A short course of methylprednisolone immunosuppression inhibits both rejection and spontaneous acceptance of rat liver allografts

Evaluation of immunosuppression protocols for MHC-matched allogeneic iPS cell-based transplantation using a mouse skin transplantation model

BACKGROUND

Off-the-shelf major histocompatibility complex (MHC)-matched iPS cells (iPSC) can potentially initiate host immune responses because of the existence of numerous minor antigens. To suppress allo-immune responses, combination of immunosuppressants is usually used, but its efficacy to the allogeneic iPSC-based transplantation has not been precisely evaluated.

METHODS

Three transplantation models were used in this study; MHC-matched, minor antigen-mismatched mouse skin or iPSC-graft transplantation, and fully allogeneic human iPSC-derived liver organoid transplantation in immune-humanized mice. The recipients were treated with triple drugs combination (TDC; tacrolimus, methylprednisolone, and mycophenolate mofetil) or co-stimulatory molecule blockade (CB) therapy with some modifications. Graft survival as well as anti-donor T and B cell responses was analyzed.

RESULTS

In the mouse skin transplantation model, immunological rejection caused by the minor antigen-mismatch ranged from mild to severe according to the donor-recipient combination. The TDC treatment could apparently control the mild skin graft rejection when combined with a transient T cell depletion, but unexpected anti-donor T or B cell response was observed. On the other hand, CB therapy, particularly when combined with rapamycin treatment, was capable of attenuating both mild and severe skin graft rejection and allowing them to survive long-term without any unfavorable anti-donor immune responses. The efficacy of the CB therapy was confirmed in both mouse and human iPSC-derived graft transplantation.

CONCLUSIONS

The findings suggest that the CB-based treatment seems suitable to well manage the MHC-matched allogeneic iPSC-based transplantation. The TDC-based treatment may be also used to suppress the rejection, but screening of its severity prior to the transplantation seems to be needed.

Isolated Liver Rejection After Lung and Combined Kidney-Liver Transplantation: A Case Report

Liver allografts are unique in solid organ transplantation as they are less susceptible to both acute and chronic rejection. Operational tolerance, defined as prolonged graft survival in the absence of immunosuppression, is also achieved more frequently with liver allografts. It is unknown if the presence of multiple allografts in the same individual, levels of immunosuppression, or the presence of cystic fibrosis (CF) impacts the livers ability to ward off rejection or achieve operational tolerance. We describe an unsensitized, ABO-compatible patient with CF who underwent double lung transplantation and several years later a combined liver-kidney transplant. He developed isolated late acute T-cell mediated rejection of his liver allograft despite a high level of immunosuppression (IS) required for his lung and kidney allografts. To our knowledge, this is the first case of isolated liver rejection in a patient with 3 separate organ allografts, or in a patient with CF, to be reported in the literature. This isolated liver rejection is out of keeping with typically accepted ideas about orthotopic liver tolerance.

The Leuven Immunomodulatory Protocol Promotes T-Regulatory Cells and Substantially Prolongs Survival After First Intestinal Transplantation

Intestinal transplantation (ITx) remains challenged by frequent/severe rejections and immunosuppression-related complications (infections/malignancies/drug toxicity). We developed the Leuven Immunomodulatory Protocol (LIP) in the lab and translated it to the clinics. LIP consists of experimentally proven maneuvers, destined to promote T-regulatory (Tregs)-dependent graft-protective mechanisms: donor-specific blood transfusion (DSBT); avoiding high-dose steroids/calcineurin-inhibitors; and minimizing reperfusion injury and endotoxin translocation. LIP was tested in 13 consecutive ITx from deceased donors (2000-2014) (observational cohort study). Recipient age was 37 years (2.8-57 years). Five-year graft/patient survival was 92%. One patient died at 9 months due to aspergillosis, another at 12 years due to nonsteroidal anti-inflammatory drug-induced enteropathy. Early acute rejection (AR) developed in two (15%); late AR in three (23%); all were reversible. No chronic rejection (CR) occurred. No malignancies developed and estimated glomerular filtration rate remained stable post-Tx. At last follow-up (3.5 years [0.5-12.5 years]), no donor-specific antibodies were detected and 11 survivors were total parenteral nutrition free with a Karnofsky score >90% in 8 recipients (follow-up >1 years). A high frequency of circulating CD4⁺ CD45RA^- Foxp3^hi memory Tregs was found (1.8% [1.39-2.21]), comparable to tolerant kidney transplant (KTx) recipients and superior to stable immunosuppression (IS)-KTx, KTx with CR, and healthy volunteers. In this ITx cohort we show that DSBT in a low-inflammatory/pro-regulatory environment activates Tregs at levels similar to tolerant-KTx, without causing sensitization. LIP limits rejection under reduced IS and thereby prolongs long-term survival to an extent not previously attained after ITx.

