failure of pancreas after SPLK need to be overcome.

Endoscopic visualization of graft status in patients with pancreas transplantation

BACKGROUND

Enteric drainage into the recipient duodenum in pancreas transplantation (PT) can identify the graft duodenum by endoscopy. This study aimed to identify the characteristic endoscopic findings associated with graft failure or acute rejection in patients with PT.

METHODS

We reviewed the medical records of patients who underwent PT with duodenoduodenostomy (DD) between January 2015 and August 2019. During this period, there were 44 PTs with DD in 42 patients; 122 endoscopies were performed and analyzed.

RESULTS

Overall, pancreatic graft survival was 82% at a mean follow-up of 27 months (range 6-55 months). There were 8 graft failures and 10 acute rejections. In all 8 graft failures, a deep ulcer covered with fibrinous exudates of the graft duodenum was confirmed on endoscopy. Diffuse erythema inside the graft duodenum was observed in 8 of 10 acute rejections. The factors associated with acute rejection were elevated serum lipase level (OR 8.5, p = 0.02) and diffuse erythema inside the graft duodenum on endoscopy (OR 20.5, p < 0.01) in multivariate analysis.

CONCLUSIONS

In PT with DD patients, graft failure can be visualized by endoscopy, and diffuse erythema inside the graft duodenum may be a finding of acute rejection.

The Presence of Donor-specific Antibodies Around the Time of Pancreas Graft Biopsy With Rejection Is Associated With an Increased Risk of Graft Failure

BACKGROUND

Donor-specific antibodies (DSA) against HLA are an important biomarker predicting graft injury, rejection (Rej), and failure in various solid-organ transplant recipients. However, the impact of DSA with or without histopathological evidence of rejection among pancreas transplant recipients (PTRs) is unknown.

METHODS

In this study, we included all PTRs at our center between 2005 and 2020, with pancreas allograft biopsy before March 31, 2021, and with DSA checked within 15 d of the biopsy. PTRs were divided into 4 groups based on the biopsy findings on the index biopsy and DSA status as Rej-/DSA-, Rej+/DSA-, Rej-/DSA+, and Rej+/DSA+.

RESULTS

Two hundred two PTRs had a pancreas allograft biopsy during the study period. Thirty-nine were in Rej-/DSA-, 84 Rej+/DSA-, 24 Rej-/DSA+, and 55 Rej+/DSA+. The mean interval from transplant to index biopsy was not statistically different between the 4 groups. The most common type of rejection was T cell-mediated rejection; however, antibody-mediated rejection was more prevalent in the Rej+/DSA+ group. At 5 y postbiopsy, the rate of death-censored graft failure (DCGF) for Rej-/DSA- was 18%, 24% in Rej+/DSA-; 17% in Rej-/DSA+ and 36% in Rej+/DSA+ (P = 0.14). In univariate analysis, mixed rejection (hazard ratio [HR], 3.0; 95% confidence intervals [CI], 1.22-7.39; P = 0.02) along with solitary pancreas transplantation and Rej+/DSA+ were associated with DCGF. In multivariate analysis, compared with Rej-/DSA-, Rej+/DSA+ was significantly associated with DCGF (HR, 2.32; 95% CI, 1.03-5.20; P = 0.04); however, Rej+/DSA- was not (HR, 1.06; 95% CI, 0.32-3.56; P = 0.92).

CONCLUSIONS

PTRs with pancreas allograft rejection and concomitant DSA have an increased risk of DCGF.

The Presence of Activated T Cell Subsets prior to Transplantation Is Associated with Increased Rejection Risk in Pancreas Transplant Recipients

Pancreas and islet transplantation (PTx) are currently the only curative treatment options for type 1 diabetes. CD4⁺ and CD8⁺ T cells play a pivotal role in graft function, rejection, and survival. However, characterization of immune cell status from patients with and without rejection of the pancreas graft is lacking. We performed multiparameter immune phenotyping of T cells from PTx patients prior to and 1 y post-PTx in nonrejectors and histologically confirmed rejectors. Our results suggest that rejection is associated with presence of elevated levels of activated CD4⁺ and CD8⁺ T cells with a gut-homing phenotype both prior to and 1 y post-PTx. The CD4⁺ and CD8⁺ T cells were highly differentiated, with elevated levels of type 1 inflammatory markers (T-bet and INF-γ) and cytotoxic components (granzyme B and perforin). Furthermore, we observed increased levels of activated FOXP3⁺ regulatory T cells in rejectors, which was associated with a hyporesponsive phenotype of activated effector T cells. Finally, activated T and B cell status was correlated in PTx patients, indicating a potential interplay between these cell types. In vitro treatment of healthy CD4⁺ and CD8⁺ T cells with tacrolimus abrogated the proliferation and cytokine (INF-γ, IL-2, and TNF-α) secretion associated with the type 1 inflammatory phenotype observed in pre- and post-PTx rejectors. Together, our results suggest the presence of activated CD4⁺ and CD8⁺ T cells prior to PTx confer increased risk for rejection. These findings may be used to identify patients that may benefit from more intense immunosuppressive treatment that should be monitored more closely after transplantation.

