Weaning of immunosuppression in long-term liver transplant recipients

HLA-G level on monocytoid dendritic cells correlates with regulatory T-cell Foxp3 expression in liver transplant tolerance

BACKGROUND

Human leukocyte antigen (HLA)-G is a nonclassical HLA class I molecule expressed as membrane-bound and soluble isoforms. Interaction of HLA-G with its receptor, immunoglobulin-like transcript 4 on dendritic cells (DCs) down-regulates their T-cell stimulatory ability.

METHODS

We examined expression of HLA-G, immunoglobulin-like transcript 4, other immune regulatory molecules (inducible costimulator ligand and glucocorticoid-induced tumor necrosis factor-related receptor ligand), and the activation marker CMRF44 on circulating monocytoid dendritic cell (mDC) and plasmacytoid dendritic cell by monoclonal antibody staining and flow cytometry. Three groups of stable liver transplant recipients: operationally tolerant (TOL), prospective immunosuppressive drug weaning, and maintenance immunosuppression (MI) were studied, together with healthy controls (HC). Serum HLA-G levels were measured by enzyme-linked immunosorbent assay.

RESULTS

In TOL patients, monocytoid dendritic cell (mDC) but not plasmacytoid dendritic cell expressed higher HLA-G than in MI patients or HC. In TOL patients, the incidence of CD4(+)CD25(hi)CD127(-) regulatory T cells (Treg) and the intensity of Treg forkhead box p3 (Foxp3) expression were significantly higher than in the MI group. HLA-G expression on circulating mDC correlated significantly with that of Foxp3 in the TOL group. There was no correlation between immunosuppressive drug (tacrolimus) dose or trough level and HLA-G expression or Treg frequency or Foxp3 expression. The incidence of patients with circulating HLA-G levels more than 100 ng/mL was highest in the TOL group, although statistical significance was not achieved.

CONCLUSIONS

Higher HLA-G expression on circulating mDC in TOL recipients compared with MI or HC, suggests a possible role of HLA-G in immune regulation possibly mediated by enhanced host Treg Foxp3 expression.

Finding the right time for weaning off immunosuppression in solid organ transplant recipients

Solid organ transplantation (SOT) requires lifelong immunosuppression (IS) to prevent rejection and graft loss. The currently adopted immunosuppressive protocols are numerous and are based on the administration of at least two molecules with diverse mechanisms of action. Owing to the fact that the majority of immunosuppressants act non-selectively, the immune system is normally oversuppressed, and as a result is less able to both defend the host against infection and to control the spread of malignant cells. Consequently, long-term IS is burdened by chronic toxicity, which may be highly invalidating and may significantly influence patient's quality of life, compliance to treatment, overall success rate, and patient and graft survival. In an ideal scenario, SOT recipients should initially receive just enough IS to favor the onset of clinical operational tolerance (COT), a condition where the immune system of the host does not attack the graft in the absence of any immunosuppressant. COT has been documented after liver transplantation (LT) and renal transplantation (RT). First, COT was accidentally detected in patients who were nonadherent to treatment and who spontaneously decided to stop all IS without any medical guidance or surveillance. Later, it was described in recipients who required IS withdrawal following the occurrence of malignant diseases. Based on strikingly convincing experimental data, several tolerogenic protocols have recently been applied in patients but overall the results have been disappointing. The current literature demonstrates that COT can be safely achieved in stable LT recipients, with completely different strategies. Importantly, the onset of an episode of acute rejection during the attempt of IS withdrawal would not worsen the clinical outcome. On the contrary, COT remains a major challenge after RT because the onset of acute rejection will substantiate in graft loss. Currently, a major field of investigation aims to define markers of COT, which will allow the selection of individuals who are more prone to develop COT. Preliminary results in both RT and LT have just been announced; however, these markers will require validation in prospective studies.

Intratumoral neoadjuvant immunotherapy using IL-12 and dendritic cells is an effective strategy to control recurrence of murine hepatocellular carcinoma in immunosuppressed mice

Liver transplantation is accepted as an effective therapy for hepatocellular carcinoma (HCC). However, recurrence is one of the most fatal complications. The aim of this study is to evaluate the efficacy of intratumoral immunotherapy using IL-12 gene therapy and dendritic cell injection for the purpose of effective treatment for HCC under conditions of immunosuppression. We found that the combined immunotherapy significantly induced sustained and high amounts of intratumoral IL-12 and IFN-gamma proteins and that it induced high HCC-specific CTL activity under immunosuppression as compared with each monotherapy or control. The combined immunotherapy also exerted effective antitumor effects on the immunosuppressed host, resulting in significant suppression of growth of the s.c. established tumor and complete suppression of lung and liver metastasis, without rejection of a fully allogeneic skin graft. These antitumor effects were dependent on both T cells and NK cells. Noteworthily, the combined intratumoral immunotherapy and tumor resection (that is, neoadjuvant immunotherapy) resulted in achievement of tumor-free and long-term survival of the some immunosuppressed mice, even when the mice were challenged with i.v. injection of HCC at the time of tumor resection. In contrast, all of the mice treated with neoadjuvant immunotherapy using monotherapy or control therapy suffered from lung and liver metastasis. These results suggest that intratumoral neoadjuvant immunotherapy using IL-12 gene therapy and dendritic cell therapy is a potent effective strategy to control recurrence of HCC in patients after liver transplantation for HCC and may be applicable to general cancer treatment.

Identification of a B cell signature associated with renal transplant tolerance in humans

Establishing long-term allograft acceptance without the requirement for continuous immunosuppression, a condition known as allograft tolerance, is a highly desirable therapeutic goal in solid organ transplantation. Determining which recipients would benefit from withdrawal or minimization of immunosuppression would be greatly facilitated by biomarkers predictive of tolerance. In this study, we identified the largest reported cohort to our knowledge of tolerant renal transplant recipients, as defined by stable graft function and receiving no immunosuppression for more than 1 year, and compared their gene expression profiles and peripheral blood lymphocyte subsets with those of subjects with stable graft function who are receiving immunosuppressive drugs as well as healthy controls. In addition to being associated with clinical and phenotypic parameters, renal allograft tolerance was strongly associated with a B cell signature using several assays. Tolerant subjects showed increased expression of multiple B cell differentiation genes, and a set of just 3 of these genes distinguished tolerant from nontolerant recipients in a unique test set of samples. This B cell signature was associated with upregulation of CD20 mRNA in urine sediment cells and elevated numbers of peripheral blood naive and transitional B cells in tolerant participants compared with those receiving immunosuppression. These results point to a critical role for B cells in regulating alloimmunity and provide a candidate set of genes for wider-scale screening of renal transplant recipients.

