Effector T cell function rather than survival determines extent and duration of hepatitis in mice.

BACKGROUND & AIMS: Acute hepatitis is often mediated by cytotoxic T lymphocytes (CTLs); however, the intrinsic parameters that limit CTL-mediated liver injury are not well understood. METHODS: To investigate whether acute liver damage is limited by molecules that decrease the lifespan or effector function of CTLs, we used a well-characterized transgenic (Tg) mouse model in which acute liver damage develops upon transfer of T cell receptor (TCR) Tg CD8 T cells. Recipient Tg mice received donor TCR Tg T cells deficient for either the pro-apoptotic molecule Bim, which regulates CTL survival, or suppressor of cytokine signaling-1 (SOCS-1), which controls expression of common gamma chain cytokines; the effects of anti-PD-L1 neutralizing antibodies were also assessed. RESULTS: Use of Bim-deficient donor T cells and/or PD-L1 blockade increased the number of intrahepatic T cells without affecting the degree and kinetic of acute hepatitis. In contrast, SOCS-1-deficient T cells induced a heightened, prolonged acute hepatitis caused by their enhanced cytotoxic function and increased expansion. Although they inflicted more severe acute liver damage, SOCS-1-deficient T cells never precipitated chronic hepatitis and became exhausted. CONCLUSIONS: The degree of acute hepatitis is regulated by the function of CD8 T cells, but is not affected by changes in CTL lifespan. Although manipulation of the examined parameters affected acute hepatitis, persistent hepatitis did not ensue, indicating that, in the presence of high intrahepatic antigen load, changes in these factors in isolation were not sufficient to prevent T cell exhaustion and mediate progression to chronic hepatitis.

Long-term results after in-situ split (ISS) liver resection.

PURPOSE: In-situ split (ISS) liver resection is a novel method to induce rapid hypertrophy of the contralateral liver lobe in patients at risk for postoperative liver failure due to insufficient liver remnant. So far, no data about oncological long-term survival after ISS liver resection is available. METHODS: We retrospectively analyzed our patients treated with ISS liver resection at the Department of Surgery of the University of Regensburg, the first center worldwide to perform ISS. RESULTS: Between 2007 and 2014, ISS liver resection was performed in 16 patients. Two patients (12.5 %) were lost in early postoperative phase (90 days) and one was lost to follow-up. Thirteen patients with a follow-up period of more than 3 months were included into oncologically focused analyses. Median follow-up was 26.4 months (range 3.2-54.6). Seven patients had suffered from colorectal liver metastases (CRLM) and six from various other liver malignancies (non-CRLM). The ISS procedure had led to a median increase of 86.3 % of the left lateral liver lobe after a median of 9 days (range 4-28 days). Median disease-free survival (DFS) was 14.6 months and median overall survival (OS) was 41.7 months (26.4 months when including 90-days mortality). Three-year survival was calculated with 56.4 and 48.9 % when including perioperative mortality, respectively (CRLM 64.3 % vs. non-CRLM 50 %). CONCLUSION: ISS liver resection can provide long-term survival of selected patients with advanced liver malignancies that otherwise are not eligible for liver resection due to insufficient liver remnant.

Long-term oncologic outcome after laparoscopic surgery for rectal cancer.

BACKGROUND: Recent studies demonstrated favorable short- and mid-term results after laparoscopic surgery for rectal cancer. However, long-term results from large series are lacking. The present study analyses long-term results of laparoscopic rectal cancer surgery from a large-volume center. METHODS: From January 1998 until March 2005, 225 patients underwent laparoscopic rectal resection due to carcinoma at the Medical Centre of the University of Regensburg. From 224 patients, a follow-up over 10 years was performed using the data of the Tumour Centre of the University of Regensburg. The data were analysed using oncological data (tumour recurrence) as well as overall survival. In addition, the effect of conversion to open resection on overall survival was analysed. RESULTS: With a median of 10 years at follow-up, the overall and disease-free survival was 50.5 and 50.1 %, respectively. Local recurrence of all patients was 5.8 % and none of the converted patients was within this group. The median time interval for the development of local recurrence was 30 months. Six of the 13 patients with local recurrence (46.1 %) had received neoadjuvant radiochemotherapy before surgery. Patients with a conversion to open surgery had primarily a significantly worse outcome than patients resected completely laparoscopically (p = 0.003). However, this difference was no longer apparent using a multivariant analysis (hazard ratio 1.221; p = 0.478). CONCLUSIONS: Overall survival and local recurrence rate of patients undergoing laparoscopic resection of rectal cancer are comparable to open surgery. However, in our analysis, patients undergoing laparoscopic anterior resection had a higher survival rate compared with patients with abdominoperineal resection.