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.

[Pancreas transplantation-clinic, technique, and histological assessment]

BACKGROUND

In Germany pancreas transplants are performed in only a few selected and specialized centres, usually combined with a kidney transplant. Knowlegde of the indications for and techniques of transplantation as well as of the histopathological assessment for rejection in pancreas and duodenal biopsies is not very widespread.

AIM

To give an overview of the development and status quo in pancreas-kidney-transplantation in Germany summarizing the experience of the largest German pancreas transplant centre and to give a résumé of the results of histological diagnoses of biopsy specimens submitted between 06/2017 and 12/2020. Moreover, a detailed description and illustration of histological findings is included.

MATERIAL AND METHODS

A thorough literature search for aspects of the history, technique and indication for pancreas transplantation was performed and discussed in the context of the local experience and technical particularities specific for the transplant centre in Bochum. The occurrence of complications was compared with international reports. Results of pancreas and duodenal biopsies submitted to Erlangen between 06/2017 and 12/2020 for histological evaluation, which were evaluated according to the Banff classification, were summarized. For a better understanding key histological findings of pancreas rejection and differential diagnoses were illustrated and discussed.

RESULTS

A total of 93 pancreas transplant specimens and 3 duodenal biopsies were included. 34.4% of pancreas specimens did not contain representative material for a diagnosis. In the remaining 61 biopsies 24.6% showed no rejection, 62.3% were diagnosed with acute T-cell mediated rejection (TCMR) and 8.2% with signs suspicious of antibody-mediated rejection (ABMR). Acute acinary epithelial injury was seen in 59%, pancreatitis in 8.2% and allograft fibrosis was reported in as many as 54.1%. Calcineurin-inhibitor toxicity was discussed in only 4.9%.

CONCLUSION

Pancreas-kidney-transplantation and standardized histological assessment of the transplanted pancreas or rarely duodenum with reporting according to the updated Banff classification of pancreas transplants or previous reports of duodenal rejection are important mainstays in the management of patients with diabetes.

Immunological Monitoring in Beta Cell Replacement: Towards a Pathophysiology-Guided Implementation of Biomarkers

PURPOSE OF REVIEW

Grafted beta cells are lost because of recurrence of T1D and/or allograft rejection, two conditions diagnosed with pancreas graft biopsy, which is invasive and impossible in case of islet transplantation. This review synthetizes the current pathophysiological knowledge and discusses the interest of available immune biomarkers.

RECENT FINDINGS

Despite the central role of auto-(recurrence of T1D) and allo-(T-cell mediated rejection) immune cellular responses, the latter are not directly monitored in routine. In striking contrast, there have been undisputable progresses in monitoring of auto and alloantibodies. Except for pancreas recipients in whom anti-donor HLA antibodies can be directly responsible for antibody-mediated rejection, autoantibodies (and alloantibodies in islet recipients) have no direct pathogenic effect. However, their fluctuation offers a surrogate marker for the activation status of T cells (because antibody generation depends on T cells). This illustrates the necessity to understand the pathophysiology when interpreting a biomarker and selecting the appropriate treatment.

