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.

Fetal pancreas transplants are dependent on prolactin for their development and prevent type 1 diabetes in syngeneic but not allogeneic mice.

Transplantation of adult pancreatic islets has been proposed to cure type 1 diabetes (T1D). However, it is rarely considered in the clinic because of its transient effect on disease, the paucity of donors, and the requirement for strong immunosuppressive treatment to prevent allogeneic graft rejection. Transplantation of fetal pancreases (FPs) may constitute an attractive alternative because of potential abundant donor sources, possible long-term effects due to the presence of stem cells maintaining tissue integrity, and their supposed low immunogenicity. In this work, we studied the capacity of early FPs from mouse embryos to develop into functional pancreatic islets producing insulin after transplantation in syngeneic and allogeneic recipients. We found that as few as two FPs were sufficient to control T1D in syngeneic mice. Surprisingly, their development into insulin-producing cells was significantly delayed in male compared with female recipients, which may be explained by lower levels of prolactin in males. Finally, allogeneic FPs were rapidly rejected, even in the context of minor histocompatibility disparities, with massive graft infiltration with T and myeloid cells. This work suggests that FP transplantation as a therapeutic option of T1D needs to be further assessed and would require immunosuppressive treatment.

Upregulation of IL-1ß, IL-6, and CCL-2 by a novel mouse model of pancreatic ischemia-reperfusion injury.

BACKGROUND: Little is known about the immunologic events surrounding pancreatic ischemia-reperfusion injury (IRI) because of a lack of established experimental models. The purpose of this study was to develop a mouse model for pancreatic IRI to serve as a basis for the immunologic characterization of pancreatic organ damage at transplantation. METHODS: Reversible ischemia was surgically induced by vascular isolation of the distal pancreas for 0, 10, 20, or 30 min. Mice receiving laparotomy without clamping served as sham-operated controls. After reperfusion, mice were serially assayed for biochemical and histologic evidence of inflammation, proinflammatory cytokine and chemokine production, and inflammatory gene upregulation. RESULTS: After induction of pancreatic IRI, serum amylase and lactate dehydrogenase peaked at 6 hr and returned to baseline by 120 hr after injury in all groups. Mice undergoing 30 min of IRI demonstrated the greatest biochemical evidence of inflammation. Histologic scoring similarly demonstrated marked inflammation in mice subjected to 30-min IRI compared with controls. Serum cytokine/chemokine analysis demonstrated significant upregulation of granulocyte colony-stimulating factor, interferon γ, tumor necrosis factor α, interleukin (IL)-2, IL-1ß, IL-6, chemokine (C-C motif) ligand-2, chemokine (C-C motif) ligand-5, chemokine (C-X-C motif) ligand-1, and macrophage inflammatory protein 2. A similar upregulation of ccl2, il1b, il6, fos, hspa1a, hspd1, and cd14 gene expression was detected by real-time polymerase chain reaction analysis of pancreatic tissue. CONCLUSIONS: This novel model of distal pancreatic IRI in the mouse demonstrates time-limited pancreatic inflammation and injury by histologic and biochemical indices. Inflammation may be, in part, a result of the immunologic effects of IL-1ß, IL-6, and CCL-2. This model provides a method by which immunologic mechanisms of pancreatic IRI can be elucidated.

Immunological monitoring after pancreas transplantation.