Hepatocyte entry leads to degradation of autoreactive CD8 T cells.

Although most self-reactive T cells are eliminated in the thymus, mechanisms to inactivate or control T cells specific for extrathymic antigens are required and exist in the periphery. By investigating the site in which autoreactive T cells are tolerized, we identify a unique mechanism of peripheral deletion in which naïve autoreactive CD8 T cells are rapidly eliminated in the liver after intrahepatic activation. T cells actively invade hepatocytes, enter endosomal/lysosomal compartments, and are degraded. Blockade of this process leads to accumulation of autoreactive CD8 T cells in the liver and breach of tolerance, with the development of autoimmune hepatitis. Cell into cell invasion, or emperipolesis, is a long-observed phenomenon for which a physiological role has not been previously demonstrated. We propose that this "suicidal emperipolesis" is a unique mechanism of autoreactive T-cell deletion, a process critical for the maintenance of tolerance.

Retrograde stapling of a free cervical jejunal interposition graft: a technical innovation and case report.

BACKGROUND: Free jejunal interposition is a useful technique for reconstruction of the cervical esophagus. However, the distal anastomosis between the graft and the remaining thoracic esophagus or a gastric conduit can be technically challenging when located very low in the thoracic aperture. We here describe a modified technique for retrograde stapling of a jejunal graft to a failed gastric conduit using a circular stapler on a delivery system. CASE PRESENTATION: A 56 year-old patient had been referred for esophageal squamous cell carcinoma at 20 cm from the incisors. On day 8 after thoracoabdominal esophagectomy with gastric pull-up, an anastomotic leakage was diagnosed. A proximal-release stent was successfully placed by gastroscopy and the patient was discharged. Two weeks later, an esophagotracheal fistula occurred proximal to the esophageal stent. Cervical esophagostomy was performed with cranial closure of the gastric conduit, which was left in situ within the right hemithorax. Three months later, reconstruction was performed using a free jejunal interposition. The anvil of a circular stapler (Orvil®, Covidien) was placed transabdominally through an endoscopic rendez-vous procedure into the gastric conduit. A free jejunal graft was retrogradely stapled to the proximal end of the conduit. Microvascular anastomoses were performed subsequently. The proximal anastomosis of the conduit was completed manually after reperfusion. CONCLUSIONS: This modified technique allows stapling of a jejunal interposition graft located deep in the thoracic aperture and is therefore a useful method that may help to avoid reconstruction by colonic pull-up and thoracotomy.

Rationale and prospects of mesenchymal stem cell therapy for liver transplantation.

PURPOSE OF REVIEW: Despite their potential to supplement the donor organ pool, expanded donor criteria grafts are associated with an elevated risk of graft failure and increased early mortality. Likewise, attempts to promote operational graft tolerance through conventional immunosuppressive therapy have demonstrated significant safety-related drawbacks. Because of their potent regenerative and immunomodulative potential, adjunct mesenchymal stem cell (MSC) therapy represents an innovative approach to both of these clinical problems. RECENT FINDINGS: Recent studies have begun to delineate the benefit and mechanisms of short-term therapy combining MSCs and low-dose immunosuppressive drugs in promoting graft acceptance and potentially regeneration. SUMMARY: The current review presents our rationale for the first-in-man clinical trial in liver transplantation utilizing a mesenchymal cell product (MultiStem, Athersys, Cleveland, Ohio, USA). The long-term objective of this program is to safely minimize the dose of complementary immunosuppressive drugs while achieving long-term allograft survival and operational tolerance. The use of adjunct cellular therapy as a means of reducing long-term pharmacotherapy would represent a major advancement in the field of liver transplantation.