CT fluoroscopy-guided pancreas transplant biopsies: a retrospective evaluation of predictors of complications and success rates

To identify predictors of biopsy success and complications in CT-guided pancreas transplant (PTX) core biopsy. We retrospectively identified all CT fluoroscopy-guided PTX biopsies performed at our institution (2000-2017) and included 187 biopsies in 99 patients. Potential predictors related to patient characteristics (age, gender, body mass index (BMI), PTX age, PTX volume) and procedure characteristics (biopsy depth, needle size, access path, number of samples, interventionalist's experience) were correlated with biopsy success (sufficient tissue for histologic diagnosis) and the occurrence of complications. Biopsy success (72.2%) was more likely to be obtained in men [+25.3% (10.9, 39.7)] and when the intervention was performed by an experienced interventionalist [+27.2% (8.1, 46.2)]. Complications (5.9%) occurred more frequently in patients with higher PTX age [OR: 1.014 (1.002, 1.026)] and when many (3-4) tissue samples were obtained [+8.7% (-2.3, 19.7)]. Multivariable regression analysis confirmed male gender [OR: 3.741 (1.736, 8.059)] and high experience [OR: 2.923 (1.255, 6.808)] (biopsy success) as well as older PTX age [OR: 1.019 (1.002, 1.035)] and obtaining many samples [OR: 4.880 (1.240, 19.203)] (complications) as independent predictors. Our results suggest that CT-guided PTX biopsy should be performed by an experienced interventionalist to achieve higher success rates, and not more than two tissue samples should be obtained to reduce complications. Caution is in order in patients with older transplants because of higher complication rates.

Late complications of pancreas transplant

To summarize the long-term complications after pancreas transplantation that affect graft function, a literature search was carried out on the long-term complications of pancreatic transplantation, namely, complications from postoperative 3^rd mo onwards, in terms of loss of graft function, late infection and vascular complications as pseudoaneurysms. The most relevant reviews and studies were selected to obtain the current evidence on these topics. The definition of graft failure varies among different studies, so it is difficult to evaluate, a standardized definition is of utmost importance to know the magnitude of the problem in all worldwide series. Chronic rejection is the main cause of long-term graft failure, occurring in 10% of patients. From the 3rd mo of transplantation onwards, the main risk factor for late infections is immunosuppression, and patients have opportunistic infections like: Cytomegalovirus, hepatitis B and C viruses, Epstein-Barr virus and varicella-zoster virus; opportunistic bacteria, reactivation of latent infections as tuberculosis or fungal infections. Complete preoperative studies and serological tests should be made in all recipients to avoid these infections, adding perioperative prophylactic treatments when indicated. Pseudoaneurysm are uncommon, but one of the main causes of late bleeding, which can be fatal. The treatment should be performed with radiological endovascular approaches or open surgery in case of failure. Despite all therapeutic options for the complications mentioned above, transplantectomy is a necessary option in approximately 50% of relaparotomies, especially in life-threatening complications. Late complications in pancreatic transplantation threatens long-term graft function. An exhaustive follow-up as well as a correct immunosuppression protocol are necessary for prevention.

Early intestinal complications following pancreas transplantation: lessons learned from over 300 cases - a retrospective single-center study

Enteric complications remain a major cause of morbidity in the post-transplant period of pancreas transplantation despite improvements surgical technique. The aim of this single-center study was to analyze retrospectively the early intestinal complications and their potential relation with vascular events. From 2000 to 2016, 337 pancreas transplants were performed with systemic venous drainage. For exocrine secretion, intestinal drainage was done with hand-sewn anastomosis duodenojejunostomy. Twenty-three patients (6.8%) had early intestinal complications. Median age was 39 years (male: 65.2%). Median cold ischemia time was 11 h [IQR: 9-12.4]. Intestinal complications were intestinal obstruction (n = 7); paralytic ileus (n = 5); intestinal fistula without anastomotic dehiscence (n = 3); ischemic graft duodenum (n = 3); dehiscence of duodenojejunostomy (n = 4); and anastomotic dehiscence in jejunum after pancreas transplantectomy (n = 1). Eighteen cases required relaparotomy: adhesiolysis (n = 6); repeated laparotomy without findings (n = 1); transplantectomy (n = 6); primary leak closure (n = 3); re-positioning of the graft (n = 1); and intestinal resection (n = 1). Of the intestinal complications, 4 were associated with vascular thrombosis, resulting in two pancreatic graft losses. Enteric drainage with duodenum-jejunum anastomosis is safe and feasible, with a low rate of intra-abdominal complications. Vascular thrombosis associated with intestinal complications presents a risk factor for the viability of pancreatic grafts, so prevention and early detection is vital.