PURPOSE OF REVIEW: After switching from bladder to enteric drainage, pancreas graft monitoring, particularly after solitary transplantation, has become an important issue. The aim of this work was to systematically review the relevant literature with regard to various biomarkers, imaging techniques, and pathologic evaluation of allograft tissue. RECENT FINDINGS: More recent studies including graft histology demonstrate the low specificity of pancreatic enzymes as a marker of acute rejection. On the other hand, most blood and serum markers are indicative of an activated immune status rather than rejection. Interestingly, the concomitantly transplanted kidney from the same donor does not seem to be a reliable surrogate marker. Although computed tomography or ultrasound-guided percutaneous biopsies of the pancreas are performed more frequently at present, the complication rate is still as high as 11%. In contrast, cystoscopic and enteroscopic biopsies of the duodenal part of the graft are associated with almost no complications. The few clinical studies dealing with the duodenum as surrogate marker for the pancreas report a high correlation between duodenum mucosal and pancreas parenchymal histology. SUMMARY: Pancreatic graft parenchymal biopsy remains the gold standard in diagnosing pancreatic rejection, as clinical parameters, pancreatic enzymes, noninvasive biomarkers, and surrogate renal biopsies are not reliable tools. Endoscopically obtained duodenal cuff biopsies are a less invasive alternative to percutaneous biopsies.

Imaging after pancreatic surgery.

Pancreatic surgery, until the Whipple era in the early 1900s, was once regarded as calamitous by most surgeons. With advances in surgical techniques, operative mortality has been greatly reduced, although morbidity remains a significant problem. Knowledge of the surgical options for treatment of pancreatic neoplastic and inflammatory disease is important for the practicing radiologist, to anticipate and identify complications commonly sought and well depicted with imaging.

Long-term pancreatic allograft survival after renal retransplantation in prior simultaneous pancreas-kidney recipients.

Over a 23-year period, our center performed 82 renal retransplants in prior simultaneous pancreas-kidney recipients with functioning pancreatic allografts. All patients were insulin-independent at retransplantation. We aimed to quantify the risk of returning to insulin therapy and to identify factors that predispose patients to pancreatic allograft failure after renal retransplantation. Among these 82 patients, pancreatic allograft survival after renal retransplantation was 78%, 49% and 40% at 1, 5 and 10 years. When analyzing risk factors, we unexpectedly found no clear relationship between the cause of primary renal allograft failure, hemoglobin A1c (HbA1c) or fasting C-peptide level at retransplant and subsequent pancreatic allograft failure. An elevated HbA1c in the month after renal retransplant correlated with subsequent pancreatic graft loss and patients experiencing pancreatic graft loss were more likely to subsequently lose their renal retransplant. Although it is difficult to prospectively identify those patients who will return to insulin therapy after repeat renal transplantation, the relatively high frequency of this event mandates that this risk be conveyed to patients. Nonetheless, the survival benefit associated with renal retransplantation justifies pursuing retransplantation in this population.

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

PURPOSE OF REVIEW: 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. RECENT FINDINGS: 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 (±â€Šneutrophilic) 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)+. SUMMARY: 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.

Effects of octreotide on activated pancreatic stellate cell-induced pancreas graft fibrosis in rats.

BACKGROUND: Of solid organ transplantations, pancreas transplantation is associated with the highest incidence of pancreatic fibrosis in the early post-transplantation period. Activated pancreatic stellate cells (PSCs) are the main source of pancreatic fibrosis. Octreotide is widely used as a prophylactic for postoperative complications in pancreas transplant recipients. Recent studies have shown that it can inhibit liver fibrosis. This study investigated the effect of octreotide in pancreas graft fibrosis in rats. MATERIALS AND METHODS: Isolated PSCs from Sprague Dawley rats were co-cultured with different doses of octreotide (1.25, 2.5, 5, 10, 20, and 40 ng/mL). PSC proliferation was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide at 48, 72, and 96 h. The α-smooth muscle actin (α-SMA) and collagen I expressions of PSCs were detected by immunohistochemistry and reverse-transcriptase polymerase chain reaction. Rat heterotopic pancreaticoduodenal transplantation was performed with and without octreotide treatment (0.01 mg/kg). Pancreas grafts were harvested at postoperative d 1, 3, 5, and 7. Hematoxylin-eosin staining, Masson's trichrome staining, and immunohistochemical staining for α-SMA, collagen I, and tumor growth factor-ß1 (TGF-ß1) were performed. RESULTS: Octreotide at a concentration of >20 ng/mL significantly inhibited PSC activation and proliferation in vitro. Inflammatory infiltration was reduced in the octreotide group in vivo, and the expression levels of α-SMA, collagen I, and TGF-ß1 were also lower, with statistic significant difference or not. Masson's trichrome staining showed a decrease in collagen deposition with octreotide treatment. CONCLUSIONS: Octreotide effectively inhibits PSC activation and proliferation in vitro, but has a limited inhibitory effect on the development of pancreas graft fibrosis.