Is minimal, [almost] steroid-free immunosuppression a safe approach in adult liver transplantation? Long-term outcome of a prospective, double blind, placebo-controlled, randomized, investigator-driven study

OBJECTIVE

To investigate the safety of minimal immunosuppression (IS) in liver transplantation (LT).

BACKGROUND

The lack of long-term follow-up studies, including pathologic data, has led to a protean handling of IS in LT.

METHODS

Between February 2000 and September 2004, 156 adults were enrolled in a prospective, randomized, double-blind, placebo-controlled minimization trial comparing tacrolimus placebo (TAC-PLAC) and TAC short-term steroid (TAC-STER) IS. All patients had a minimum clinical, biochemical, and histological follow-up of 5 years.

RESULTS

Five-year actual patient and graft survival rates in TAC-PLAC and TAC-STER groups were 78.1% and 82.1% (P=0.89) and 74.2% and 76.9% (P=0.90), respectively. Five-year biopsies were available in 112 (89.6%) of 125 survivors. Twelve patients refused a biopsy because of their excellent evolution; tissue material was insufficient in 1 patient; 11 had normal liver tests; and 2 patients had developed alcoholic and secondary biliary cirrhosis. Histology was normal in 44 (39.3%) patients; 35 (31.3%) had disease recurrence. The remaining biopsies showed nonspecific chronic hepatitis (14.3%), mild inflammatory infiltrates (10.7%), and steatosis (3.5%). All findings were equally distributed between both groups. In each group, 3 patients (4.8%) presented with acute cellular rejection after the first year and only 1 (0.9%) TAC-PLAC patient developed chronic rejection after IS withdrawal because of pneumonitis. Arterial hypertension, diabetes mellitus, renal insufficiency, hypercholesterolemia, gout, and obesity were equally low in both groups.

CONCLUSIONS

Excellent long-term results can be obtained under minimal IS and absence of steroids. TAC-based monotherapy is feasible in most adult liver recipients until 5 years of follow-up.

Prope tolerance after pediatric liver transplantation

pT, under mono- and infratherapeutic calcineurin inhibition, may constitute an optimal condition combining graft acceptance with low IS load and minimal IS-related toxicity. We reviewed 171 pediatric (<15.0 yr) survivors beyond one yr after LT, transplanted between April 1999 and June 2007 under tacrolimus-based regimens (median follow-up post-LT: 6.0 yr, range: 0.8-9.5 yr). Their current status regarding IS therapy was analyzed and correlated with initial immunoprophylaxis. pT was defined as tacrolimus monotherapy, with mean trough blood levels <4 ng/mL during the preceding year of follow-up, combined with normal liver function tests. The 66 children transplanted before April 2001 received a standard tacrolimus-steroid regimen. Beyond April 2001, 105 patients received steroid-free tacrolimus-basiliximab or tacrolimus-daclizumab immunoprophylaxis. In the latter group, 43 (41%) never experienced any acute rejection episode and never received steroids. In the long term, a total of 79 recipients (47%) developed pT (n = 73) or IS-free operational tolerance (n = 6), 27 of them belonging to the 43 steroid-free patients (63%). In contrast, only 52/128 (41%) children treated with steroids subsequently developed prope/operational tolerance (p = 0.012). Steroid-free tacrolimus-based IS seems to promote long-term graft acceptance under minimal/no IS. These results constitute the first evidence that minimization of IS, including steroid avoidance, might be tolerogenic in the long term after pediatric LT.