Pancreas transplants from small donors: are the outcomes acceptable? A retrospective study

Despite good organ quality, pancreata from extremely small pediatric donors (<30 kg) are generally avoided by many centers because of concerns of reduced islet cell mass and early technical failure. Therefore, we sought to compare the outcomes of small pancreas grafts (<30 kg) to those from higher weight donors from transplants performed between 1994 and 2015 (n = 1183). A total of 33 pancreata were from donors' ≤30 kg (3%), with a mean weight of 23.8 kg and mean age of 7.8 years. Patient survival was similar at 1, 5, and 10 years between recipients of ≤30 and >30 kg donors (≤30 kg: 96.8%, 86.8%, and 78.1% vs. >30 kg: 96.8%, 89.5%, and 79.1%, P = 0.5). Pancreas graft survival at 1, 5, and 10 years was also similar, ≤30 kg: 93.9%, 73.2%, and 61.0% vs. >30 kg: 87%, 73.3%, and 58.3% (P = 0.7). This graft survival pattern was also seen when comparing pancreata from ≤20 kg donors to those from >20 to 30 kg. Cause of graft loss, and metabolic and physiologic outcomes did not differ between the groups. After assessing the impact of donor weight as a continuous variable and calculating recipient-to-donor weight ratio (RDWR), we observed no effect of donor weight on patient and graft outcomes.

Alloimmunity in pancreas transplantation

PURPOSE OF REVIEW

Despite significant improvement in pancreas allograft survival, rejection continues to be a major clinical problem. This review will focus on emerging literature related to the impact of pretransplant and de-novo DSA (dnDSA) in pancreas transplant recipients, and the diagnosis and treatment of T-cell-medicated rejection (TCMR) and antibody-mediated rejection (ABMR) in this complex group of patients.

RECENT FINDINGS

Recent data suggest that pretransplant DSA and the emergence of dnDSA in pancreas transplant recipients are both associated with increased risk of ABMR. The pancreas allograft biopsy is essential for the specific diagnosis of TCMR and/or ABMR, distinguish rejection from other causes of graft dysfunction, and to guide-targeted therapy. This distinction is important especially in the setting of solitary pancreas transplants but also in simultaneous pancreas-kidney transplants where solid evidence has now emerged demonstrating discordant biopsy findings. Treatment of rejection in a functioning pancreas can prolong allograft survival.

SUMMARY

The accurate and timely diagnosis of active alloimmune destruction in pancreas transplant recipients is paramount to preserving graft function in the long term. This review will discuss new, rapidly evolving information that is valuable for the physician caring for these patients to achieve optimal immunological outcomes.

How Should Pancreas Transplant Rejection Be Treated?

BACKGROUND

Limited published data exist to guide the treatment of pancreas transplant rejection.

METHODS

We reviewed the treatment and outcomes of 158 first episodes of biopsy-proven pancreas rejection between 1 January 1997 and 31 December 2016. Within each Banff grade of rejection, we compared response rates and long-term outcomes with steroids alone versus steroids plus antithymocyte globulin (ATG).

RESULTS

Of 158 pancreas recipients with rejection, 65 were treated with steroids alone. Eighty-three percent of patients with grade I, 60% with grade II, and 33.33% with grade III rejection responded to treatment with steroids alone. Ninety-three patients were treated with steroids plus ATG. The response rates were 69% in grade I, 76% in grade II, and 73% in grade III. Response rates and graft survival were not different with grade I rejection treated with steroids alone versus steroids plus ATG. However, response rates and graft survival were significantly better with grade III rejection treated with the addition of ATG, and graft survival rates were significantly better with grade II rejection treated with the addition of ATG.

CONCLUSIONS

Grade I pancreas rejection can usually be successfully treated with steroids alone, whereas grade II and III rejection should usually be treated with steroids plus ATG, as the addition of ATG improves both response rates and graft survival.

Enteric Conversion of Bladder-drained Pancreas as a Predictor of Outcomes in Almost 600 Recipients at a Single Center

Complications associated with bladder-drained pancreata necessitating enteric conversion are common. Data on the outcomes after enteric conversion are conflicting. We studied the association between enteric conversion and the pancreas graft rejection, loss, and mortality.

Methods

At our center, 1117 pancreas transplants were performed between 2000 and 2016. We analyzed 593 recipients with bladder-drained pancreata, of which 523 received solitary transplants and 70 received simultaneous pancreas-kidney transplants. Kaplan-Meier function was used to estimate time to conversion by transplant type. Cox proportional hazards models were utilized to evaluate patient survival, death-censored graft survival, and acute rejection-free survival while treating conversion as a time-dependent covariate. Subsequently, we examined the association between timing of conversion and the same outcomes in the conversion cohort.