Role of T cells in graft rejection and transplantation tolerance

Transplantation is the most effective treatment for end-stage organ failure, but organ survival is limited by immune rejection and the side effects of immunosuppressive regimens. T cells are central to the process of transplant rejection through allorecognition of foreign antigens leading to their activation, and the orchestration of an effector response that results in organ damage. Long-term transplant acceptance in the absence of immunosuppressive therapy remains the ultimate goal in the field of transplantation and many studies are exploring potential therapies. One promising cellular therapy is the use of regulatory T cells to induce a state of donor-specific tolerance to the transplant. This article first discusses the role of T cells in transplant rejection, with a focus on the mechanisms of allorecognition and the alloresponse. This is followed by a detailed review of the current progress in the field of regulatory T-cell therapy in transplantation and the translation of this therapy to the clinical setting.

Heterogeneous inflammatory changes in liver graft recipients with normal biochemistry

BACKGROUND

Patients with established liver grafts may receive excessive immune suppression. Liver biopsies were analyzed in those with normal liver biochemistry to identify parameters that might identify such cases.

METHODS

Patients with established grafts (>3 years from engraftment) and normal liver biochemistry (normal alanine transaminase, alkaline phosphatase, and bilirubin) were invited to undergo liver biopsy. Liver tissue was assessed by routine histopathology, a modified Ishak score, and immunohistochemistry for lymphocyte and cell-cycle markers. Circulating and intrahepatic lymphocytes were subjected to flow cytometry. Data were subjected to principal component analysis.

RESULTS

Two hundred twenty-five (40%) patients under regular review had an established graft with normal liver biochemistry; liver tissue was obtained in 55. Liver histology was normal in eight cases (14.5%). The most common abnormalities were mild nonspecific hepatitis in 25 (45.4%) and disease recurrence in 14 (25.4%). Principal component analysis identified a cluster of variables that accounted for a significant degree of variation within the dataset. These were lobular inflammation, portal inflammation, interface hepatitis, and fibrosis.

CONCLUSIONS

Inflammation persisted in established grafted livers in most patients with normal liver biochemistry. Systematic histological and lymphocyte phenotype analysis generated an index that distinguished patient groups. Those with least inflammation and the lowest alanine transaminase may have a reduced requirement for immune suppression.

Tolerance: is it achievable in pediatric solid organ transplantation?

In the clinical arena of transplantation, tolerance remains, for the most part, a concept rather than a reality. Although modern immunosuppression regimens have effectively handled acute rejection, nearly all organs except the liver commonly suffer chronic immunologic damage that impairs organ function, threatening patient and allograft survival. In addition to the imperfect control of the donor-directed immune response, there are additional costs. First, there is the burden of mortality from infection and malignancy that can be directly attributed to a crippled immune system. Second, there are insidious effects on renal function, cardiovascular profile (hypertension, hyperglycemia, and dyslipidemia), bone health, growth, psychological and neurocognitive development, and overall quality of life. It is likely that the full consequences of lifelong immunosuppression on our pediatric transplant recipients will not be fully appreciated until survival routinely extends beyond 1 or 2 decades after transplantation. Therefore, it can be argued that the holy grail of transplantation tolerance is of the utmost importance to children who undergo solid organ transplantation.

Distinct response of liver myeloid dendritic cells to endotoxin is mediated by IL-27

BACKGROUND/AIMS

The liver lies downstream of the gut, and is constantly exposed to bacteria. Liver dendritic cells (DC) are known to possess properties of tolerance, and respond to LPS differently when compared to conventional DC, but the underlying mechanisms are not completely understood. The aim of this study was to evaluate liver DC response to LPS stimulation.

METHODS

Liver or spleen derived DC were isoloated from mice treated with plasmid-GM-CSF hydrodynamic injection. The surface molecules and TLR4 expression on DC and cytokine productions of LPS stimulated DC were determinded by FACS analysis, ELISA and qPCR. The ability of DC to elicit T cell responses and differentiation were examined by MLR/CTL assay and qPCR for molecular markers related to Th1/Th2/Treg.

RESULTS

In this study, we demonstrated that the threshold of LPS stimulation for liver DC was markedly higher than spleen DC, even though the expression of TLR4 on both DCs was comparable. In contrast to spleen DC that produced high levels of IL-12 and induced Th1 response upon LPS stimulation, LPS-liver DC preferentially produced IL-10 and IL-27, instead of IL-12. In addition, liver DC induced T cell hyporesponsiveness, associated with selective expansion of CD4(+)Foxp3(+)T regulatory cells. Addition of exogenous IL-12 only slightly enhanced liver DC-induced T cell response. Interestingly, abrogation of IL-27 ligation by using IL-27R(-/-) T cells synergistically augmented the effect of IL-12, suggesting that IL-27 produced by liver DC plays a crucial role in induction of T cell hyporesponsiveness.

CONCLUSIONS

Liver DC respond distinctly to LPS stimulation by secreting IL-27 which synergizes with silencing of bioactive IL-12 activity leading to profound T cell inhibition.

Operational tolerance after liver transplantation

The achievement of an immunosuppression (IS)-free state after transplantation represents the ultimate goal of any immunosuppressive regimen. While clinical operational tolerance (COT) remains the exception after other types of solid organ transplantation, several cases of COT have been described after liver transplantation (LT). Overall, the experience gained so far worldwide demonstrates that COT can be achieved safely in one quarter of selected individuals, irrespective of the immunological background of donor and recipient, patient age, indication for LT, study endpoint, length of the weaning period and of pre/post-weaning follow-up, presence or not of chimerism. However, most transplant physicians still believe that the achievement of COT is still out of reach for the majority of LT recipients because of the potential risk for transplant survival, the non-randomized nature of most of the studies reported so far, and the selective nature of the patients enrolled in such studies, making them non-representative of the whole population of LT recipients. Despite these concerns, the present article demonstrates that this attitude is potentially no longer justified, given the growing evidence that a permanent and stable IS-free state can be achieved in a proportion of individuals who have received a LT for non-immune mediated liver diseases.