Increased CD64 expression on polymorphonuclear neutrophils indicates infectious complications following solid organ transplantation.

The aim of this study was to evaluate the diagnostic value of monitoring CD64 antigen upregulation on polymorphonuclear neutrophils (PMN) for the identification of infectious complications in the postoperative course of solid organ transplanted patients. Twenty-five kidney, 13 liver, and four pancreas-kidney transplanted patients were included. Beginning with preoperative values up to postoperative values after 3 months for each patient, the PMN CD64 Index, HLA-DR on monocytes, NKp44+ NK and NK/T cells, CXCR3+ NK cells, CXCR3+ T helper cells, CXCR3+ NK/T cells, and CD4/CD8 ratio were measured by flow cytometry. Subsequently they were correlated with confirmed postoperative complications. Measuring the PMN CD64 Index reached a sensitivity of 89% and a specificity of 65% in the detection of infectious complications. Concerning this matter, it was a significantly better marker than all other included parameters except CXCR3+ NK/T cells. In contrast, according to our results the PMN CD64 Index has no diagnostic relevance in detection of rejections. The combination of included parameters showed no improved diagnostic value. Due to its high sensitivity and specificity for infectious complications CD64 on PMN could be proven a very good indicator in evaluating suspected infectious complications in the postoperative course of transplanted patients.

[Small intestine, pancreas and islet cell transplantation]. / Dünndarm-, Pankreas- und Inselzelltransplantation.

The past decade has seen substantial improvements in patient and graft survival after intestinal transplantation. This improvement has been achieved by advances in donor and recipient selection, patient management, immunosuppression and surgical techniques. Intestinal transplantation is therefore considered a therapeutic option in the treatment of short bowel syndrome. Mile stones include the development of the calcineurin inhibitor Tacrolimus for immunosuppression as well as induction therapy using immune modulating substances like interleukin-2 receptor antagonists and antilymphocyte preparations. In addition to improvements in immunosuppression, antimicrobial prophylaxis and diagnosis of rejection, advances in surgical techniques have been crucial to achieving increased graft survival. Pancreas transplantation, generally with simultaneous kidney transplantation, is now available as a treatment option for patients with labile diabetes mellitus (usually type 1). Allogeneic islet transplantation was developed in the 1990s as a minimally invasive alternative to pancreas transplantation. Pancreatic islets are isolated enzymatically from the donor pancreas, in most cases infused into the portal vein and thus engrafted into the liver. Currently, technical and medical problems as well as high costs prevent the application of islet transplantation as a therapeutic option for a larger number of patients with diabetes mellitus.

Usefulness of 3-month protocol biopsy of kidney allograft to detect subclinical rejection under triple immunosuppression with basiliximab: a single center experience.

BACKGROUND: Theoretically, an early protocol biopsy (PB) serves to detect subclinical rejection (SCR), allowing early treatment and prevention of acute rejection (AR) and chronic graft injuries. In this retrospective study, we investigated the incidence of biopsy-proven AR (BPAR) and the usefulness of a 3-month PB in detecting SCR in kidney transplant (KT) and simultaneous pancreas-kidney transplant (SPKT) recipients who received triple immunosuppression and basiliximab. METHODS: Between January 2007 and September 2009, 116 patients received transplantation (KT = 112, SPKT = 4). In August 2008, we changed our PB policy and started to collect PB after 3 months instead of a pre-discharge biopsy performed 1 month after transplantation. Here we compare the incidence of SCR (defined as Banff grade Ia or higher) between the pre-discharge PB group and the 3-month PB group. PB was obtained from 41 patients before discharge (pre-discharge PB group), and from 49 patients 3 months after transplantation (3-month PB group). RESULTS: Among all recipients, 21 patients were diagnosed with BPAR (estimated incidence of BPAR 20.1%); including 13 (62.0%) diagnosed from 31 to 180 postoperative days (POD), and only 3 (14.3%) within 30 POD. The incidence of BPAR was not different between the two groups (19.5 and 20.8%, respectively); however, 4 of 8 recipients in the 3-month PB group were diagnosed with SCR, compared to none in the pre-discharge PB group (P < 0.05). CONCLUSION: Since the use of triple immunosuppression and basiliximab delayed the onset of AR, we recommend that in order to detect SCR, PB should be obtained 3 months postoperatively.

