Pancreas Allograft Biopsies Research Articles

Indications, Techniques, and Barriers for Pancreas Transplant Biopsy: A Consensus Perspective From a Survey of US Centers.

Pancreas transplant biopsy practices for the diagnosis of rejection or other pathologies are not well described. We conducted a survey of staff at US pancreas transplant programs (March 22, 2022, to August 22, 2022) to assess current program practices and perceptions about the utility and challenges in the performance and interpretation of pancreas allograft biopsies. Respondents represented 65% (76/117) of active adult pancreas transplant programs, capturing 66% of recent pancreas transplant volume in the United States. Participants were most often nephrologists (52%), followed by surgeons (46%), and other staff (4%). Pancreas allograft biopsies were performed mostly by interventional radiologists (74%), followed by surgeons (11%), nephrologists (8%), and gastroenterologists (1%). Limitations in the radiologist's or biopsy performer's comfort level or expertise to safely perform a biopsy, or to obtain sufficient/adequate samples were the two most common challenges with pancreas transplant biopsies. Pancreas transplant biopsies were read by local pathologists at a majority (86%) of centers. Challenges reported with pancreas biopsy interpretation included poor reliability, lack of reporting of C4d staining, lack of reporting of rejection grading, and inconclusive interpretation of the biopsy. Staff at a third of responding programs (34%) stated that they rarely or never perform pancreas allograft biopsies and treat presumed rejection empirically. This national survey identified significant variation in clinical practices related to pancreas allograft biopsies and potential barriers to pancreas transplant utilization across the United States. Consideration of strategies to improve program experience with percutaneous pancreas biopsy and to support optimal management of pancreas allograft rejection informed by histology is warranted.

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.

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

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

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

Introduction: Donor-specific antibodies (DSA) against human leukocyte antigen (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 Rej among pancreas transplant recipients (PTRs) is unknown. Method: In this study, we included all PTRs who had undergone either simultaneous pancreas-kidney or solitary pancreas transplant at our center between 2005 and 2020, with pancreas allograft biopsy before 03/2021, and with DSA checked within 15 days of the biopsy. Among PTRs with multiple biopsies during the study period, the first index biopsy was used to analyze the data. Pancreas biopsies at the time of implant or explant were excluded, as were biopsies with no pancreas tissue present. PTRs were divided into four groups based on the biopsy findings on the index biopsy and DSA status as Rej-/DSA-; Rej+/DSA-; Rej-/DSA+ and Rej+/DSA+. Results: A total of 352 pancreas allograft biopsies were performed in 203 PTRs during the study period. Of these, 203 PTRs, 41 were in Rej-/DSA-; 87 Rej+/DSA-; 24 Rej-/DSA+; and 51 Rej+/DSA+. Most of the baseline characteristics were similar between the groups, except PTRs in Rej-/DSA+ and Rej+/DSA+ were relatively younger, with a mean age of 39 compared to 43 for the other two groups. The mean interval from transplant to index biopsy was not statistically different between the four groups. The most common rejection was TCMR, however, AMR was more prevalent in the Rej+/DSA+ group. In addition, DSA against class II HLA was more prevalent in the DSA+/Rej + group. There was no statistical difference in the mean post index biopsy follow-up. At last follow up, the rate of death censored graft failure (DCGF) for Rej-/DSA- was 22%, 29% in Rej+/DSA-; 17% in Rej-/DSA+ and 39% in Rej+/DSA+. Although not statistically significant, there was a trend towards inferior pancreas graft survival in Rej+/DSA+ group by unadjusted K-M survival analysis (Figure 1).In multivariable analysis compared to Rej-/DSA-, Rej+/DSA+ was significantly associated with DCGF (HR: 2.25, 95% CI: 1.02 to 4.97; p=0.04), however Rej+/DSA- was not (HR: 1.40; 95% CI: 0.65 to 3.0; p=0.39). Conclusions: PTRs with pancreas allograft rejection in the presence of DSA have an increased risk of DCGF, and may warrant particularly aggressive management.

Molecular assessment of antibody-mediated rejection in human pancreas allograft biopsies.

