C4d-positive interacinar capillaries correlates with donor-specific antibody-mediated rejection in pancreas allografts

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.

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.

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

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.

Antibody-mediated rejection across solid organ transplants: manifestations, mechanisms, and therapies

Solid organ transplantation is a curative therapy for hundreds of thousands of patients with end-stage organ failure. However, long-term outcomes have not improved, and nearly half of transplant recipients will lose their allografts by 10 years after transplant. One of the major challenges facing clinical transplantation is antibody-mediated rejection (AMR) caused by anti-donor HLA antibodies. AMR is highly associated with graft loss, but unfortunately there are few efficacious therapies to prevent and reverse AMR. This Review describes the clinical and histological manifestations of AMR, and discusses the immunopathological mechanisms contributing to antibody-mediated allograft injury as well as current and emerging therapies.

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.

APT070 (mirococept), a membrane-localizing C3 convertase inhibitor, attenuates early human islet allograft damage in vitro and in vivo in a humanized mouse model

Background and Purpose

A major obstacle to islet cell transplantation is the early loss of transplanted islets resulting from the instant blood‐mediated inflammation reaction (IBMIR). The activation of complement pathways plays a central role in IBMIR. The aim of this study was to test the inhibitory effect of “painting” human islets with APT070, a membrane‐localizing C3 convertase inhibitor, on inflammation evoked by exposure to human serum in vitro and by transplantation in vivo in a humanized diabetic mouse model.

Experimental Approach

In vitro, human islets pre‐incubated with APT070 were exposed to allogeneic whole blood. In vivo, similarly treated islets were transplanted underneath the kidney capsule of streptozotocin‐induced diabetic NOD‐SCID IL2rγ^−/− mice that had been reconstituted with human CD34⁺ stem cells. Complement activation and islet hormone content were assayed using enzyme‐linked immunosorbent assays. Supernatants and sera were assayed for cytokines using cytometric beads array. Morphology of the islets incubated with human serum in vitro and in graft‐bearing kidney were evaluated using immunofluorescence staining.

Key Results

Pre‐incubation with APT070 decreased C‐peptide release and iC3b production in vitro, with diminished deposition of C4d and C5b‐9 in islets embedded in blood clots. In vivo, the APT070‐treated islets maintained intact structure and showed less infiltration of inflammatory cells than untreated islets. The pretreatments also significantly reduced pro‐inflammatory cytokines in supernatants and sera.

Conclusions and Implications

Pre‐treatment of islets with APT070 could reduce intra‐islet inflammation with accompanying preservation of insulin secretion by beta cells. APT070 could be as a potential therapeutic tool in islet transplantation.

Clinical significance of donor-specific human leukocyte antigen antibodies in liver transplantation

Antibody-mediated rejection (AMR) caused by donor-specific anti-human leukocyte antigen antibodies (DSA) is widely accepted to be a risk factor for decreased graft survival after kidney transplantation. This entity also plays a pathogenic role in other solid organ transplants as it appears to be an increasingly common cause of heart graft dysfunction and an emerging issue in lung transplantation. In contrast, the liver appears relatively resistant to DSA-mediated injury. This “immune-tolerance” liver property has been sustained by a low rate of liver graft loss in patients with preformed DSA and by the intrinsic liver characteristics that favor the absorption and elimination of DSA; however, alloantibody-mediated adverse consequences are increasingly being recognized, and several cases of acute AMR after ABO-compatible liver transplant (LT) have been reported. Furthermore, the availability of new solid-phase assays, allowing the detection of low titers of DSA and the refinement of objective diagnostic criteria for AMR in solid organ transplants and particularly in LT, have improved the recognition and management of this entity. A cost-effective strategy of DSA monitoring, avoidance of class II human leukocyte antigen mismatching, judicious immunosuppression attached to a higher level of clinical suspicion of AMR, particularly in cases unresponsive to conventional anti-rejection therapy, can allow a rational approach to this threat.

MHC class I signaling: new functional perspectives for an old molecule

Donor-specific antibodies are associated with refractory rejection episodes and poor allograft outcomes in solid organ transplantation. Our understanding of antibody-mediated allograft injury is expanding beyond complement deposition. In fact, unique mechanisms of alloantibodies are advancing our knowledge about transplant vasculopathy and antibody-mediated rejection. These include direct effects on the endothelium, resulting in the recruitment of leukocytes, chemokine and cytokine production, and stimulation of innate and adaptive alloresponses. These effects will be the focus of the following review.