Results

At 10 y posttransplant, 48.8% of the solitary pancreas recipients and 44.3% of simultaneous pancreas-kidney transplant recipients had undergone enteric conversion. The enteric conversion was associated with 85% increased risk of acute rejection (hazard ratio [HR] = 1.85; 95% confidence interval [CI] = 1.37-2.49; P < 0.001). However, the conversion was not associated with graft loss or mortality. In the conversion cohort, a longer interval from engraftment to conversion was associated with an 18% lower rejection rate (HR = 0.82; 95% CI = 0.708-0.960; P = 0.013) and a 22% better graft survival (HR = 0.78; 95% CI = 0.646-0.946; P = 0.01).

Conclusions

Enteric conversion was associated with increased risk of rejection, but not increased risks of graft loss or mortality. The decision to convert should consider the increased rejection risk. A longer interval from engraftment to conversion appears favorable.

Sirolimus vs mycophenolate mofetil (MMF) in primary combined pancreas and kidney transplantation. Results of a long-term prospective randomized study

The study was intended to compare pancreas graft survival rates in two groups of pancreas and kidney transplant recipients prospectively randomized to treatment either with sirolimus or MMF. From 2002 to 2013, 238 type 1 diabetic recipients with end-stage kidney disease were randomized 1:1 to sirolimus or MMF treatment. Noncensored pancreas survival at 5 years was 76.4 and 71.6% for sirolimus and MMF groups, respectively (P > .05). Death-censored pancreas survival was better in the sirolimus group (P = .037). After removal of early graft losses pancreas survival did not differ between groups (MMF 83.1% vs sirolimus 91.6%, P = .11). Nonsignificantly more grafts were lost due to rejection in the MMF group (10 vs 5; P = .19). Cumulative patient 5-year survival was 96% in the MMF group and 91% in the sirolimus group (P > .05). Five-year cumulative noncensored kidney graft survival rates did not statistically differ (85.6% in the sirolimus group and 88.8% in MMF group). Recipients treated with MMF had significantly more episodes of gastrointestinal bleeding (7 vs 0, P = .007). More recipients in the sirolimus group required corrective surgery due to incisional hernias (21 vs 12, P = .019). ClinicalTrials No.: NCT03582878.

Inverse Association Between the Quantity of Human Peripheral Blood CXCR5+IFN-γ+CD8+ T Cells With De Novo DSA Production in the First Year After Kidney Transplant

BACKGROUND

We recently reported that a novel CXCR5IFN-γCD8 T-cell subset significantly inhibits posttransplant alloantibody production in a murine transplant model. These findings prompted the current study to investigate the association of human CD8 T cells with the same phenotype with the development of de novo donor-specific antibody (DSA) after kidney transplantation.

METHODS

In the current studies, we prospectively and serially analyzed peripheral blood CD8 and CD4 T-cell subsets and monitored for the development of de novo DSA in kidney transplant recipients during the first-year posttransplant. We report results on 95 first-time human kidney transplant recipients with 1-year follow-up.

RESULTS

Twenty-three recipients (24.2%) developed de novo DSA within 1-year posttransplant. Recipients who developed DSA had significantly lower quantities of peripheral CXCR5IFN-γCD8 T cells (P = 0.01) and significantly lower ratios of CXCR5IFN-γCD8 T cell to combined CD4 Th1/Th2 cell subsets (IFN-γCD4 and IL-4CD4 cells; P = 0.0001) compared to recipients who remained DSA-negative over the first-year posttransplant.

CONCLUSIONS

Our data raise the possibility that human CXCR5IFN-γCD8 T cells are a homolog to murine CXCR5IFN-γCD8 T cells (termed antibody-suppressor CD8 T cells) and that the quantity of CXCR5IFN-γCD8 T cells (or the ratio of CXCR5IFN-γCD8 T cells to Th1/Th2 CD4 T cells) may identify recipients at risk for development of DSA.