Pancreas transplant longevity is limited by immune rejection, which is diagnosed by graft biopsy using the Banff Classification. The histological criteria for antibody-mediated rejection (AMR) are poorly reproducible and inconsistently associated with outcome. We hypothesized that a 34-gene set associated with antibody-mediated rejection in other solid organ transplants could improve diagnosis in pancreas grafts. The AMR 34-gene set, comprising endothelial, natural killer cell and inflammatory genes, was quantified using the NanoString platform in 52 formalin-fixed, paraffin-embedded pancreas transplant biopsies from 41 patients: 15 with pure AMR or mixed rejection, 22 with T cell-mediated rejection/borderline and 15 without rejection. The AMR 34-gene set was significantly increased in pure AMR and mixed rejection (P=.001) vs no rejection. The gene set predicted histological AMR with an area under the receiver operating characteristic curve (ROC AUC) of 0.714 (P=.004). The AMR 34-gene set was the only biopsy feature significantly predictive of allograft failure in univariate analysis (P=.048). Adding gene expression to DSA and histology increased ROC AUC for the prediction of failure from 0.736 to 0.770, but this difference did not meet statistical significance. In conclusion, assessment of transcripts has the potential to improve diagnosis and outcome prediction in pancreas graft biopsies.

Alloimmunity in pancreas transplantation.

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 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. 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.

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.

Tacrolimus-Induced BMP/SMAD Signaling Associates With Metabolic Stress-Activated FOXO1 to Trigger β-Cell Failure.

Active maintenance of β-cell identity through fine-tuned regulation of key transcription factors ensures β-cell function. Tacrolimus, a widely used immunosuppressant, accelerates onset of diabetes after organ transplantation, but underlying molecular mechanisms are unclear. Here we show that tacrolimus induces loss of human β-cell maturity and β-cell failure through activation of the BMP/SMAD signaling pathway when administered under mild metabolic stress conditions. Tacrolimus-induced phosphorylated SMAD1/5 acts in synergy with metabolic stress-activated FOXO1 through formation of a complex. This interaction is associated with reduced expression of the key β-cell transcription factor MAFA and abolished insulin secretion, both in vitro in primary human islets and in vivo in human islets transplanted into high-fat diet-fed mice. Pharmacological inhibition of BMP signaling protects human β-cells from tacrolimus-induced β-cell dysfunction in vitro. Furthermore, we confirm that BMP/SMAD signaling is activated in protocol pancreas allograft biopsies from recipients on tacrolimus. To conclude, we propose a novel mechanism underlying the diabetogenicity of tacrolimus in primary human β-cells. This insight could lead to new treatment strategies for new-onset diabetes and may have implications for other forms of diabetes.

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.

Laparoscopic Biopsies in Pancreas Transplantation.

As there is no precise laboratory test or imaging study for detection of pancreas allograft rejection, there is increasing interest in obtaining pancreas tissue for diagnosis. Pancreas allograft biopsies are most commonly performed percutaneously, transcystoscopically, or endoscopically, yet pancreas transplant surgeons often lack the skills to perform these types of biopsies. We have performed 160 laparoscopic pancreas biopsies in 95 patients. There were 146 simultaneous kidney-pancreas biopsies and 14 pancreas-only biopsies due to pancreas alone, kidney loss, or extraperitoneal kidney. Biopsies were performed for graft dysfunction (89) or per protocol (71). In 13 cases, an additional laparoscopic procedure was performed at the same operation. The pancreas diagnostic tissue yield was 91.2%; however, the pancreas could not be visualized in eight cases (5%) and in 6 cases the tissue sample was nondiagnostic (3.8%). The kidney tissue yield was 98.6%. There were four patients with intraoperative complications requiring laparotomy (2.5%) with two additional postoperative complications. Half of all these complications were kidney related. There were no episodes of pancreatic enzyme leak and there were no graft losses related to the procedure. We conclude that laparoscopic kidney and pancreas allograft biopsies can be safely performed with very high tissue yields.