Requirement of protocol biopsy before and after complete cessation of immunosuppression after liver transplantation

BACKGROUND

Operational tolerance is defined as long-term acceptance of a transplanted organ after complete cessation of immunosuppression (IS), but may not always protect against antigen-dependent changes in graft morphology.

METHOD

IS free patients after living-donor liver transplantation (LDLT) underwent protocol biopsy (tolerance group [Gr-Tol]) and were evaluated for rejection and fibrosis. The degree of fibrosis was compared with those in the patients on maintenance IS group (Gr-IS) and the base line normal liver group (Gr-BS). When bridging fibrosis or progression of fibrosis was observed, IS was reintroduced or increased in Gr-Tol or in the patients in the weaning process.

RESULTS

Neither acute nor chronic rejection was observed. The degree of fibrosis, however, was significantly greater in Gr-Tol than those in Gr-IS and Gr-BS. In Gr-Tol, the number of graft infiltrating FOXP3 cells was significantly increased, the interval between LDLT and biopsy plus the donor age was significantly longer, and recipient age at LDLT was significantly younger, compared with those in Gr-IS. However, none of these three parameters correlated with the degree of fibrosis. In 7 of 11 patients in whom IS was reintroduced or increased, the improvement of fibrosis was observed by the subsequent biopsy.

CONCLUSION

Grafts of operationally tolerant patients after LDLT did not exhibit acute or chronic rejection, but they exhibited fibrosis. It remains elusive whether fibrosis observed in tolerant grafts is antigen dependent. The finding that after [corrected] the reintroduction or the increase of IS fibrosis was improved supported the possibility that fibrosis in operationally tolerant patients was antigen dependent.

Long-term management of immunosuppression after pediatric liver transplantation: is minimization or withdrawal desirable or possible or both?

PURPOSE OF REVIEW

The aim is to review available data regarding the risks and benefits of indefinite immunosuppression against attempted immunosuppression withdrawal for children who have undergone liver transplantation.

RECENT FINDINGS

Emerging data suggest that conventional immunosuppression practices may well be responsible for a substantial proportion of the long-term mortality and morbidity burden borne by pediatric liver transplant recipients. The cumulative risk of chronic kidney disease, infection, malignancy, and cardiovascular risk factors such as hypertension, diabetes, and hyperlipidemia appear to threaten the health and well being of children more than that of acute or chronic allograft rejection. In parallel, single-center experiences have suggested that gradual immunosuppression withdrawal can be done safely with higher success rates in pediatric compared with adult liver transplant recipients. The coalescence of these two data streams has engendered substantial interest in systematic exploration of the safety and efficacy of immunosuppression withdrawal in conjunction with a vigorous scientific effort to elucidate an immunologic signature predictive of successful withdrawal.

SUMMARY

There is a concerted effort within the transplant community to identify biomarkers that can accurately predict the success of immunosuppression withdrawal after liver transplantation. Freedom from lifelong immunosuppression is likely to yield considerable benefit, particularly for children who face the longest lifetime horizons.

Improving long-term outcomes after liver transplantation in children

The objective was to review the current state of knowledge and recommend future research directions related to long-term outcomes for pediatric liver transplant recipients. A 1-day Clinical Research Workshop on Improving Long-Term Outcomes for Pediatric Liver Transplant Recipients was held on February 12, 2007, in Washington, DC. The speaker topics were germane to research priorities delineated in the chapters on Pediatric Liver Diseases and on Liver Transplantation in the Trans-NIH Action Plan for Liver Disease Research. Issues that compromise long-term well-being and survival but are amenable to existing and new research efforts were presented and discussed. Areas of research that further enhanced the research priorities in the Action Plan for Liver Disease Research included collection of longitudinal data to define emerging trends of clinical challenges; identification of risk factors associated with long-term immunosuppression complications; development of tolerance-inducing regimens; definition of biomarkers that reflect the level of clinical immunosuppression; development of instruments for the measurement of health wellness; identification of risk factors that impede growth and intellectual development before and after liver transplantation and identification of barriers and facilitators that impact nonadherence and transition of care for adolescents.

The Tor Vergata weaning off immunosuppression protocol in stable HCV liver transplant patients: the updated follow up at 78 months

BACKGROUND

We report the update of the Tor Vergata immunosuppression (IS) weaning protocol in stable hepatitis C virus (HCV) liver transplant (LT) recipients.

METHODS

The weaning off IS was attempted in 34 patients who had received a LT 63.5+/-20.1 month earlier, for HCV-related end stage liver disease. Patients were observed over a period of 6.5 years. During this time, yearly protocol liver biopsies were performed. Primary endpoints were determined as the feasibility of weaning off IS and its impact on the long term disease progression. Secondary endpoints were defined as the impact on patient morbidity and quality of life.

RESULTS

Of the 8 originally tolerant patients, 7 remain alive and in good condition, while 1 died of severe HCV recurrence 10 years post-LT and 6 years after complete removal of IS. Four out of 26 intolerant individuals died of HCV recurrence (2x), lung carcinoma (1x) and acute myocardial infarction (1x), after a mean follow up period from LT of 115 (range 100-124). The 10-year survival from LT was comparable (89% vs. 87.5%). Liver graft pathology showed no significant differences between the two groups in terms of staging, fibrosis progression rate, and grading. Quantitative HCV RNA assay showed a significant non-logarithmic difference between the two groups (p = 0.03). The two groups were comparable in terms of liver function tests and lipid profile, whereas they differed with regards to glycaemia. While all tolerant individuals were euglicemic, 11 intolerant individuals developed new onset diabetes that required specific treatment (p = 0.03). Finally, significantly more intolerant patients are suffering from either cardiovascular (14/22 vs. 0/7, p = 0.01) or infectious diseases (13/22 vs. 0/7, p = 0.01).

CONCLUSIONS

After a 6.5-year follow up, the complete withdrawal of IS in HCV LT recipient remains safe and beneficial to patients, because it reduces the IS-related morbidity and increases the quality of life. The impact on HCV disease recurrence is less marked than after 3.5 years.