Immunosuppression induction with rabbit anti-thymocyte globulin with or without rituximab in 1000 liver transplant patients with long-term follow-up

Rabbit anti-thymocyte globulin (rATG)-based immunosuppression induction is being increasingly used in liver transplantation (LT) in conjunction with steroid-free protocols to delay the initiation of calcineurin inhibitors. This study reports a single-center comparison of transplant outcomes and complications in 3 immunosuppression eras. Data were obtained retrospectively from a center research database, and the analysis included LT patients from 2001 to 2008. The immunosuppression consisted of rATG induction in 3 doses (6 mg/kg in all): (1) the first dose was administered perioperatively [the rabbit anti-thymocyte globulin in the operating room (rATG-OR) era]; (2) the first dose was delayed until 48 hours after transplantation [the rabbit anti-thymocyte globulin after a delay (rATG-D) era]; or (3) the first dose was delayed until 48 hours after transplantation, and a single dose of rituximab was added 72 hours after transplantation [the rabbit anti-thymocyte globulin after a delay plus rituximab (rATG-D-Ritux) era]. The initial maintenance immunosuppression was tacrolimus monotherapy, which was started on postoperative day 2. There were 166 patients (16%) in the rATG-OR era, 259 patients (26%) in the rATG-D era, and 588 patients (58%) in the rATG-D-Ritux era (1013 patients in all). Demographically, the latter eras were characterized by higher recipient and donor ages; greater percentages of liver-kidney transplants, hepatocellular carcinoma (HCC), donation after cardiac death (DCD), and imported organs; and shorter graft ischemia times. There were no significant differences between the 3 immunosuppression groups in unadjusted patient survival 3 and 5 years after transplantation (80% and 75% for the rATG-OR era, 75% and 67% for the rATG-D era, and 79% and 71% for the rATG-D-Ritux era, P = 0.15). The 5-year survival rates for patients with hepatitis C virus (HCV) and HCC were 65% and 68%, respectively. The factors included in the Cox regression model for patient death included the Model for End-Stage Liver Disease score [hazard ratio (HR) = 1.03, P = 0.001], HCV (HR = 1.28, P = 0.04), donor age (HR = 1.01, P = 0.001), recipient age (HR = 1.01, P = 0.05), and DCD (HR = 1.55, P = 0.11). rATG-based induction immunosuppression can be safely used in adult LT recipients with excellent survival and low rejection rates and without increases in immunosuppression-related side effects.

Tolerance in liver transplantation

Operational tolerance (OT) in liver transplant patients occurs much more frequently than OT of other transplanted organs; however the rate of OT varies considerably with the centre and patient population. Rates of OT range from 15% of the total liver transplant (LTX) patient population down to less than 5%. This review examines the reports of liver OT and compares the factors that could contribute to this variation. Multiple factors were examined, including the time from transplantation when weaning of immunosuppression (IS) was commenced, the rapidity of weaning, the contribution of maintenance and induction IS and the patient population transplanted. The approaches that might be used to increase the likelihood of OT are discussed and the approaches to monitoring OT in LTX patients are reviewed.

Strategies to prevent cellular rejection in pediatric heart transplant recipients