Fever of Unkown Origin as a Sole Manifestation of Pancreas Allograft Rejection

Fever in a transplant recipient is almost always suspicious of an infectious etiology. We present a patient with simultaneous pancreas and kidney transplant who had persistent high grade fever for a month which could only be attributed to pancreas allograft rejection. A 56 year old white man with history of simultaneous kidney-pancreas transplant (SPK) a month prior presented with fever of unknown etiology. Patient denied any sick contacts or any localizing signs and symptoms. On examination, his temperature was 102.1 °F. Rest of the examination was unremarkable. His immunosuppression consisted of tacrolimus 3 mg twice daily, mycophenolate 1000 mg twice daily, and Prednisone 10 mg daily. Initial laboratory work up showed serum creatinine 1.8 mg/dl (Baseline serum Cr 1.8-2.0 mg/dl), tacrolimus level 14 ng/dl, serum amylase 82, serum lipase 67, glucose 89 mg/dl, and normal urine analysis. In addition, blood culture, urine culture, and serum cytomegalovirus, Epstein Barr virus and BK virus PCR were negative. Chest X ray and CT scan of abdomen and pelvis did not show any significant pathology. Patient's fever continued unabated in the range of 100-103°F daily for a month despite empirical antibiotic therapy while cultures remained negative. Rest of the negative work-up included an echocardiogram, kidney ultrasound with kidney biopsy, cerebrospinal fluid analysis, tagged white blood cell scan, upper and lower gastrointestinal scopes with biopsy of gastrointestinal mucosa for any viral inclusions. Nuclear PET scan showed increased activity in the pancreas transplant. Pancreas allograft biopsy confirmed pancreas allograft rejection although serum amylase and lipase were normal at the time of biopsy. Fever disappeared after initiation of steroids and has not recurred since discharge from the hospital 3 months ago. In conclusion, pancreas allograft rejection may present as fever of unknown etiology in a pancreas transplant recipient. Serum amylase and lipase may not be the reliable markers of pancreatic transplant rejection.

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

BackgroundIn 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). MethodsWe 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. ResultsAll 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. ConclusionsIn this small retrospective analysis, pancreas allograft histology provided the most therapeutically relevant information, rather than the kidney histology or DSA monitoring.

Acute Cellular and Antibody-Mediated Rejection of the Pancreas Allograft: Incidence, Risk Factors and Outcomes

Antibody-mediated rejection (AMR) after pancreas transplantation is a recently identified entity. We describe the incidence of, risk factors for, and outcomes after AMR, and the correlation of C4d immunostaining and donor-specific antibody (DSA) in the diagnosis of AMR. We retrospectively analyzed 162 pancreas transplants in 159 patients who underwent 94 pancreas allograft biopsies between 2006 and 2009. Univariate and multivariate analyses were performed to evaluate risk factors for pancreas graft AMR. One-year rejection rates and survival after rejection were calculated by Kaplan-Meier methods. AMR occurred in 10% of patients by 1-year posttransplant. Multivariate risk factors identified for AMR include nonprimary simultaneous pancreas-kidney (SPK) transplant, primary solitary pancreas (PAN) transplant and race mismatch. After pancreas rejection, patient survival was 100% but 20% (8 of 41) of pancreas grafts failed within 1 year. Graft survival after acute cellular rejection (ACR), AMR and mixed rejection was similar. Of biopsies that stained >5% C4d, 80% were associated with increased Class I DSA. In summary, AMR occurs at a measurable rate after pancreas transplantation, and the diagnosis should be actively sought using C4d staining and DSA levels in patients with graft dysfunction, especially after nonprimary SPK and primary PAN transplantation.

Distinctive morphological features of antibody-mediated and T-cell-mediated acute rejection in pancreas allograft biopsies

Two main histopathological types of acute rejection are recognized in solid organ transplantation: T-cell-mediated rejection (TCMR) and antibody-mediated rejection (AMR). In pancreas allografts the contrasting morphological features of these entities have only recently been described. Acute TCMR is characterized by active septal infiltrates composed predominantly of T cells and often involving veins (venulitis) and ducts (ductitis). Inflammation of the arterial endothelium (intimal arteritis or endarteritis) may be present. Focal or diffuse acinar inflammation (acinitis) is also typical of TCMR. Acute AMR in contrast, is characterized by predominantly macrophagic (± neutrophilic) inflammation, concentrated in, and around the interacinar microvasculature (interacinar inflammation, capillaritis) and typically shows focal or diffuse C4d staining of the interacinar capillaries. Architectural preservation is common in milder forms of AMR, whereas severe or untreated forms lead to extensive vascular injury and secondary parenchymal hemorrhagic necrosis. These morphological features strongly correlate with the presence of circulating donor-specific antibody (DSA)+. Stereotypical TCMR and AMR, as well as mixed forms of rejection can be confidently diagnosed in pancreas allograft biopsies with the combination of three elements: systematic analysis of the histological features; evaluation of C4d staining; and determination of the DSA status.