Monitoring of human liver and kidney allograft tolerance: a tissue/histopathology perspective

Several factors acting together have recently enabled clinicians to seriously consider whether chronic immunosuppression is needed in all solid organ allograft recipients. This has prompted a dozen or so centers throughout the world to prospectively wean immunosuppression from conventionally treated liver allograft recipients. The goal is to lessen the impact of chronic immunosuppression and empirically identify occasional recipients who show operational tolerance, defined as gross phenotype of tolerance in the presence of an immune response and/or immune deficit that has little or no significant clinical impact. Rare operationally tolerant kidney allograft recipients have also been identified, usually by single case reports, but only a couple of prospective weaning trials in conventionally treated kidney allograft recipients have been attempted and reported. Pre- and postweaning allograft biopsy monitoring of recipients adds a critical dimension to these trials, not only for patient safety but also for determining whether events in the allografts can contribute to a mechanistic understanding of allograft acceptance. The following is based on a literature review and personal experience regarding the practical and scientific aspects of biopsy monitoring of potential or actual operationally tolerant human liver and kidney allograft recipients where the goal, intended or attained, was complete withdrawal of immunosuppression.

Exhaustive differentiation of alloreactive CD8+ T cells: critical for determination of graft acceptance or rejection

BACKGROUND

The precise role that CD8+ T cells play in the rejection and acceptance of different types of allograft is unclear and has been shown to vary between donor-recipient combinations.

METHODS

The response of adoptively transferred CD8+ T cells reactive to the donor alloantigen H2Kb was examined after transplantation of H2Kb liver, kidney, and heart grafts in mice.

RESULTS

After transfer of 6 x 10(6) alloreactive CD8+ T cells to T-cell depleted syngeneic mice spontaneous long-term acceptance of liver grafts was observed, whereas kidney and heart grafts were acutely rejected. Within 5 days of liver transplantation, we found that the entire H2Kb-reactive T-cell pool was stimulated to proliferate and differentiate into memory or effector cells that were detectable within lymphoid tissues as well as the liver graft itself. However, despite the generation of effector or memory T cells, liver allografts were accepted, which correlated with the exhaustion or deletion of such cells. In contrast, although activation and proliferation of H2Kb-reactive CD8+ T cells was observed after transplantation of heart or kidney grafts, unactivated, H2Kb-reactive CD8+ T cells were still present in the spleen even long term. Interestingly, differences in the effector function of liver and kidney graft infiltrating donor-reactive CD8+ T cells were not detected after adoptive transfer into immunodeficient mice, despite a reduction in Th1-type cytokines within liver grafts.

CONCLUSIONS

The rapid and extensive initial activation and differentiation of donor-reactive CD8+ T cells that occurs after liver transplantation leads to clonal exhaustion or deletion of the alloreactive CD8+ T-cell repertoire resulting in spontaneous tolerance induction.

Protocol liver allograft biopsies

Protocol liver allograft biopsies are liver biopsies carried out at specific time points according to predetermined guidelines, rather than in response to specific indications such as change in the patient's clinical status or biochemical tests. Use of protocol liver allograft biopsy has been declining over the last decade: an informal survey of 35 transplant units showed that whereas 65% of units undertake protocol biopsies for those grafted for Hepatitis C virus infection, only 25% do so for patients grafted for other indications. In this overview, we consider the arguments against and those in favor of liver biopsies in adult liver allograft recipients. Arguments against the use of protocol liver biopsies are that they biopsies put the patient are associated with a small risk of morbidity and mortality, are expensive, do not provide useful information and do not alter clinical practice. The estimated rate of major complications is 0.6% and the estimated mortality rate 0.02%. However, the argument in favor of protocol biopsies is that even when standard liver tests are normal, there is on-going inflammation in the graft which, if immunosuppression is not altered, will lead to progressive fibrosis, cirrhosis and even graft loss. Conversely, normal liver histology may allow for reduction in the immunosuppression and so lower the risk of the complications associated with immunosuppression. Currently available diagnostic techniques are not yet sufficiently sensitive or specific to provide an accurate reflection of the state of the graft and the presence or absence of graft damage. We conclude that, while there are no clear data showing that protocol liver allograft biopsies are cost effective and lead to improved patient and graft outcome, such biopsies still have a role in the management of the liver transplant recipient.

Randomized controlled trial of total immunosuppression withdrawal in liver transplant recipients: role of ursodeoxycholic acid

BACKGROUND

Total immunosuppression withdrawal (TIW) without causing rejection has been reported in stable liver recipients. The role of ursodeoxycholic acid (UDCA) and patient characteristics that predict the success of this tolerance are unclear. There are two goals, to determine: 1) whether TIW is frequently associated with rejection; and 2) whether UDCA decreases the risk of liver disease (both rejection and recurrence) after TIW.

METHODS

Twenty-six liver recipients who had been free of rejection while on immunosuppressive agents for a minimum of 2 years were randomized to receive either (15 mg/kg) of UDCA (n=14) or identical placebo (n=12) followed by sequential withdrawal of their immunosuppressive regimen over several months. Endpoints were defined as biochemical and histological evidence of rejection, graft dysfunction without rejection, recurrence of pretransplant disease, or 6 months without immunosuppression and no rejection or dysfunction on repeat liver biopsy.

RESULTS

Rejection occurred in 6 of 14 (43%) of the UDCA group and 9 of 12 (75%) of those receiving placebo (P=0.09). Degree of rejection was mild, moderate, and severe in 73%, 20%, and 7% of patients respectively. All responded to rescue therapy and none developed chronic rejection. Nine of the remaining 11 patients (eight of the UDCA recipients and three of controls) who did not develop rejection developed graft dysfunction which responded to reintroduction of immunosuppressive agents in each case. Disease recurrence was most common in patients with underlying immune-mediated disorders of the liver. One year after withdrawal only two patients were free of immunosuppression, 80% were able to discontinue prednisone therapy (steroid free), and 50% were able to reduce their dose of cyclosporine. Age, underlying cause of liver disease, and regimen of immunosuppression were favorable predictors.