Despite more than 40 years' experience in pediatric heart transplantation, cellular rejection remains a significant cause of morbidity and mortality. In this review, strategies and agents to prevent acute cellular rejection are discussed. Strategies to prevent rejection are divided into two phases - induction and maintenance therapies. Currently, the most commonly used induction agents are polyclonal antibodies (rabbit or equine antithymocyte globulin) and interleukin-2 receptor antibodies (daclizumab or basiliximab). Induction therapies have reduced early rejection, are renal sparing, and can reduce corticosteroid exposure, but have not yet been shown to have a longer term survival benefit. Multiple maintenance immunosuppressants are available. Nearly all regimens include a calcineurin inhibitor (either ciclosporin [cyclosporine] or tacrolimus). Most combinations in pediatric heart transplantation include an antiproliferative agent (azathioprine, mycophenolate mofetil or, less commonly, sirolimus). Everolimus has seen increasing use in adult heart transplant patients in Europe but, to date, its use is rare in pediatric heart transplantation. The use of corticosteroids as a third agent is still common, but strategies to avoid or minimize their use are increasing. The 'best' combination of therapies varies between studies. By gaining a better understanding of individuals' genetic and environmental risk factors, we may in the future be able to better predict the course of cardiac allografts and enhance our ability to tailor immunosuppression to individual patient variables with the ultimate goal of inducing a state of immune tolerance.

Once daily calcineurin inhibitor monotherapy in pediatric liver transplantation

This report describes a group of pediatric liver transplant recipients who have undergone once daily calcineurin inhibitor (CNI) monotherapy at Children's Memorial Hospital, Chicago, between January 1, 2001 and November 30, 2008. We defined success as normal liver enzymes at 1 year after dose change, with normal enzymes throughout all follow-up. Patients who did not meet the set criteria or had lost an organ to chronic rejection were not considered for this therapeutic strategy. There were 147 patients in our organ transplant tracking record (OTTR) who were > or = 5 years post liver transplant. Of these, 56 underwent reduced dose, once daily CNI monotherapy. Patients who met the set criteria were placed on once daily calcineurin inhibitor at half their previous dose. Fifty patients successfully achieved this dose change, while six patients failed at a mean of 3.7 +/- 3.2 months following the dosing change. The mean interval from transplant was significantly longer in those patients who were successful compared to those who failed dose change (p < 0.05). Importantly, there have been no graft losses. Reduced dose, once daily CNI monotherapy is safe in carefully selected recipients, with a longer interval post liver transplantation increasing the likelihood of success.

Noninvasive evaluation of immunosuppressive drug efficacy on acute donor cell survival

PURPOSE

The therapeutic benefits of cell transplantation may depend on the survival of sufficient numbers of grafted cells. We evaluate four potent immunosuppressive medications aimed at preventing acute donor cell death.

PROCEDURES AND RESULTS

Embryonic rat H9c2 myoblasts were stably transduced to express firefly luciferase reporter gene (H9c2-Fluc). H9c2-Fluc cells (3x10(6)) were injected into thigh muscles of Sprague-Dawley rats (N=30) treated with cyclosporine, dexamethasone, mycophenolate mofetil, tacrolimus, or saline from day -3 to day +14. Longitudinal optical bioluminescence imaging was performed over two weeks. Fluc activity was 40.0+/-12.1% (dexamethasone), 30.5+/-12.5% (tacrolimus), and 21.5+/-3.5% (mycophenolate) vs. 12.0+/-5.0% (control) and 8.3+/-5.0% (cyclosporine) at day 4 (P<0.05). However, by day 14, cell signals had decreased drastically to <10% for all groups despite drug therapy.

CONCLUSION

This study demonstrates the ability of optical molecular imaging for tracking cell survival noninvasively and raises important questions with regard to the overall efficacy of immunosuppressives for prolonging transplanted cell survival.

Minimization of steroids in liver transplantation

Because of the markedly improved short-term results of liver transplantation (LT) and persistently high number of long-term complications, the attention of transplant physicians should be focused on minimizing immunosuppressive therapy as much as possible. Steroid-based immunosuppression is responsible for a substantial post-LT morbidity and mortality, hence, minimization of its use is of utmost importance to improve the quality of life of the successfully transplanted liver recipient. This literature review shows that LT can be performed safely with steroid-minimal immunosuppression without compromising graft and patient survival. The tendency in clinical practice is to move more and more from steroid withdrawal to steroid avoidance protocols.

Tacrolimus monotherapy in liver transplantation: one-year results of a prospective, randomized, double-blind, placebo-controlled study

BACKGROUND

Minimal immunosuppression (IS) is desirable in organ transplantation to reduce side effects and to promote the process of tolerance induction.