Eosinophilia as an early indicator of pancreatic allograft rejection

Monitoring pancreas transplant recipients for rejection is an inexact science. Serial monitoring of urinary amylase has been used for patients with a bladder-drained pancreas. An increase in serum amylase and lipase has been utilized as an in vivo measure of pancreas rejection in patients with enteric pancreatic exocrine drainage. Decreases in urinary amylase or increases in serum amylase or lipase, respectively, in these two different types of surgical drainage would prompt a pancreas biopsy for histologic confirmation of rejection. Herein, we describe the case of an enteric-drained pancreatic transplant recipient who presented with peripheral eosinophilia at least one month before she developed increases in serum amylase and lipase. A pancreas allograft biopsy indicated eosinophilic acute cellular rejection. Peripheral eosinophilia may be a useful early indicator of pancreas graft rejection preceding changes in serum pancreatic enzymes by approximately one month.

Pancreas Allograft Rejection: Analysis of Concurrent Renal Allograft Biopsies and Posttherapy Follow-Up Biopsies

Pancreas and kidney allograft function is routinely monitored with serum studies (amylase, lipase, and creatinine). Increased levels commonly prompt tissue biopsy, to diagnose cause of graft dysfunction. Historically, pancreas allografts were infrequently biopsied, although serum enzymes and renal rejection may be poor surrogates for pancreas status. Pancreas allograft biopsies at our center were reviewed and reclassified according to University of Maryland (UMD) and Banff criteria; C4d immunostaining was performed. Findings were correlated with clinical data and renal allograft biopsies. Fifty-six pancreas allograft biopsies from 27 patients were evaluated. UMD and Banff grading were similar, although two UMD "indeterminate" biopsies were Banff grade 1 rejection. There were 21 concurrent pancreas and renal biopsies, all from simultaneous pancreas-kidney allograft recipients. Thirteen pairs were concordant for rejection; eight pairs were discordant for rejection (38%); six pairs showed pancreas rejection without kidney rejection, and two pairs showed the converse. Fourteen patients had a total of 21 follow-up pancreas allograft biopsies. Seven biopsies showed a lower grade of rejection on follow-up biopsy, 4 biopsies showed more severe rejection, and 10 had unchanged grade. In only 9 of these 21 (43%) cases, did the interval serum amylase or lipase trend parallel the subsequent biopsy diagnosis. With a high biopsy discordance rate, our data suggest that renal allograft rejection is a poor surrogate for pancreas allograft status. Likewise, serum amylase and lipase levels do not predict response to rejection therapy. Surveillance or posttherapy pancreas allograft biopsies may be a useful means to monitor pancreas allograft status.

Pancreas Allograft Biopsies with Positive C4d Staining and Anti‐Donor Antibodies Related to Worse Outcome for Patients

C4d+ antibody-mediated rejection following pancreas transplantation has not been well characterized. Therefore, we assessed the outcomes of 27 pancreas transplantation patients (28 biopsies), with both C4d staining and donor-specific antibodies (DSA) determined, from a cohort of 257 patients. The median follow-up was 50 (interquartile range [IQR] 8-118) months. Patients were categorized into 3 groups: group 1, patients with minimal or no C4d staining and no DSA (n = 13); group 2, patients with either DSA present but no C4d, diffuse C4d+ and no DSA or focal C4d+ and DSA (n = 6); group 3, patients with diffuse C4d+ staining and DSA (n = 9). Active septal inflammation, acinar inflammation and acinar cell injury/necrosis were significantly more abundant in group 3 than in group 2 (respective p-values: 0.009; 0.033; 0.025) and in group 1 (respective p-values: 0.034; 0.009; 0.002). The overall uncensored pancreas graft survival rate for groups 1, 2 and 3 were 53.3%, 66.7% and 34.6%, respectively (p = 0.044). In conclusion, recipients of pancreas transplants with no C4d or DSA had excellent long-term graft survival in comparison with patients with both C4d+ and DSA present. Hence, C4d should be used as an additional marker in combination with DSA in the evaluation of pancreas transplant biopsies.