CONCLUSIONS

The results of this study suggest that TIW: 1) is frequently associated with subsequent rejection, 2) increases the risk of underlying disease recurrence, and 3) is not facilitated by UDCA use and responds properly to the reintroduction of immunosuppressive therapy.

CD25+CD4+ Regulatory T Cells Develop in Mice Not Only During Spontaneous Acceptance of Liver Allografts but Also After Acute Allograft Rejection

BACKGROUND

Liver grafts transplanted across a major histocompatibility barrier are accepted spontaneously and induce donor specific tolerance in some species. Here, we investigated whether liver allograft acceptance is characterized by, and depends upon, the presence of donor reactive CD25CD4 regulatory T cells.

METHODS

CD25 and CD25CD4 T cells, isolated from CBA. Ca (H2) recipients of C57BL/10 (B10; H2) liver and heart allografts 10 days after transplantation, were transferred into CBA. Rag1 mice to investigate their influence on skin allograft rejection mediated by CD45RBCD4 effector T Cells.

RESULTS

Fully allogeneic B10 liver allografts were spontaneously accepted by naive CBA.Ca recipient mice, whereas B10 cardiac allografts were acutely rejected (mean survival time=7 days). Strikingly, however, CD25CD4 T cells isolated from both liver and cardiac allograft recipients were able to prevent skin allograft rejection in this adoptive transfer model. Interestingly, CD25CD4 T cells isolated from liver graft recipients also showed suppressive potency upon adoptive transfer. Furthermore, depletion of CD25CD4 T cells in primary liver allograft recipients did not prevent the acceptance of a secondary donor-specific skin graft.

CONCLUSIONS

Our data provide evidence that the presence of CD25CD4 regulatory T cells is not a unique feature of allograft acceptance and is more likely the result of sustained exposure to donor alloantigens in vivo.

Liver immunity and tumour surveillance

Adult liver has a complex defence system that is critical in protection against infectious challenge. Its role in tumour surveillance is poorly understood. Because of its location, function and complex blood supply, the liver will be exposed to metastatic cells generated anywhere else in the body. Moreover, the role of the liver in detoxification can result in the generation of products with carcinogenic properties. It should not be surprising, then, to discover that the liver has a specialized immune system tailored to protect against and respond to significant immunological challenge, particularly metastasis and malignancy. This tumour surveillant role is the focus of this review.

Clinical tolerance following liver transplantation: long term results and future prospects

The ongoing quest of achieving clinical transplantation tolerance has been fueled, in large part, by the success of solid organ transplantation. Long term morbidity following transplantation now is primarily related to complications of immunosuppression (IS) such as malignancy, drug toxicity, or infection. This report provides long term follow-up on a large cohort of operationally tolerant patients, provides clinical guidelines to be considered in IS withdrawal, and identifies future prospects for achieving consistent clinical tolerance following liver transplantation (LT).

Skin Cancer After Transplantation: A Guide for the General Surgeon

The success of organ transplantation has been accompanied by serious concerns regarding the incidence and management of potentially catastrophic cutaneous carcinogenesis in transplant recipients. Delivery of the highest quality of care requires a concerted effort toward collaboration between multiple surgical and medical specialties. The purpose of this review is to provide the general surgeon with a practical, user-friendly guide to the important components of comprehensive dermatologic care for organ transplant recipients (OTRs) with references to more detailed sources of information.

Operational tolerance in clinical liver transplantation: emerging developments

There is still little understanding of the immune events that occur in transplant patients as they develop a relationship with their graft alloantigens. Though, there is an enormous interest and motivation in inducing specific unresponsiveness to organ allografts in order to allow minimization or complete withdrawal of immunosuppression in the recipient, given that life-long immunosuppressive treatment entails a high risk of infectious and metabolic complications, malignancies, and drug-specific toxicity. Clinical tolerance is defined as stable normal graft function in the total absence of a requirement for maintenance immunosuppression. Effective clinical tolerance has been reported more frequently in liver transplant recipients than after transplantation of other organs, as the liver is an immune-privileged organ for several mechanisms, most of which still remain unclear. According to the English medical literature, cautious, carefully supervised weaning of immunosuppressive drugs in controlled trials is not unreasonable, especially when monitored by protocol biopsies. The five centers in which the weaning has been attempted have reported a similar degree of success (1 out of 4 patients) and no harm to the patient over the short-term. Though, long-term follow-up has been lacking and, at present, there are no reliable immunological parameters that enable patients who can be withdrawn from immunosuppressants without the risk of rejection to be identified. To achieve that goal, appropriate collaboration and interaction between clinicians, immunologists and other basic scientists are desirable, as well as the creation of an international, maybe intercontinental, registry for tolerant patients.

Current issues in pediatric transplantation

Pediatric solid organ transplantation is so successful that >80% of children will survive to become teenagers and adults. Therefore, it is essential that these children maintain a good quality life, free of significant long-term side effects. While intensive immunosuppressive regimens (containing CsA, tacrolimus, MMF, and steroids) effectively reduce acute or chronic rejection, they can produce long-term side effects including viral infection, renal dysfunction, hypertension, and stunting. The development of effective methods of diagnosis, prevention, and treatment of CMV means that this is no longer a significant cause of mortality, but morbidity remains high. In contrast, infection rates of EBV remain high in EBV-negative pre-transplant patients. However, pre-emptive reduction of immunosuppression or treatment with rituximab or adoptive T-cell therapy is effective in preventing/treating post-transplant lymphoproliferative disease. Recent protocols have concentrated on reducing CsA immunosuppression, to prevent unacceptable cosmetic effects, and to reduce the hypertension, hyperlipidemia, and nephrotoxicity. Both CsA and tacrolimus cause a 30% reduction in renal function, with 4-5% of patients developing severe chronic renal failure. The use of IL-2 inhibitors for induction therapy with low-dose calcineurin inhibitors, in combination with renal-sparing drugs such as MMF or sirolimus for maintenance immunosuppression, should prevent significant renal dysfunction in the future. The concept of steroid-free immunosuppression with IL-2 inhibitors, tacrolimus, and MMF is an attractive option, which may reduce stunting and renal dysfunction. However, these regimens may be associated with the increased development of de-novo autoimmune hepatitis in 2-3% of children. The most important challenge to long-term survival in transplanted children is the management of non-adherence and other adolescent issues, particularly when transferring to adult units, as this is the time when many successful transplant survivors lose their grafts.