Eosinophil-to-monocyte ratio is an excellent predictor of acute cellular rejection in pancreas transplant alone recipients

Serum pancreatic enzymes (serum amylase and lipase) are sensitive markers for monitoring acute rejection in pancreatic transplant recipients. However, those enzymes are not specific, as their levels are elevated in other conditions. We evaluated the eosinophil-to-monocyte ratio (EMR) in peripheral blood as a biomarker of acute rejection in the clinical setting in recipients of pancreatic transplant alone. We performed 32 cases of pancreatic transplantation alone since 2015. Nine patients were diagnosed with rejection. Serum amylase and lipase levels and eosinophil and monocytes counts were analyzed and compared retrospectively between the non-rejection and rejection groups. The serum eosinophil count, eosinophil fraction of the complete blood count, and serum amylase and lipase levels were significant predictors of rejection according to the receiver operation characteristic (ROC) curve. However, the EMR was the best indicator of rejection based on the ROC curve (area under the curve 0.918, sensitivity 100%, specificity 76.2% at the cutoff value 0.80, P < .001). The combination of EMR and the lipase level had 100% sensitivity and 90.5% specificity. The EMR is a simple and excellent predictor of acute rejection in recipients of pancreatic transplant alone.

Pancreas allograft biopsies procedure in the management of pancreas transplant recipients

Pancreas transplantation is an effective therapy for diabetic patients, which can significantly improve the survival rate and quality of life of diabetic patients. According to the international registration of pancreas transplantation center, the global total pancreas transplantation has reached more than 80,000 cases by 2017, including pure pancreas transplantation and simultaneous pancreas-kidney transplantation (SPK). With the development and application of a new type of immunosuppressant, with the gradual maturity of organ preservation technology and surgical technology, the pancreas transplantation has rapidly on a global scale. However, pancreas transplantation still has more problems than limit its development compared with other organ transplantation. For example, the early diagnosis and treatment of pancreatic rejection are of considerable significance to the prognosis of pancreas transplantation. Some surveillance methods of diagnosis have been used increasingly, among which the histopathological diagnosis is particularly important. The first Banff schema for the histological diagnosis of pancreas rejection has been published, which primarily dealt with the diagnosis of acute T-cell-mediated rejection (ACMR). In recent years, antibody-mediated rejection (AMR) has been more emphasized as the primary cause of graft failure. The Banff pancreas allograft rejection grading schema was updated in 2011 by a broad-based multidisciplinary panel, presenting comprehensive guidelines for the diagnosis of AMR.

Transplant research in nonhuman primates to evaluate clinically relevant immune strategies in organ transplantation

Research in transplant immunology using non-human primate (NHP) species to evaluate immunologic strategies to prevent rejection and prolong allograft survival has yielded results that have translated successfully into human organ transplant patient management. Other therapies have not proceeded to human translation due to failure in NHP testing, arguably sparing humans the futility and risk of such testing. The NHP transplant models are ethically necessary for drug development in this field and provide the closest analogue to human transplant patients available. The refinement of this resource with respect to colony MHC typing, reagent and assay development, and availability to the research community has greatly enhanced knowledge about transplant immunology and drug development.

Genetic Polymorphism of HLA-G 14-bp Insertion/Deletion in Pancreas Transplant Recipients and Its Association With Type 1 Diabetes Mellitus

OBJECTIVES

Human leukocyte antigen-G is an immuno-modulatory factor that affects acute allograft rejection and autoimmune diseases such as type 1 diabetes mellitus. In this study, possible associations between human leukocyte antigen-G 14-bp insertion/deletion polymorphism and acute pancreas rejection were investigated.

MATERIALS AND METHODS

Human leukocyte antigen-G genotyping was assessed in 102 Iranian pancreas transplant recipients (including 41 with acute rejection and 61 with nonacute rejection). Results were compared with 100 individuals in a normal control group.

RESULTS

No significant differences in genotype frequencies of human leukocyte antigen-G 14-bp insertion / deletion were observed in recipients who had acute rejection episodes. On the other hand, the insertion / insertion genotype was a risk factor for susceptibility to type 1 diabetes mellitus (odds ratio = 3.82, 95% confidence interval, 1.37- 11.22; P = .005).

CONCLUSIONS

Our results provided evidence revealing that the human leukocyte antigen-G insertion / insertion genotype might be involved in the pathogenesis of type 1 diabetes mellitus.