Expression of secretory phospholipase A 2 in insulitis of human transplanted pancreas and its insulinotropic effect on isolated rat islets.

The expression of secretory phospholipase A 2 (sPLA 2) is induced by inflammatory stimuli in various cells, and sPLA 2 contribute to produce proinflammatory lipid mediators via hydrolyzing plasma membrane phospholipids into free fatty acid and lysophospholipid. We studied the expression of group IIA sPLA 2 in human islets of transplanted pancreas before and after the recurrence of type 1 diabetes mellitus in a case study. In addition, the effects of exogenous sPLA 2 in isolated rat islets were investigated. Expression of group IIA sPLAs was immunohistochemicaly investigated in the pancreas graft biopsy specimens. Insulin secretion was evaluated by static incubation with different concentrations of snake venom sPLA 2. Intracellular free Ca ( 2) + concentration was measured with Fura 2 and lysophosphatidylcholine (LPC) contents in islets were determined by electrospray ionization-liquid chromatography/mass spectrometry. Group IIA sPLA 2 was not expressed in islets without insulitis before the recurrence, whereas it was diffusely expressed in islets after the recurrence with insulitis. There were cells co-expressing group IIA sPLA 2 and insulin. sPLA 2 dose-dependently induced insulin secretion in isolated rat islets, which was completely prevented by a specific sPLA 2 inhibitor indoxam. The application of sPLA 2 did not affect intracellular free Ca ( 2) + concentration in ß cells. On the other hand, LPC contents in islets were significantly increased in sPLA 2-treated islets compared with untreated islets. Incubation with indoxam suppressed the sPLA 2-induced increase of LPC. In conclusion, the present study suggests that group IIA sPLA 2 may be expressed in islets during insulitis in humans. Although sPLA 2 induced insulin secretion in vitro probably via the production of lysophospholipid, the significance of this enzyme expression in insulitis remains elusive.

Histologic features of cytomegalovirus enteritis in small bowel allografts.

BACKGROUND: Cytomegalovirus (CMV) is one of the most common viral infections to affect solid organ transplant patients, most frequently owing to reactivation of a latent infection as a result of immunosuppression. CMV enteritis (CE) may enter into the differential diagnosis of acute rejection in biopsies of small bowel (SB) allografts, where differentiation is important due to disparate therapies. OBJECTIVE: The aim of this study was to identify histologic features in SB allografts that may suggest CE. METHODS: The case files for a single institution were queried for all cases of SB mucosal biopsies with cells positive by CMV immunoperoxidase staining. Morphologic and clinical information was reviewed. RESULTS: Six biopsies demonstrating immunoperoxidase-confirmed CE were identified in a retrospective review of the records of a single institution. A common predisposing factor was the administration of high-dose steroids within a month before CE diagnosis. Most cases (66%) displayed a demarcated area of villous/crypt loss with an abundance of plasma cells and lymphocytes and a paucity of eosinophils. One case showed an acute enteritis-like pattern of injury, corresponding with a higher number of CMV-positive cells. CMV inclusions were visible on hematoxylin-eosin stains in all but 1 case. In no case were histologic criteria for acute cellular rejection met. CONCLUSIONS: The presence of circumscribed area of mucosal injury with few eosinophils or an acute enteritis pattern should prompt the identification of viral inclusions or the acquisition of a CMV immunostain.