Anti-donor HLA class I antibodies: pathways to endothelial cell activation and cell-mediated allograft rejection

BACKGROUND

The development of donor-specific human leukocyte antigen (HLA) class I antibodies after organ transplantation is associated with subsequent acute and chronic rejection. The aim of this study was to examine the role of anti-HLA class I antibody in modulating endothelium-leukocyte interaction.

METHODS

Human microvascular endothelial cells (HMEC-1) stimulated with HLA class I antibody (W6/32) or allospecific antibodies from sensitized patients (n=6) were examined for activation of transcription factor CREB by Western blotting. Up-regulation of endothelial adhesion molecules and chemokines was measured by flow cytometry and quantitative polymerase chain reaction, respectively. Leukocyte adhesion was evaluated by chemotaxis and in vitro flow-based assays.

RESULTS

Treatment of HMEC-1 cells with HLA class I antibody resulted in the phosphorylation of CREB in protein kinase A-dependent pathway. Furthermore, there was a significant increase in the expression of cell surface VCAM-1 (Akt-dependent) and ICAM-1 in Akt-dependent and extracellular signal-regulated kinase-dependent manner (P<0.001). Additionally, exposure to W6/32 antibody induced significant expression of interleukin-6, CXCL8, CXCL10, and CCL5. Knockdown of CREB produced a reduction in W6/32-induced CXCL8 expression (P<0.001). Media from W6/32-treated endothelial cells induced a significant monocyte chemotaxis (P<0.001) and flow-based adhesion assay demonstrated an increase in monocyte adhesion to endothelial cells compared with the control group (P<0.001). Importantly, allospecific antibodies from sensitized patients also activated endothelial CREB and significantly up-regulated VCAM-1, ICAM-1, and CXCL8.

CONCLUSION

These findings suggest that donor-specific HLA class I antibodies directly activate endothelial cells leading to an increase in their potential to recruit and bind recipient leukocytes, thereby increasing the potential for allograft inflammation.

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.

Pancreas transplantation, antibodies and rejection: where do we stand?

PURPOSE OF REVIEW

Antibody-mediated rejection (AMR) is acknowledged and defined in kidney transplantation, but where do we stand as far as pancreas transplantation is concerned? Here we appraise the most recent findings in pancreatic AMR and give suggestions for future research in the field by addressing currently unresolved issues.

RECENT FINDINGS

Five main topics are discussed: chronological assessment of all literature on biopsy-proven pancreatic AMR; role of C4d and recent development in other markers; the use of sentinel organs, such as kidney biopsies and duodenal patch biopsies for diagnosis of pancreatic AMR; studies addressing islet pathology and its relevance in AMR; and protocol and follow-up pancreas biopsy practice in relation to pancreas transplant management and survival.

SUMMARY

Antibody-mediated processes play a role in pancreas transplantation. However, sensitive markers, pathophysiological understanding, and adequate interventions have not yet been established. Much data are still lacking and we believe that studying protocol and follow-up biopsies along with serial donor-specific antibody data may improve pancreas transplant patient management and outcomes.

Graft dysfunction in pancreas and islet transplantation: morphological aspects

PURPOSE OF REVIEW

β-Cell replacement in the form of whole pancreas transplantation (WPnTx) or islet transplantation has the goal of providing long-term insulin independence to diabetic patients that may require these types of interventions, with the minimum of iatrogenic side-effects and complications. In search of these ambitious and only partially achieved objectives, continuous advances are made in the field.

RECENT FINDINGS

A concerted effort has been made in recent years to categorize the morphological features of allograft rejection in WPnTx. This has followed the general attempts to standardize histopathological and other diagnostic modalities in solid organ transplantation in general. Issues related to antibody-mediated rejection have taken center stage due to their perceived dramatic effects on both short and long-term graft survival. Another issue that diminishes the extent of success with WPnTx is the high incidence of posttransplant diabetes mellitus (PTDM). Understanding the mechanisms involved in this process is important for the development of potential therapeutic interventions and for its prevention.