Histologic Studies of Islets of Langerhans in Transplanted Pancreata from Marginal Donors in Japan

The serious shortage of brain-dead donors leads to the use of pancreata from marginal donors, including cardiac death in Japan. We studied the islet histology of pancreas graft biopsies to investigate the adequacy of using pancreata from marginal donors. Pancreas allograft biopsy was performed originally to diagnose acute rejection (Drachenberg grade I–III) at a mean of 6 months after transplantation. The percentage of β cells showing oxidative DNA changes, replication, and apoptosis was investigated in 7 recipients of simultaneous pancreas-kidney transplantations with good graft function from marginal donors. Their causes of death were cerebrovascular with donor ages >44 years (n = 3), cardiac (n = 2), and cerebrovascular (n = 2). The percentage of β cells per islet in the transplanted pancreas (71.9 ± 3.3%) did not correlate with glycemic control or insulin secretion, but did correlated inversely with donor age (r = −0.81; P < .05). Oxidative DNA changes as revealed by 8-hydroxy-2′-deoxyguanosine (8-OHdG) staining were diffusely present in islet cells as well as in the exocrine cells of the transplanted pancreas. The percentage of 8-OHdG–positive cells per pancreas (71.8 ± 4.5%) did not correlate with glycemic levels, insulin secretion, donor age, or ischemic time. There were no Ki67-positive replicating cells or terminal deoxynucleotide transferase–mediated dUTP nick-end labeling–positive apoptotic islet cells. Transplanted pancreata from marginal donors showed preserved β cells and function despite diffuse oxidative changes.

Antibody-Mediated Rejection of the Pancreas Allograft

Antibody-mediated rejection (AMR) is an entity that is being increasingly recognized in the setting of solid organ transplantation. Clinical, pathologic, and serologic criteria are perhaps better defined and understood in kidney and heart transplants (1), but little is known for other solid organs, including lung, pancreas, liver, and small intestine transplantation. In an effort to understand the impact and significance of alloantibodies in the setting of pancreas transplantation, we systematically screen for donor-specific antibodies (DSA) and immunolabel with C4d all pancreas allograft biopsies at our institution. In a study of 136 recipients of simultaneous pancreas and kidney transplants, we initially reported two patients with histologic evidence of both kidney and pancreas acute AMR, with diffusely C4d-positive peritubular and interacinar capillary staining, respectively. Both patients had documented circulating DSA. One patient lost both kidney and pancreas allografts 1 year posttransplant, and the second patient fully recovered kidney and pancreas allografts with normal function 2 years posttransplant (2). More recently, in our study of 18 pancreas allograft recipients and 27 biopsies, we found a significant correlation between circulating DSA and C4d staining of interacinar capillaries, and no correlation of DSA with biopsy staining of larger arteries, veins, islets, or interstitium (3). In this study, half of the patients returned to insulin therapy and half of the patients retained normal allograft function after a mean follow-up period of 316.3 days. Patients with pure acute cellular rejection fully recovered allograft function after a mean follow-up period of 208.4 days. The decreased allograft survival in AMR+pancreas recipients is in agreement with the decreased survival shown in C4d+AMR patients reported by Munivenkatappa (4). We have also looked at the potential role of C3d, another proposed tissue marker of antibody activation and deposition in kidney transplant (5). In a group of 16 pancreas allografts, C3d proved to be less sensitive than C4d in identifying patients with AMR, and there was no correlation with class I or class II DSA (Poster presentation to the 2009 ATC). We agree with the viewpoints of Dr. Munivenkatappa, Dr. Papadimitriou, and Dr. Drachenberg in their letter to the editor of this edition of Transplantation. In pancreas transplantation (as in other solid organ transplant) there is perhaps a spectrum of clinical scenarios, tissue evidence of antibody activation, and serologic patterns that still need to be defined to better understand AMR as an entity in the pancreas allograft. The diagnostic criteria for AMR in the pancreas (6) will be a subject of important discussions in the next Banff meeting in Alberta, Canada, August 2009, and will undoubtedly undergo refinement in the future. Jose R. Torrealba Department of Pathology University of Wisconsin Madison, WI Jon Odorico Department of Surgery University of Wisconsin Madison, WI