Correlation between angiogenesis and islet graft function in diabetic mice: magnetic resonance imaging assessment.

BACKGROUND/PURPOSE: Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) was used to evaluate neovascularization after intravenous injection of gadolinium, where contrast leaks out of new vessels and remains within the tissues. We examined the relationship between DCE-MRI and metabolic parameters such as blood glucose, serum insulin and glucose tolerance test (GTT) after intraportal islet transplantation. METHODS: Streptozotocin-induced diabetic BALB/c mice (n = 15) received syngeneic intraportal islet transplantation (500 islet equivalent). Blood glucose, serum insulin and GTT were evaluated till postoperative day (POD) 14. Liver DCE-MRI was performed at POD 3, 7 and 14. Correlations between DCE-MRI and metabolic parameters were examined using regression analysis. RESULTS: Eight mice achieved normoglycemia after intraportal transplantation. At POD 3 a significant but moderate correlation between DCE-MRI and blood glucose was found. No DCE-MRI or metabolic parameters correlated at POD 7. However, at POD 14 strong or moderate correlations between DCE-MRIs were found: negative correlations with blood glucose (R (2) = 0.86) and GTT (R (2) = 0.48) but a positive correlation with serum insulin (R (2) = 0.32). CONCLUSION: We report that DCE-MRI can reflect the metabolic and functional condition of the transplanted islets.

Islets of Langerhans are protected from inflammatory cell recruitment during reperfusion of rat pancreas grafts.

BACKGROUND: Ischemia/reperfusion (I/R) injury plays a pivotal role in the development of graft pancreatitis, with ischemia time representing one of its crucial factors. However, it is unclear, whether exocrine and endocrine tissue experience similar inflammatory responses during pancreas transplantation (PTx). This study evaluated inflammatory susceptibilities of islets of Langerhans (ILH) and exocrine tissue after different preservation periods during early reperfusion. METHODS: PTx was performed in rats following 2 h (2h-I) or 18 h (18h-I) preservation. Leukocyte-endothelial cell interactions (LEI) were analyzed in venules of acinar tissue and ILH in vivo over 2 h reperfusion. Nontransplanted animals served as controls. Tissue samples were analyzed by histomorphometry. RESULTS: In exocrine venules leukocyte rolling predominated in the 2h-I group. In the 18h-I group, additionally, high numbers of adherent leukocytes were found. Histology revealed significant edema formation and leukocyte extravasation in the 18h-I group. Notably, LEI in postcapillary venules of ILH were significantly lower. Leukocyte rolling was only moderately enhanced and few leukocytes were found adherent. Histology revealed minor leukocyte extravasation. CONCLUSION: Ischemia time contributes decisively to the extent of the I/R-injury in PTx. However, ILH have a significantly lower susceptibility towards I/R, even when inflammatory reactions in adjacent exocrine tissue are evident.

Pancreas allograft rejection: analysis of concurrent renal allograft biopsies and posttherapy follow-up biopsies.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Pancreas transplant: recent advances and spectrum of features in pancreas allograft pathology.

As result of improved surgical techniques and newer immunosuppressive regimens contributing significantly to better graft survival, exocrine pancreas transplantation remains the standard treatment of choice for patients with diabetes mellitus complicated by end-stage renal disease. Histologic assessment continues to play an important role in the diagnosis of graft complications after pancreas transplantation, especially for evaluating allograft rejection where histopathology is still considered the gold standard. This review elaborates on the current types of pancreas transplants and focuses on the patterns of allograft injury that are encountered in posttransplantation pancreas biopsies along with the pertinent differential diagnoses. In addition to optimal histologic assessment, as in any other organ transplant setting, clinical information including indication and duration of transplant as well as other serologic work-up must be taken into consideration during clinical decision making for optimal graft outcome.