Differential migration of passenger leukocytes and rapid deletion of naive alloreactive CD8 T cells after mouse liver transplantation.

Donor passenger leukocytes (PLs) from transplanted livers migrate to recipient lymphoid tissues, where they are thought to induce the deletion of donor-specific T cells and tolerance. Difficulties in tracking alloreactive T cells and PLs in rats and in performing this complex surgery in mice have limited progress in identifying the contribution of PL subsets and sites and the kinetics of T cell deletion. Here we developed a mouse liver transplant model in which PLs, recipient cells, and a reporter population of transgenic CD8 T cells specific for the graft could be easily distinguished and quantified in allografts and recipient organs by flow cytometry. All PL subsets circulated rapidly via the blood as soon as 1.5 hours after transplantation. By 24 hours, PLs were distributed differently in the lymph nodes and spleen, whereas donor natural killer and natural killer T cells remained in the liver and blood. Reporter T cells were activated in both liver and lymphoid tissues, but their numbers dramatically decreased within the first 48 hours. These results provide the first unequivocal demonstration of the differential recirculation of liver PL subsets after transplantation, and show that alloreactive CD8 T cells are deleted more rapidly than initially reported. This model will be useful for dissecting early events leading to the spontaneous acceptance of liver transplants.

Naïve CD8 T cell activation by liver bone marrow-derived cells leads to a "neglected" IL-2low Bimhigh phenotype, poor CTL function and cell death.

BACKGROUND & AIMS: The occurrence of primary CD8 T cell activation within the liver, unique among the non-lymphoid organs, is now well accepted. However, the outcome of intrahepatic T cell activation remains controversial. We have previously reported that activation initiated by hepatocytes results in a tolerogenic phenotype characterized by low expression of CD25 and IL-2, poor cytotoxic T lymphocyte (CTL) function, and excessive expression of the pro-apoptotic protein Bim. METHODS: To investigate whether this phenotype was due to activation in the absence of co-stimulation, we generated bone marrow (bm) radiation chimeras in which adoptively transferred naïve transgenic CD8 T cells were activated in the presence of co-stimulation by liver bm-derived cells. RESULTS: Despite expressing pro-inflammatory cytokines, high levels of CD25 and CD54, donor T cells activated by liver bm-derived cells did not produce detectable IL-2 and displayed poor CTL function, suggesting incomplete acquisition of effector function. Simultaneously, these cells expressed high levels of Bim and died by neglect. Transfer of Bim-deficient T cells resulted in increased T cell numbers. CONCLUSIONS: These results imply that expression of CD25 and CD54 is co-stimulation dependent and distinguishes T cell activated by hepatocytes and liver bm-derived cells. In contrast, low expression of IL-2, poor CTL function and excess Bim production represent a more universal phenotype defining T cells undergoing primary activation by both types of hepatic antigen presenting cells (APC). These results have important implications for transplantation, in which all liver antigen presenting cells contribute to activation of T cells specific for the allograft.

Different approaches for complete mobilization of the splenic flexure during laparoscopic rectal cancer resection.

PURPOSE: Laparoscopic resection of rectal cancer has already become the standard procedure in many hospitals. The splenic flexure mobilization (SFM) is an important preparational step. Several methods are used for laparoscopic SFM; however, studies comparing different approaches are lacking. In the present study, three different approaches for SFM have been compared to each other. METHODS: Between January 1998 and December 2010, 415 patients with rectal adenocarcinoma underwent laparoscopic rectal resection at one center. Of these, 303 patients received complete splenic flexure mobilization. The SFM was performed using either a medial (SFM-M; n = 41), lateral (SFM-L; n = 214), or anterior (SFM-A; n = 48) approach. RESULTS: There was a significantly higher rate of intraoperative complications in the SFM-L group as compared to the SFM-M or the SFM-A group (p = 0.038). Postoperative surgical complications occurred in 5 (10.6 %) patients of the SFM-A group compared to 38 patients (17.7 %) in the SFM-L group (p = 0.002) and 5 (12.1 %) patients in the SFM-M group (p = 0.037). SFM-L was also associated with a higher frequency of overall postoperative morbidity which was mainly due to wound infection rates (p = 0.001). CONCLUSIONS: The anterior approach for SFM in laparoscopic surgery seems to be associated with lower frequency of intra- and postoperative morbidity.