SUMMARY

This review will summarize the current understanding on the morphological features of antibody-mediated rejection in WPnTx, the main morphological and clinical aspects of PTDM, including recurrent autoimmune diabetes mellitus, and will briefly discuss histopathological data available on islet transplantation.

Comparison of C4d detection on erythrocytes and PTC-C4d to histological signs of antibody-mediated rejection in kidney transplantation

C4d on erythrocytes (EC4d), C4d peritubular capillary deposition (PTC-C4d) staining and histology were compared in a cross-sectional cohort of 146 renal allograft biopsies (132 patients). EC4d levels paralleled PTC-C4d staining, but were more predictive of peritubular capillaritis (PTC). Donor-specific antibodies (DSA), PTC-C4d, EC4d and PTC were analyzed in an independent longitudinal follow-up cohort (96 biopsies, 76 patients). Seventy-six samples were PTC and EC4d concordant, 11 positive and 65 negative, 7 PTC-EC4d+ and 13 PTC+EC4d-. EC4d levels were related to DSA occurrence. With ABMR defined by PTC and DSA, all apparently discordant patients, EC4d negative, were correctly reassigned comparing EC4d level curves with rejection kinetics, with positive EC4d samples predating biopsy or late biopsies compared with ABMR flare-ups. All EC4d-positive patients without PTC or DSA had permanent high EC4d levels unrelated to rejection. EC4d was more abundant in PTC-positive (mean = 108.5%± 3.4; n = 50) than PTC-negative samples (mean = 88.1%± 1.3; n= 96; p < 0.0001). Sensitivity, specificity, positive predictive value and negative predictive value of PTC-C4d and EC4d for PTC were, respectively, 75%, 79%; 64%, 76% (p < 0.05); 28%, 46% (p < 0.05) and 93%, 94%. Values were similar for DSA. A noninvasive blood test, EC4d, and particularly longitudinally monitoring EC4d levels, may increase surrogate ABMR testing options.

Posttransplant donor-specific anti-HLA antibodies negatively impact pancreas transplantation outcome

During a 9-year follow-up, 167 consecutive pancreas transplant recipients (152 simultaneous pancreas-kidney [SPK]) were followed for the detection of posttransplant anti-HLA antibodies. Forty patients (24%) developed anti-HLA antibodies, 26 (65%) had donor-specific antibodies (DSA; 61% anticlass 2) and 14 (35%) non-DSA (78.6% anticlass 1). More rejection episodes were observed in patients with positive anti-HLA antibodies than in patients without antibodies (42.5% vs. 11%; p = 0.001), with the highest incidence observed in DSA patients (53.8%). More severe rejections (according to rescue therapy) were observed in DSA patients compared to non-DSA (p < 0.05) or to negative patients (p < 0.001). Contrasting with the kidney, pancreas graft survival did not differ between patients with or without anti-HLA antibodies. On the contrary, pancreas and kidney survivals were significantly lower in DSA positive patients (75% for both organs) as compared to non-DSA positive patients (100% for pancreas and 92% for kidney) or to HLA-negative patients (91% for pancreas and 89% for kidney). Nontechnical pancreas and kidney graft failures were significantly higher in positive than in negative anti-HLA patients (32.5% vs. 11%; p < 0.01). Occurrence of posttransplant DSA was an independent risk factor for both pancreas and kidney survival (HR 3.2; p = 0.039) in diabetic transplant recipients.

Plasma proteome changes associated with refractory cytopenia with multilineage dysplasia

BACKGROUND

Refractory cytopenia with multilineage dysplasia (RCMD) is a subgroup of myelodysplastic syndrome (MDS), which belongs to oncohematological diseases, occurring particularly in elderly patients, and represents a heterogeneous group of bone marrow diseases. The goal of this study was to look for plasma proteins that changed quantitatively or qualitatively in RCMD patients.

RESULTS

A total of 46 plasma samples were depleted, proteins were separated by 2D SDS-PAGE (pI 4-7), and proteomes were compared using Progenesis SameSpots statistical software. Proteins were identified by nanoLC-MS/MS. Sixty-one unique, significantly (p < 0.05, ANOVA) different spots were found; proteins in 59 spots were successfully identified and corresponded to 57 different proteins. Protein fragmentation was observed in several proteins: complement C4-A, complement C4-B, inter-alpha-trypsin inhibitor heavy chain H4, and endorepellin.