Complete weaning off immunosuppression in HCV liver transplant recipients is feasible and favourably impacts on the progression of disease recurrence

BACKGROUND/AIMS

HCV-related disease recurrence progresses rapidly after liver transplantation. We hypothesised that withdrawal of immunosuppression might favourably impact on disease progression.

METHODS

Weaning off immunosuppression was attempted in 34 HCV-RNA positive patients (mean age 62+/-6.4 years) transplanted 63.5+/-20.1 months earlier, under cyclosporine A monotherapy. Patients were followed for 3 years including yearly protocol liver biopsies. Primary endpoints were feasibility of weaning off immunosuppression and its impact on disease progression. Secondary endpoint was to identify predictors of an immunosuppression-free state and fibrosis progression.

RESULTS

Complete and permanent immunosuppression withdrawal was achieved in 8 patients (23.4%), whereas 14 (41.2%) developed rejection within eight months despite an initial response and 12 (35.2%) rejected during tapering. After a mean follow-up 45.5+/-5.8 months weaned patients showed stabilisation/improvement of histological fibrosis (P<0.01), lower necro-inflammation (P<0.02) and improved liver function (P<0.05) compared to weaning-intolerants. Multiple logistic regression identified low blood cyclosporine A trough levels during the first post-transplant week (P=0.004) and initial steroid-free immunosuppression (P<0.008) as independent predictors of sustained weaning. Achievement of immunosoppression freedom (P=0.02) and baseline staging score (P<0.0001) were independently associated with stabilisation/improvement of histological fibrosis.

CONCLUSIONS

Reconstitution of immune-competence in the host improves the natural history of HCV recurrence in the graft.

Low circulating regulatory T-cell levels after acute rejection in liver transplantation

Immune regulatory CD4+CD25+ T cells play a crucial role in inducing and maintaining allograft tolerance in experimental models of transplantation (Tx). In humans, the effect of Tx and immunosuppression on the function and homeostasis of CD4+CD25+ regulatory T cells (Tregs) is not well characterized. In this study, the frequency of Tregs in liver transplant recipients was determined based on flow cytometric analysis of CD4, CD25, CD45RO, and cytotoxic T lymphocyte antigen (CTLA)-4 markers, and the suppressor activity of Tregs was assessed in a mixed-leukocyte reaction. A link between Tregs, acute rejection, and immune-suppressive treatment was investigated. Liver transplant recipients had significantly higher Treg levels in peripheral blood pre-Tx than healthy controls. After Tx, a significant drop in the Treg fraction was observed. This reduction of circulating Tregs was transient and was associated with immunosuppression. In recipients who did not develop rejection, a relative recovery of Treg levels was seen within the first year after Tx. Recipients who experienced an episode of steroid-treated acute rejection, however, had sustained low Treg levels. The suppressive activities of CD4+CD25+ Tregs from rejectors, nonrejectors, and healthy controls on proliferation and interferon (IFN)-gamma production were indistinguishable. In conclusion, the percentage of CD4+CD25+CD45RO+CTLA-4+ quadruple-positive Tregs in peripheral blood decreases significantly after liver Tx. Treatment with methylprednisolone during Tx and for acute rejection is associated with low circulating Tregs. Despite these quantitative differences between rejectors and nonrejectors, the suppressive quality of CD4+CD25+ Tregs is identical in both groups.

The relative effects of different systemic immunosuppressives on skin cancer development in organ transplant patients

The immunosuppressive medications used in organ transplant recipients (OTRs) to prevent allograft rejection are associated with an increased incidence of skin cancer in this population. Several classes of immunosuppressive agents exist, and the selection of which medication to use varies by organ type and with time. The tumorigenic potential and relative effects of different immunosuppressive medications on skin cancer risk have been studied. This article reviewed the history of the immunosuppressive agents and their mechanisms of action. A summary of the current literature on the relationship between skin cancer and the different immunosuppressives were included. Guidelines for management of OTRs in dermatologic practice were discussed.

A technique of bone marrow collection from vertebral bodies of cynomolgus macaques for transplant studies

BACKGROUND

Strategies to induce donor-specific allograft tolerance are best tested in preclinical models developed in nonhuman primates (NHPs). Most protocols prepare the recipient by infusing hematopoietic cells from the donor. We report here a procedure to isolate and characterize large numbers of bone marrow cells (BMCs) from cynomolgus monkeys (cynos) that can then successfully be transplanted into conditioned recipients.

MATERIALS AND METHODS

Vertebral columns of five cynos were excised en bloc and separated into individual vertebrae. The cancelous bone was extracted with a core puncher, fractionated, filtered, centrifuged, and resuspended in transplantation media before being analyzed by flow cytometry. In two instances, the collected BMCs were reinfused into allogeneic recipients preconditioned with a nonmyeloablative regimen. Chimerism was monitored using short-tandem repeat analysis.

RESULTS

The mean total BMCs yield was 25.5 x 10(9) (range of 4.00 x 10(9) to 59 x 10(9)) with mean cell viability of 93.4% (range: 90-96%). CD34+ cells and CD3+ cells averaged 0.34 and 3.91% of total BMCs, respectively. This resulted in absolute cell number yields of 1.02 x 10(8) and 1.15 x 10(9) for CD34+ and CD3+ cells, respectively. Graft-versus-host disease was absent in both bone marrow infused animals, and a maximum level of chimerism of 18% was detected at 3 weeks after BMCs infusion.

CONCLUSION

We present here the first detailed report of a procedure to retrieve and characterize large numbers of BMCs from vertebral bodies of cynos and demonstrate that cells collected with this technique have the capability of engrafting in allogenic recipients.

The role of donor bone marrow infusions in withdrawal of immunosuppression in adult liver allotransplantation

We investigated the role of donor bone marrow cell (DBMC) infusions in immunosuppression withdrawal in adult liver transplantation. Patients enrolled were at least 3 years post-transplantation, with stable graft function. Forty-five (study group: G1) received DBMC, and 59 (control group: G2) did not. Immunosuppression was reduced by one third upon enrollment, by another third the second year of the study and was completely withdrawn the third year. Patient and graft survival were similar between the two groups. Although rejection episodes were significantly less in G1 the first 2 years of the study (35% vs. 57%, p = 0.016), there was no significant difference overall (74% vs. 81%, p = 0.14). Until February 2004, 20 patients, 10 in each group, were immunosuppression free for 1-3 years. Approximately 20% of long-term survivors of liver transplantation can successfully discontinue their immunosuppression. DBMC infusions, do not increase this likelihood.