Graft dysfunction in simultaneous pancreas kidney transplantation (SPK): Results of concurrent kidney and pancreas allograft biopsies

Simultaneous pancreas and kidney transplants offer significant therapeutic advantages but present a diagnostic approach dilemma in the diagnosis of rejection. Because both organs are from the same donor, the kidney has been treated traditionally as the "sentinel" organ to biopsy, presumably representing the status of both allografts. Truly concurrent biopsy studies, however, are needed to confirm this hypothesis. We examined 101 concurrent biopsies from 70 patients with dysfunction in either or both organs. Results showed concurrent rejection in 23 of 57 (40%) of cases with rejection; 19 of 57 (33.5%) and 15 of 57 (26.5%) showed kidney or pancreas only rejection, respectively. The degree and type of rejection differed in the majority (13 of 23, 56.5%) of cases with concurrent rejection, with the pancreas more often showing higher rejection grade. Taking into account pancreas dysfunction, a positive kidney biopsy should correctly predict pancreas rejection in 86% of the instances. However, the lack of complete concordance between the 2 organs, the discrepancies in grade and type of rejection, and the tendency for higher rejection grades in concurrent or pancreas only rejections, all support the rationale for pancreas biopsies. The latter provide additional data on the overall status of the organ, as well as information on nonrejection-related pathologies.

Outcomes in Pancreas Transplantation With Exocrine Drainage Through a Duodenoduodenostomy Versus Duodenojejunostomy

Until recently, pancreas transplantation has mostly been performed with exocrine drainage via duodenojejunostomy (DJ). Since 2012, DJ was substituted with duodenoduodenostomy (DD) in our hospital, allowing endoscopic access for biopsies. This study assessed safety profiles with DD versus DJ procedures and clinical outcomes with the DD technique in pancreas transplantation. DD patients (n = 117; 62 simultaneous pancreas-kidney [SPK_DD ] and 55 pancreas transplantation alone [PTA_DD ] with median follow-up 2.2 years) were compared with DJ patients (n = 179; 167 SPK_DJ and 12 PTA_DJ ) transplanted in the period 1998-2012 (pre-DD era). Postoperative bleeding and pancreas graft vein thrombosis requiring relaparotomy occurred in 17% and 9% of DD patients versus 10% (p = 0.077) and 6% (p = 0.21) in DJ patients, respectively. Pancreas graft rejection rates were still higher in PTA_DD patients versus SPK_DD patients (p = 0.003). Hazard ratio (HR) for graft loss was 2.25 (95% CI 1.00, 5.05; p = 0.049) in PTA_DD versus SPK_DD recipients. In conclusion, compared with the DJ procedure, the DD procedure did not reduce postoperative surgical complications requiring relaparatomy or improve clinical outcomes after pancreas transplantation despite serial pancreatic biopsies for rejection surveillance. It remains to be seen whether better rejection monitoring in DD patients translates into improved long-term pancreas graft survival.

The Banff 2015 Kidney Meeting Report: Current Challenges in Rejection Classification and Prospects for Adopting Molecular Pathology

The XIII Banff meeting, held in conjunction the Canadian Society of Transplantation in Vancouver, Canada, reviewed the clinical impact of updates of C4d-negative antibody-mediated rejection (ABMR) from the 2013 meeting, reports from active Banff Working Groups, the relationships of donor-specific antibody tests (anti-HLA and non-HLA) with transplant histopathology, and questions of molecular transplant diagnostics. The use of transcriptome gene sets, their resultant diagnostic classifiers, or common key genes to supplement the diagnosis and classification of rejection requires further consensus agreement and validation in biopsies. Newly introduced concepts include the i-IFTA score, comprising inflammation within areas of fibrosis and atrophy and acceptance of transplant arteriolopathy within the descriptions of chronic active T cell-mediated rejection (TCMR) or chronic ABMR. The pattern of mixed TCMR and ABMR was increasingly recognized. This report also includes improved definitions of TCMR and ABMR in pancreas transplants with specification of vascular lesions and prospects for defining a vascularized composite allograft rejection classification. The goal of the Banff process is ongoing integration of advances in histologic, serologic, and molecular diagnostic techniques to produce a consensus-based reporting system that offers precise composite scores, accurate routine diagnostics, and applicability to next-generation clinical trials.

2016 Comprehensive Update of the Banff Working Group on Liver Allograft Pathology: Introduction of Antibody-Mediated Rejection

The Banff Working Group on Liver Allograft Pathology reviewed and discussed literature evidence regarding antibody-mediated liver allograft rejection at the 11th (Paris, France, June 5-10, 2011), 12th (Comandatuba, Brazil, August 19-23, 2013), and 13th (Vancouver, British Columbia, Canada, October 5-10, 2015) meetings of the Banff Conference on Allograft Pathology. Discussion continued online. The primary goal was to introduce guidelines and consensus criteria for the diagnosis of liver allograft antibody-mediated rejection and provide a comprehensive update of all Banff Schema recommendations. Included are new recommendations for complement component 4d tissue staining and interpretation, staging liver allograft fibrosis, and findings related to immunosuppression minimization. In an effort to create a single reference document, previous unchanged criteria are also included.