Safety and feasibility of third-party multipotent adult progenitor cells for immunomodulation therapy after liver transplantation--a phase I study (MISOT-I).

BACKGROUND: Liver transplantation is the definitive treatment for many end-stage liver diseases. However, the life-long immunosuppression needed to prevent graft rejection causes clinically significant side effects. Cellular immunomodulatory therapies may allow the dose of immunosuppressive drugs to be reduced. In the current protocol, we propose to complement immunosuppressive pharmacotherapy with third-party multipotent adult progenitor cells (MAPCs), a culture-selected population of adult adherent stem cells derived from bone marrow that has been shown to display potent immunomodulatory and regenerative properties. In animal models, MAPCs reduce the need for pharmacological immunosuppression after experimental solid organ transplantation and regenerate damaged organs. METHODS: Patients enrolled in this phase I, single-arm, single-center safety and feasibility study (n = 3-24) will receive 2 doses of third-party MAPCs after liver transplantation, on days 1 and 3, in addition to a calcineurin-inhibitor-free "bottom-up" immunosuppressive regimen with basiliximab, mycophenolic acid, and steroids. The study objective is to evaluate the safety and clinical feasibility of MAPC administration in this patient cohort. The primary endpoint of the study is safety, assessed by standardized dose-limiting toxicity events. One secondary endpoint is the time until first biopsy-proven acute rejection, in order to collect first evidence of efficacy. Dose escalation (150, 300, 450, and 600 million MAPCs) will be done according to a 3 + 3 classical escalation design (4 groups of 3-6 patients each). DISCUSSION: If MAPCs are safe for patients undergoing liver transplantation in this study, a phase II/III trial will be conducted to assess their clinical efficacy.

Role of the hepatic parenchyma in liver transplant tolerance: a paradigm revisited.

Unlike other solid organs, liver transplants are spontaneously accepted in a wide range of animal models. In the clinic, transplanted livers also display privileged immunological properties allowing weaning of immunosuppression therapy in up to 20% of selected patients. To explain this phenomenon, many studies have focused on the role of donor-derived 'passenger' leukocytes that are thought to induce antigen-specific tolerance by migrating from the graft into recipient secondary lymphoid tissues. Although convincing evidence exists that these cells are able to elicit antiallograft T cell hyporesponsiveness, several studies argue against an exclusive role for this cell population and even question whether it is critical in conferring donor MHC-specific tolerance. Instead, these studies suggest that the hepatic parenchyma plays a more critical role in this phenomenon. In this review we will reinterpret the results of old and more recent literature in light of recent advances in the field of liver immunology to explain the contribution of both passenger leukocytes and liver tissue in the liver tolerance effect.

The impact of poloxamer 407 on the ultrastructure of the liver and evidence for clearance by extensive endothelial and kupffer cell endocytosis.

Poloxamer 407 (P407) is a non-ionic detergent that is used widely in pharmaceutical formulations and personal care products. In animals, P407 causes hyperlipidaemia. P407 is taken up by the liver and causes loss of fenestrations in liver sinusoidal endothelial cells (LSEC), which contributes to the pathogenesis of hyperlipidaemia. Here the short-term (1-15 days) effects of P407 on all liver cells were investigated in mice using electron and light microscopy. As expected, P407 was associated with hyperlipidaemia. Kupffer cells became massively engorged with vacuoles and took on a marked honeycomb morphology. LSECs also became engorged with vacuoles and endocytosis was activated. The diameter of lipoproteins in the space of Disse was less than those in the lumen, consistent with a filtering effect of fenestrations. Defenestration of the LSEC was noted. Hepatocyte endocytosis of lipoproteins and P407 particles was also noted; however, hepatocyte steatosis was not evident. Hepatic stellate cells did not appear to be abnormal. In conclusion, P407 is taken up by the liver mostly through endocytosis by LSECs and Kupffer cells.