Establishment of a new pig model for auxiliary partial orthotopic liver transplantation

AIM

To establish a new pig model for auxiliary partial orthotopic liver transplantation (APOLT).

METHODS

The liver of the donor was removed from its body. The left lobe of the liver was resected in vivo and the right lobe was used as a graft. After the left lateral lobe of the recipient was resected, end-to-side anastomoses of suprahepatic inferior vena cava and portal vein were performed between the donor and recipient livers, respectively. End-to-end anastomoses were made between hepatic artery of graft and splenic artery of the host. Outside drainage was placed in donor common bile duct.

RESULTS

Models of APOLT were established in 5 pigs with a success rate of 80%. Color ultrasound examination showed an increase of blood flow of graft on 5(th) d compared to the first day after operation. When animals were killed on the 5(th) d after operation, thrombosis of hepatic vein (HV) and portal vein (PV) were not found. Histopathological examination of liver samples revealed evidence of damage with mild steatosis and sporadic necrotic hepatocytes and focal hepatic lobules structure disorganized in graft. Infiltration of inflammatory cells was mild in portal or central vein area. Hematologic laboratory values and blood chemical findings revealed that compared with group A (before transplantation), mean arterial pressure (MAP), central venous pressure (CVP), buffer base (BB), standard bicarbonate (SB) and K(+) in group B (after portal vein was clamped) decreased (P<0.01). After reperfusion of the graft, MAP, CVP and K(+) restored gradually.

CONCLUSION

Significant decrease of congestion in portal vein and shortened blocking time were obtained because of the application of in vitro veno-venous bypass during complete vascular clamping. This new procedure, with such advantages as simple vessel processing, quality anastomosis, less postoperative hemorrhage and higher success rate, effectively prevents ischemia reperfusion injury of the host liver and deserves to be spread.

Inhibition of T-cell responses by hepatic stellate cells via B7-H1-mediated T-cell apoptosis in mice

In the injured liver, hepatic stellate cells (HSCs) secrete many different cytokines, recruit lymphocytes, and thus participate actively in the pathogenesis of liver disease. Little is known of the role of HSCs in immune responses. In this study, HSCs isolated from C57BL/10 (H2b) mice were found to express scant key surface molecules in the quiescent stage. Activated HSCs express major histocompatibility complex class I, costimulatory molecules, and produce a variety of cytokines. Stimulation by interferon gamma (IFN-gamma) or activated T cells enhanced expression of these molecules. Interestingly, addition of the activated (but not quiescent) HSCs suppressed thymidine uptake by T cells that were stimulated by alloantigens or by anti-CD3-mediated T-cell receptor ligation in a dose-dependent manner. High cytokine production by the T cells suggests that the inhibition was probably not a result of suppression of their activation. T-cell division was also found to be normal in a CFSE dilution assay. The HSC-induced T-cell hyporesponsiveness was associated with enhanced T-cell apoptosis. Activation of HSCs was associated with markedly enhanced expression of B7-H1. Blockade of B7-H1/PD-1 ligation significantly reduced HSC immunomodulatory activity, suggesting an important role of B7-H1. In conclusion, the bidirectional interactions between HSCs and immune cells may contribute to hepatic immune tolerance.

Living donor liver transplant with clinical tolerance, laboratory evidence of chimerism, and spontaneous clearance of HBV

We present a case of functional and histopathologic tolerance, chimerism, and spontaneous clearance of HBV in a patient four years after living donor liver transplant (LDLT). A 19-year-old male patient underwent a LDLT for HBV cirrhosis. He voluntarily ceased immunosuppression and antiviral therapy after 6 months. He is now four years status post transplant without any episodes of rejection or clinical manifestation of liver disease. PCR and VNTR were used to show donor-recipient chimerism and a large degree of genetic similarity between the pair. MLC and cytokine elaboration were used to show recipient hyporeactivity towards donor antigen. He also has clinical evidence of clearing his HBV without continued use of HBIG.

Guidelines for the management of squamous cell carcinoma in organ transplant recipients

BACKGROUND

Solid-organ transplant recipients have a high incidence of cutaneous squamous cell carcinoma (SCC) and often develop multiple and aggressive tumors. There are few published studies or reviews, which provide guidance to the clinician in the treatment of these patients.

OBJECTIVE

The objective was to develop useful clinical guidelines for the treatment of skin cancer in organ transplant recipients (OTRs).

METHODS

The members of the Guidelines Committee of the International Transplant-Skin Cancer Collaborative (ITSCC) carried out a computerized search utilizing the databases of the National Library of Medicine for reports in the literature on SCC in OTRs. These reports were collectively examined by the group and combined with experiences from the members' clinical practices in the development of the guidelines.

RESULTS

More than 300 articles relating to SCC in OTRs were reviewed. In general, reports concerning the prevention and treatment of SCC in OTRs are of individual cases or small case series. They are retrospective in nature, statistically nonrigorous, and lack the complete epidemiologic data necessary to derive definitive conclusions. Combining these studies and collective clinical experience, however, is at present the best available method for devising guidelines for the treatment of SCC in OTRs.

CONCLUSION

Guidelines developed for the treatment of skin cancer in OTRs, supported by the best available data and collective clinical experience, may assist in the management of OTRs with SCC. The development of clinical pathways and complete documentation with rigorous prospective study is necessary to improve and refine future guideline development.

Lessons of organ-induced tolerance learned from historical clinical experience1

Although the reductionist approach has served science well for 400 years, the accumulation of details can obscure the truth if the original premise is incorrect. One such premise has been that successful organ transplantation and bone marrow engraftment are fundamentally different outcomes involving separate and distinct mechanisms. Some historical clinical observations pointed to a different conclusion almost from the beginning and included clues about how to induce tolerance with the aid of immunosuppression.