MATERIAL AND METHODS

Between February 2000 and September 2004, 156 adults (>15 years old) receiving a primary liver graft were enrolled in a prospective, randomized, double-blind, placebo-controlled, investigator-driven single-center study comparing tacrolimus (TAC)-placebo (PL) and TAC-low-dose, short-term (64 days) steroid (ST) IS. There were no exclusion criteria at moment of randomization. All patients had a 12-month follow-up (range, 12-84).

RESULTS

Three- and 12-month patient survival rates were 93.6% and 87.2% in the TAC-PL group and 98.7% and 94.7% in TAC-ST group (P = 0.096 and P = 0.093, respectively). Three- and 12-month graft survival rates were 92.3% and 85.9% versus 97.4% and 92.3% (P = 0.14 and 0.13, respectively). By 3 and 12 months, rejection treatment had been given in 20.5% (16 pts) and 23% (18 pts) of TAC-PL patients and in 12.7% (10 pts) and 20.5% (16 pts) of TAC-ST patients (P = 0.20 and 0.54). Corticosteroid-resistant rejection (CRR) at 3 and 12 months was recorded in 12.8% (10 pts) of TAC-PL patients and 3.8% (3 pts) of TAC-ST patients (P = 0.04). When considering the 145 patients transplanted without artificial organ support (n = 145), CRR at 3 and 12 months was recorded in 8.8% (6/68 pts) of TAC-PL patients and in 3.9% (3/77 pts) of TAC-ST patients (P = 0.22). Vanishing bile duct syndrome was diagnosed in 1 (1.2%) TAC-PL patient and 4 (5.1%) TAC-ST patients (P = 0.17). By 1 year, 78.2% (61/78) of TAC-PL patients and 82% (64/78) of TAC-ST patients were on TAC monotherapy (P = 0.54). When considering 67 TAC-PL and 74 TAC-ST survivors, rates of monotherapy were 91% (61 pts) and 86.5% (64 pts) (P = 0.39). At 1 year, 62.5% (42 pts) of TAC-PL survivors and 64.9% (48 pts) of TAC-ST survivors were on low-dosage (<6 ng/mL) TAC monotherapy (P 0.79).

CONCLUSION

TAC monotherapy can be achieved safely without compromising graft nor patient survival in a primary, even unselected, adult liver transplant population. The higher incidence of early CRR in the TAC-PL group related to the significantly higher number of patients transplanted while being on artificial organ support. In such condition, this monodrug immunosuppressive strategy needs to be adapted. TAC monotherapy strategy should lay the basis for further large scale minimization studies in liver transplantation.

Effect of immunosuppressants on the expansion and function of naturally occurring regulatory T cells

The induction of immune tolerance is one of the final therapeutic goals in clinical transplantation. Regulatory T lymphocytes are important for the induction and maintenance of immune tolerance to grafts. If immunosuppressive drugs used clinically to prevent immune rejection also inhibit regulatory T lymphocytes, tolerance would not be achieved. We therefore tested the effect of several immunosuppressants with different mechanisms of action on the proliferation and suppressive activity of CD4(+)CD25(+) regulatory T cells. Highly purified CD4(+)CD25h(+) T cells from C57BL/6 (H-2(b)) mice were stimulated with allogeneic T-depleted splenocytes (BALB/c; H-2(d)) in the presence of various immunosuppressants. After one week in culture, viable T cells were recovered, their regulatory capacity was assessed by their ability to inhibit responder T cell proliferation in MLR, and their cytokine production profile was measured by ELISA. The immunosuppressants rapamycin, cyclosporine A, and methylprednisolone significantly inhibited the expansion of regulatory T cells upon stimulation with alloantigen, whereas mycophenolic acid and the costimulatory blockers, anti-CD40L and CTLA4Ig, did not. None of these immunosuppressants, however, reduced the suppressive capacity of regulatory T cells. Pretreatment with immunosuppressants did not induce significant changes in the cytokine production profile of regulatory T cells. Our results suggest that costimulatory blockers and mycophenolate mofetil can be utilized therapeutically in the induction of immune tolerance. In contrast, the use of rapamycin, cyclosporine A, and methylprednisolone should be reconsidered, due to their deleterious effects on the expansion of naturally occurring regulatory T cells.