Invading macrophages play a major role in the liver progenitor cell response to chronic liver injury.

BACKGROUND & AIMS: Although a strong association between liver progenitor cells (LPCs) and inflammation exists in many chronic liver diseases, the exact role of the immune system in LPC-mediated hepatic regeneration remains unclear. A number of pro-inflammatory factors were identified in cytokine knockout mice in which the LPC response was attenuated but neither the mechanism nor the producing cells are known. METHODS: To identify the critical immune cells and cytokines required in the LPC response, we compared two diet-induced models of liver injury with two recently established transgenic models of immune-mediated hepatitis. RESULTS: Despite severe inflammation being observed in all models, the generation of LPCs was highly dependent on the cause and kinetics of liver damage. The LPC response was associated with an increase of macrophages and CD8(+) T cells but not natural killer cells. T cell-deficient mice were able to mount a LPC response, albeit delayed, suggesting that T cells are not essential. Mice mounting an LPC response showed elevated numbers of Kupffer cells and invading CX(3)CR1(high)CCR2(high) macrophages secreting persistent high levels of tumour necrosis factor alpha (TNFalpha), a major cytokine involved in the LPC response. CONCLUSIONS: Liver macrophages are an important determinant of LPC expansion during liver regeneration in models of diet- and immune-mediated liver injury. Invading macrophages in particular provide pro-mitogenic cytokines such as TNFalpha that underpin the process. LPC themselves are a source of chemokines (CCL2, CX(3)CL1) that attract infiltrating macrophages.

Intrahepatic murine CD8 T-cell activation associates with a distinct phenotype leading to Bim-dependent death.

BACKGROUND & AIMS: Chronic infections by hepatotropic viruses such as hepatitis B and C are generally associated with an impaired CD8 T-cell immune response that is unable to clear the virus. The liver is increasingly recognized as an alternative site in which primary activation of CD8 T cells takes place, a property that might explain its role in inducing tolerance. However, the molecular mechanism by which intrahepatically activated T cells become tolerant is unknown. Here, we investigated the phenotype and fate of naïve CD8 T cells activated by hepatocytes in vivo. METHODS: Transgenic mouse models in which the antigen is expressed in lymph nodes and/or in the liver were adoptively transferred with naïve CD8 T cells specific for the hepatic antigen. RESULTS: Liver-activated CD8 T cells displayed poor effector functions and a unique CD25(low) CD54(low) phenotype. This phenotype was associated with increased expression of the proapoptotic protein Bim and caspase-3, demonstrating that these cells are programmed to die following intrahepatic activation. Importantly, we show that T cells deficient for Bim survived following intrahepatic activation. CONCLUSIONS: This study identifies Bim for the first time as a critical initiator of T-cell death in the liver. Thus, strategies inhibiting the up-regulation of this molecule could potentially be used to rescue CD8 T cells, clear the virus, and reverse the outcome of viral chronic infections affecting the liver.

Mesenchymal Stem Cells in Solid Organ Transplantation (MiSOT) Fourth Meeting: lessons learned from first clinical trials.

The Fourth Expert Meeting of the Mesenchymal Stem Cells in Solid Organ Transplantation (MiSOT) Consortium took place in Barcelona on October 19 and 20, 2012. This meeting focused on the translation of preclinical data into early clinical settings. This position paper highlights the main topics explored on the safety and efficacy of mesenchymal stem cells as a therapeutic agent in solid organ transplantation and emphasizes the issues (proper timing, concomitant immunossupression, source and immunogenicity of mesenchymal stem cells, and oncogenicity) that have been addressed and will be followed up by the MiSOT Consortium in future studies.

Liver tolerance and the manipulation of immune outcomes.