Interacinar C4d Staining in Pancreas Allografts

We read with great interest the award winning article of Torrealba et al. (1) demonstrating the association between circulating donor-specific antibodies (DSA) and C4d+ interacinar staining in pancreas allograft biopsies (PcABx). This study is important because pancreatic antibody-mediated allograft rejection (AMR) has been under recognized and a systematic approach to its clinical and pathological diagnosis is needed. In kidney transplants, circulating DSA and biopsy C4d+ are essential for a histological diagnosis of acute AMR, provided the biopsy also shows morphologica evidence of acute tissue injury (capillary or glomerular inflammation, microthrombi, or acute tubular necrosis) (2). Furthermore, C4d+ in the absence of injury falls into a descriptive category short of AMR (2). On the basis of more limited evidence, guidelines were proposed to diagnose AMR in PcABx. This categorization also relies on a combination of elements (DSA+, C4d+, graft dysfunction; 3). Torrealba et al. provide strong support for the systematic use of C4d stains in PcATx. Their study identifies interacinar C4d+ as the most specific pattern of positivity with respect to AMR. In our view, it would be useful to emphasize that the “interacinar” pattern may be partially or completely lost when there is ongoing-chronic AMR (“active chronic AMR”) leading to extensive fibrosis. In those cases, C4d interacinar staining may remain in the atrophic exocrine remnants but it may be seen also in capillary walled vessels throughout the fibrotic parenchyma (4). Also, larger vessel (rather than interacinar staining) for complement (including C4d and immunoglobulin components) is seen in the wall of necrotic arteries and veins in the rare but cataclysmic cases of “accelerated AMR” typically presenting with graft thrombosis (3). Also, in our patient population, interacinar C4d+ identifies patients with significant amounts of circulating DSA and correlates with AMR (5), but we have been puzzled by the various clinical settings in which C4d+ is encountered. More specifically, over a period of 12 months (2007), only 2 of 4 SPK patients with unequivocal interacinar C4d+ had typical acute AMR (seen in both grafts). The third patient had progressive failure of both kidney and pancreas, and renal biopsies showed typical active chronic AMR. Interestingly, in the pancreas, C4d+ was associated with features of recurrent diabetes mellitus: preserved acinar and endocrine components but complete loss of beta cells with preservation of alpha cells. This case raises important questions about possible mechanisms of graft injury in AMR (i.e. islet-beta cell microvascular injury) and the possible interplay between allo- and autoimmu nity. Finally, in the fourth patient, PcATx done 3 months apart during the eighth year posttransplantation showed diffuse C4d+ (and circulating DSA) but the patient continues to be euglycemic after 12 additional months of follow-up (ninth year posttransplantation) without any treatment of AMR. Similar to the kidney, delineation of a set of morphological features of tissue injury in addition to C4d+ would be useful to further understand the pathophysiology of AMR. Concurrent cell-mediated rejection (seen in 18 of 27 cases in the study of Torrealba et al.) and nonspecific (secondary) tissue inflammation may be confounding factors of AMR. In cases with “pure” acute AMR (i.e. lacking T-cell infiltrates), including the two cases described earlier, we have typically found a disproportionate amount of acinar cell injury (Fig. 1). This ranges from scattered apoptotic bodies within the acini, to massive cytoplasmic vacuolization, swelling and cell drop-out that may be attributed to the microvascular injury associated with AMR. In the more severe cases, capillary dilatation (congestion) and interacinar “capillaritis” (mononuclear, neutrophilic, or mixed), as described by Torrealba et al., are also noted (Fig. 1).FIGURE 1.: Pancreas' biopsy in a patient with acute antibody-mediated allograft rejection 2 weeks posttransplantation. (A) Marked acinar cell injury including cytoplasmic swelling and vacuolization. There are scattered apoptotic cells and apoptotic nuclear fragments (arrows). The cell injury is disproportionate to the recognizable inflammatory infiltrates (CD3 stain showed rare T cells). There were no features of cell-mediated rejection. The interacinar capillaries are congested. (B) C4d stain outlines interacinar capillaries. (C) Macrophage stain (CD68) demonstrates that interacinar capillaries are engorged with macrophages in a manner similar to the “capillaritis” described in peritubular capillaries in renal acute antibody-mediated allograft rejection.Increased recognition of AMR in PcABx raises issues that overlap with those in other solid organ transplants, but also organ-specific which need to be addressed independently. Raghava B. Munivenkatappa Benjamin Philosophe John C. Papadimitriou Cinthia B. Drachenberg Division of Transplantation Departments of Surgery and Pathology Baltimore, MD