A Single-center Experience on the Value of Pancreas Graft Biopsies and HLA Antibody Monitoring After Simultaneous Pancreas-Kidney Transplantation

BACKGROUND

In simultaneous pancreas-kidney transplantation (SPKT), monitoring of the pancreas allograft is more complex than the kidney allograft due to difficulties in obtaining pancreas histology and weak clinical evidence supporting the role of donor-specific antibodies (DSA).

METHODS

We performed a single-center retrospective analysis of all 17 SPKT recipients who underwent a total of 22 pancreas allograft indication biopsies from October 2009 to September 2012. Fifteen patients had at least 2 DSA measurements: pretransplantation and at the time of biopsy.

RESULTS

All 7 patients (100%) with post-transplantation DSA-positivity (de novo: n = 6; persistent: n = 1) at biopsy had at least 1 rejection episode either of the pancreas (n = 4) or the kidney (n = 3), with 3 antibody-mediated rejections (AMR). In contrast, only 4 of 8 patients (50%) without post-transplantation DSA had evidence of rejection, with 1 AMR. Findings during pancreas allograft biopsy procedures led to a change of immunosuppressive therapy in 11 of 15 (73%) patients. Patient survival, graft survival, and function were not adversely affected by the presence of post-transplantation DSA. One major and 2 minor procedure-related complications occurred during the pancreas biopsies.

CONCLUSIONS

In this small retrospective analysis, pancreas allograft histology provided the most therapeutically relevant information, rather than the kidney histology or DSA monitoring.

Pancreas Transplantation in the Modern Era

The field of pancreas transplantation has evolved from an experimental procedure in the 1980s to become a routine transplant in the modern era. With short- and long-term outcomes continuing to improve and the significant mortality, quality-of-life, and end-organ disease benefits, pancreas transplantation should be offered to more patients. In this article, we review current indications, patient selection, surgical considerations, complications, and outcomes in the modern era of pancreas transplantation.

Practical Applications in Immunohistochemistry: Evaluation of Rejection and Infection in Organ Transplantation

CONTEXT

-Immunohistochemical analysis of tissue biopsy specimens is a crucial tool in diagnosis of both rejection and infection in patients with solid organ transplants. In the past 15 years, the concept of antibody-mediated rejection has been refined, and diagnostic criteria have been codified in renal, heart, pancreas, and lung allografts (with studies ongoing in liver, small intestine, and composite grafts), all of which include immunoanalysis for the complement split product C4d.

OBJECTIVES

-To review the general concepts of C4d biology and immunoanalysis, followed by organ-allograft-specific data, and interpretative nuances for kidney, pancreas, and heart, with discussion of early literature for lung and liver biopsies. Additionally, practical applications and limitations of immunostains for infectious organisms (Polyomavirus, Adenoviridae [adenovirus], and the herpes virus family, including Herpes simplex virus, Cytomegalovirus, Human herpes virus 8, and Epstein-Barr virus) are reviewed in the context of transplant recipients.

DATA SOURCES

-Our experience and published primary and review literature.

CONCLUSIONS

-Immunohistochemistry continues to have an important role in transplant pathology, most notably C4d staining in assessment of antibody-mediated rejection and assessment of viral pathogens in tissue. In all facets of transplant pathology, correlation of morphology with special studies and clinical data is critical, as is close communication with the transplant team.

Diagnosis and Treatment of Pancreas Rejection

Despite significant improvement in pancreas allograft survival, rejection of the pancreas remains a major clinical problem. In addition to cellular rejection of the pancreas, antibody-mediated rejection of the pancreas is now a well-described entity. The 2011 Banff update established comprehensive guidelines for the diagnosis of acute and chronic AMR. The pancreas biopsy is critical in order to accurately diagnose and treat pancreas rejection. Other modes of monitoring pancreas rejection we feel are neither sensitive nor specific enough. In this review, we examine recent advances in the diagnosis and treatment of pancreas rejection as well as describe practical diagnostic and treatment algorithms.