CONCLUSIONS

This study describes proteins, which change quantitatively or qualitatively in RCMD patients, and represents the first report on significant alterations in C4-A and C4-B complement proteins and ITIH4 fragments in patients with MDS-RCMD.

Guidelines for the diagnosis of antibody-mediated rejection in pancreas allografts-updated Banff grading schema

The first Banff proposal for the diagnosis of pancreas rejection (Am J Transplant 2008; 8: 237) dealt primarily with the diagnosis of acute T-cell-mediated rejection (ACMR), while only tentatively addressing issues pertaining to antibody-mediated rejection (AMR). This document presents comprehensive guidelines for the diagnosis of AMR, first proposed at the 10th Banff Conference on Allograft Pathology and refined by a broad-based multidisciplinary panel. Pancreatic AMR is best identified by a combination of serological and immunohistopathological findings consisting of (i) identification of circulating donor-specific antibodies, and histopathological data including (ii) morphological evidence of microvascular tissue injury and (iii) C4d staining in interacinar capillaries. Acute AMR is diagnosed conclusively if these three elements are present, whereas a diagnosis of suspicious for AMR is rendered if only two elements are identified. The identification of only one diagnostic element is not sufficient for the diagnosis of AMR but should prompt heightened clinical vigilance. AMR and ACMR may coexist, and should be recognized and graded independently. This proposal is based on our current knowledge of the pathogenesis of pancreas rejection and currently available tools for diagnosis. A systematized clinicopathological approach to AMR is essential for the development and assessment of much needed therapeutic interventions.

The significance of donor-specific HLA antibodies in rejection and ductopenia development in ABO compatible liver transplantation

The role of humoral alloreactivity in ABO-compatible liver transplantation remains unclear. To understand the significance of donor-specific HLA alloantibodies (DSA) in liver rejection, we applied the currently used strategy for detection of antibody-mediated rejection of other solid allografts. For this purpose we reviewed the data on 43 recipients of ABO identical/compatible donor livers who had indication liver biopsy stained for complement element C4d and contemporaneous circulating DSA determination. Seventeen (40%) patients had significant circulating DSA in association with diffuse portal C4d deposition (DSA+/diffuse C4d+). These DSA+/diffuse C4d+ subjects had higher frequency of acute cellular rejection (ACR) 15/17 versus 13/26 (88% vs. 50%), p = 0.02, and steroid resistant rejection 7/17 versus 5/26 (41% vs. 19%), p = 0.03. Based on detection of the combination DSA+/diffuse C4d+, 53.6% of cases of ACR had evidence of concurrent humoral alloreactivity. Six of the 10 patients with ductopenic rejection had circulating DSA and diffuse portal C4d, three of whom (2 early and 1 late posttransplantation) developed unrelenting cholestasis, necessitating specific antibody-depleting therapy to salvage the allografts. Thus, in ABO-compatible liver transplantation humoral alloreactivity mediated by antibodies against donor HLA molecules appears to be frequently intertwined with cellular mechanisms of rejection, and to play a role in ductopenia development.

Preserved endocrine function in a pancreas transplant recipient with pancreatic panniculitis and antibody-mediated rejection

Pancreas transplantation is an effective treatment option for patients with complicated diabetes mellitus. Pancreas allograft recipients are followed with laboratory markers such as serum amylase, lipase and glucose levels. Hyperglycemia may indicate severe acute rejection and has recently been associated with antibody-mediated (humoral) rejection. In this report, we describe a unique case of a pancreas-after-kidney (PAK) transplant recipient with the rare presentation of pancreatic panniculitis, biopsy-proven severe acute cellular and antibody-mediated pancreas allograft rejection and surprisingly well-preserved endocrine function despite treatment with high dose steroids. We discuss the clinicopathologic features of antibody-mediated pancreas rejection, including the importance of correlating pancreas allograft biopsy, C4d staining and donor specific antibodies, to diagnose antibody-mediated rejection and initiate the correct treatment.

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.