Nontumoral dermatologic problems after liver transplantation

The skin, easily accessible for medical examination, is affected in many ways by liver transplantation. Mucocutaneous manifestations of advanced liver disease and dermatologic conditions associated with specific hepatic diagnoses generally improve after liver transplantation. Vasculitic lesions due to cryoglobulinemia associated with hepatitis C, and photosensitivity due to porphyria are occasional exceptions. Dermatologic diseases complicating the posttransplantation course can be challenging. Their presentation is sometimes unusual and their course severe. Infections with rare organisms alone or in combination may occur. Our intent is to provide an overview of the current knowledge regarding nontumoral dermatologic problems associated with liver transplantation by summarizing the available information from all documented case reports.

Strategies for optimizing immunosuppression in adolescent transplant recipients: a focus on liver transplantation

Adolescence is a difficult time for transplant recipients; they must learn to take responsibility for their own behavior and medication, and to balance their developing sexuality in a body that has been transformed by the adverse effects of immunosuppression. More than 80% of children survive transplantation to adolescence and adulthood, thus long-term outcome and tailoring of immunosuppression is of great importance. To date, the most experience with long-term immunosuppression regimens is cyclosporine, which is well tolerated and effective. Long-term adverse effects include hypertension, nephrotoxicity, and post-transplant lymphoproliferative disease (PTLD). The recent development of tacrolimus has improved the cosmetic adverse effects related to cyclosporine, but has similar rates of hypertension and nephrotoxicity, and possibly a higher rate of PTLD. There has been a recent, welcome development in renal sparing drugs, such as mycophenolate mofetil, which has no cosmetic adverse effects, does not require drug level monitoring and is thus particularly attractive to teenagers. Recent surveys demonstrate recovery of renal function with mycophenolate mofetil, if started prior to irreversible renal dysfunction. There are currently little published data on the use of sirolimus (rapamycin) in the pediatric population, but preliminary studies suggest that the future use of interleukin-2 receptor antibodies may be beneficial for immediate post-transplant induction of immunosuppression. It is important when planning immunosuppression for adolescents to consider the effects of drug therapy on both males and females in order to maintain fertility and to ensure safety in pregnancy. Noncompliance is a problem in this age group, but adequate practical measures and support should reduce noncompliance, and allow good, long-term graft function.

Liver tolerance mediated by antigen presenting cells: fact or fiction?

Possible mechanisms by which liver antigen presenting cells (APC) may facilitate tolerance induction are discussed. Tolerance may be facilitated by a distinctive combination of factors, linked to the unique anatomical and microenvironmental features of the liver.

Clinical trials of transplant tolerance: slow but steady progress

The search for tolerance therapies that would thwart the alloimmune response following organ transplantation while preserving a patient's protective immune response has been a formidable goal for clinical immunologists. Over the past few decades, a more detailed understanding of the molecular events associated with T-cell recognition and activation has demonstrated the feasibility of various tolerance approaches, such as costimulation blockade, in numerous animal models of both autoimmunity and transplantation. Yet, only a few promising new therapies have reached the early stages of human clinical development. In contrast, the use of T-cell depleting induction therapy has become widespread, and new trials have been designed with immunosuppressive drug withdrawal in mind. Furthermore, nonmyeloablative mixed chimeric approaches have allowed complete immunosuppressive withdrawal in some limited cases. In the course of these investigations, however, what has become increasingly clear is that the distinctions between immunosuppression and tolerance have been blurred as the success and durability of the therapies rely as much on the state of the organ and organism as they do the mechanism of action of the drug. In this review, we provide a summary of the progress and lessons in promoting clinical transplant tolerance and an overview of promising agents.

Dendritic cell subset ratio in peripheral blood correlates with successful withdrawal of immunosuppression in liver transplant patients

Human dendritic cell (DC) subsets appear to play distinct roles in the induction and regulation of immune responses. While monocytoid DC (DC1) induce T-helper (Th) 1-type responses, plasmacytoid DC (DC2) have been reported to selectively induce Th2 responses. In blood, their precursors (p) can be identified as HLA-DR+ lineage- cells that are further characterized as CD11c+ CD123-/lo (IL-3Ralpha-/lo) (pDC1) or as CD11c- CD123hi (pDC2) by rare event, flow cytometric analysis. We compared the incidences of pDC1 and pDC2 in peripheral blood mononuclear cell populations isolated from normal healthy controls and from 3 groups of clinically stable liver transplant patients. Group A had been successfully withdrawn from immunosuppression, whereas group B were undergoing prospective drug weaning and on minimal anti-rejection therapy. In group C, drug withdrawal had either failed or never been attempted and patients were on maintenance immunosuppression. Assessment of DC subsets and the pDC2 : pDC1 ratio showed good intra-and interassay reproducibility. Compared with patients in group C, those in groups A and B demonstrated a significantly higher relative incidence of pDC2 and a lower incidence of pDC1 - similar to those values observed in normal healthy controls. Moreover, the pDC2 : pDC1 ratio was significantly higher in patients undergoing (successful) weaning and in those off immunosuppression compared with patients on maintenance immunosuppression.

Correlation between daily cyclosporine dose and allograft injury in liver recipients with and without recurrent hepatitis C

BACKGROUND: After liver transplantation, the daily cyclosporine dose is adjusted to maintain the blood level in a chosen range. The aim of this study was to assess the influence of liver graft injury on cyclosporine dose. METHODS: The parameters of liver function were investigated in 145 patients. Ninety-two patients took part in a longitudinal study. RESULTS: The cyclosporine dose correlated with the MEGX test (r=0.38, P=0.01) and with the ICG (r=0.38, P=0.0001) and BSP (r=0.37, P=0.0002) clearances; it had an inverse correlation with transaminases (AST: r=0.38, P=0.0001) and histological lesions (r=-0.29, P=0.005). The cyclosporine dose was lower in patients with recurrent hepatitis C (179+/-9 mg/day) than in those without (241+/-10 mg/day), and was lower in patients with chronic hepatitis (154+/-9 mg/day) than in those without (207+/-16 mg/day). In the longitudinal study, the percent variation of AST correlated inversely with that of cyclosporine dose (r=-0.62, P=0.0002). CONCLUSION: Progressive graft injury leads to a reduction in the cyclosporine dose, particularly in patients with recurrent hepatitis C.