In recent years it has become apparent that the liver holds a distinct immunological position. Previously described as a "graveyard" for T cells activated in the periphery, emerging evidence indicates that this organ may have a more active role in mediating tolerance. Attenuated immune responses in the liver can be beneficial in the transplantation setting, as liver transplants are more readily accepted than other organ allografts even in the absence of immunosuppressive drugs. However, the ability of the liver to induce immunological unresponsiveness could be exploited by some pathogens, such as the hepatitis C virus (HCV), to establish chronic infections with potentially fatal outcomes. Understanding the mechanisms controlling the balance between intrahepatic tolerance and immunity is critical in order to design new strategies to enhance acceptance of solid organ allografts and to promote efficient immune responses against HCV. In this article, we will review current knowledge of the mechanisms regulating intrahepatic immunity and discuss how these mechanisms might potentially be targeted to achieve advantageous clinical outcomes in transplantation and persistent hepatotropic infections.

T cells in the liver: there is life beyond the graveyard.

Influenza A virus infection of C57BL/6 mice is a well-characterized model for studying CD8+ T cell-mediated immunity. Analysis of primary and secondary responses showed that the liver is highly enriched for CD8+ T cells specific for the immunodominant H2D(b)NP(366-374) (D(b)NP(366)) epitope. Functional analysis established that these liver-derived virus-specific CD8+ T cells are fully competent cytotoxic effectors and IFN-gamma secretors. In addition, flow cytometric analysis of early apoptotic cells showed that these influenza-specific CD8+ T cells from liver are as viable as those in the spleen, bronchoalveolar lavage, mediastinal lymph nodes, or lung. Moreover, cytokine profiles of the influenza-specific CD8+ T cells recovered from different sites were consistent with the bronchoalveolar lavage, rather than liver population, being the most susceptible to activation-induced cell death. Importantly, adoptively transferred influenza virus-specific CD8+ T cells from the liver survived and were readily recalled after virus challenge. Together, these results show clearly that the liver is not a "graveyard" for influenza virus-specific CD8+ T cells.

The liver: a special case in transplantation tolerance.

Liver transplants are not often rejected in patients weaned from immunosuppression and are spontaneously accepted in some animal models. We review past and recent findings of liver transplantation and propose a unified model in which several mechanisms act in concert to induce and maintain tolerance in both naïve and effector T cell compartments. First, passenger leukocytes migrate to lymphoid tissues and induce apoptosis of alloreactive naïve T cells. Second, antigen-specific activation and subsequent deletion of naïve and effector cells within the liver itself purge the repertoire of alloreactive T cells. Other mechanisms such as microchimerism and migration of donor dendritic cells to the thymus may play a predominant role in maintaining tolerance, and soluble major histocompatibility complex molecules, donor peptides, and regulatory T cells may participate in the induction and maintenance phases. Thus, the major challenge in liver transplantation will be to favor these tolerogenic processes while developing strategies that specifically inhibit alloreactive memory T cells.

Marked changes of the hepatic sinusoid in a transgenic mouse model of acute immune-mediated hepatitis.

BACKGROUND/AIMS: The liver sinusoidal endothelial cell (LSEC) is increasingly recognized as having an important role in hepatic immunity. However, the responses of LSECs and the hepatic sinusoid in immune-mediated hepatitis are poorly described. METHODS: We studied a transgenic mouse model of acute immune-mediated hepatitis: Met-Kb mice injected with T cells from Des-TCR mice. RESULTS: Hepatitis was characterized by lymphocyte infiltrates causing severe but transient liver damage. There were marked changes in the ultrastructure of the LSEC five days after injection of the T cells that coincided with the peak of the hepatitis. The porosity of fenestrations in the LSEC decreased and the endothelium became thickened. LSECs appeared to be markedly activated. These changes were associated with narrowing of the space of Disse, loss of hepatocellular microvilli and deposition of basal lamina. Lymphocytes were seen passing through fenestrations. Loss of fenestration in the LSEC prevented hepatitis induced by a second injection of lymphocytes on day 5. CONCLUSIONS: Structural changes in the LSEC occur during the peak of a mouse model of immune-mediated hepatitis. These changes were associated with attenuation of subsequent liver damage, suggesting that they may influence immunological responses mediated by LSECs or the passage of lymphocytes through LSEC fenestrations.