Long-Term Cell Monitoring of Kidney Recipients After an Antilymphocyte Globulin Induction With and Without Steroids

BACKGROUND

Because of several side effects, the corticosteroid usage has been minimized in kidney transplantation. The increased acute rejection episodes associated with their withdrawal may counterbalance with induction treatment using polyclonal antilymphocyte globulin (ALG). The effects of ALG on blood cell phenotype have already been the subject of several reports. However, to date, no data are available concerning the comparison of blood phenotype when ALG is given with or without steroids and no gene profiling study has been performed.

METHODS

We report here on a longitudinal blood cell analysis of a selected cohort of kidney recipients enrolled in a randomized study of steroid avoidance or withdrawal (during 6 months) during ALG induction.

RESULTS

In the two groups, ALG quickly and massively depleted all the T cells and natural killer cells, but not B cells. Interestingly, the lymphopenia-driven homeostatic proliferation of CD4 and CD8T cells strongly differed with persistent low CD4 (including CD25CD4) T-cell counts. Effector memory CD8T cells reappeared rapidly. ALG induced apoptosis-associated molecules and increased myeloid cell genes. However, few genes were found differentially expressed with a low fold ratio between the two groups during and at distance of corticotherapy.

CONCLUSION

Thus initial steroid avoidance or withdrawal associated with ALG induction has a weak influence on phenotype and transcriptional pattern of blood leukocytes. In contrast, ALG therapy induces an early and strong depletion of all T-cell subsets with contrasted long-lasting homeostatic regulation.

Steroids in intestinal transplantation

BACKGROUND

Recently, new immunosuppressive protocols after intestinal transplantation have been proposed to avoid steroids use and their adverse effects. We evaluated the impact of steroids on survival and post-transplant complications in our experience.

PATIENT AND METHODS

In our retrospective study we considered the mean daily dosage of steroids received by 25 patients after intestinal/multivisceral transplantation (minimal follow-up was six months). We analyzed graft and patient survival rates, correlation with rejection and infectious episodes and steroids side effects.

RESULTS

After a mean follow-up of three yr, we did not find any significant difference in steroid doses between our immunosuppressive protocols. Patients with a mean dosage of prednisone higher than 20 mg/d experienced a lower graft (p = 0.009) and patient (p = 0.02) survival rate. The side effects of steroids after transplant were similar. Infections were more frequent during steroids administration (p = 0.04).

DISCUSSION AND CONCLUSION

Steroids therapy may be useful to treat acute rejection, but in our experience high steroids regimen did not improve graft and patient survival, increasing infectious rate. We assumed that high dose of steroids can be avoided as maintenance therapy, except in selected cases.

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.

Study of the impact of liver transplantation on the outcome of intestinal grafts in children

BACKGROUND

Successful small bowel transplantation remains a challenge due to the septic and immune content of the gut. The possible beneficial role of the liver was assessed in pediatric recipients of isolated intestinal and liver intestinal combined transplantation, receiving the same immunosuppressive therapy.

METHODS

Fifteen children who underwent small bowel transplantation (seven SbTx) or combined liver-small bowel transplantation (eight LSbTx) at a single center between 1994 and 1998 were retrospectively reviewed and compared with fifteen controls (eight normal and seven appendicitis as inflammatory control). Transplant and patient survival, acute rejection episodes were analyzed and compared. Epithelial apoptotic body counts (ABC) and NF-kB (p65), Caspase-3 and Bax intestinal immunostaining from days 0 to 20 after transplantation were assessed.

RESULTS

Graft and patient survivals at 5 years were respectively 75% and 75% in LSbTx; 43% and 57% in SbTx (NS). Histological analysis showed higher ABC in LSbTx intestinal mucosa (P = 0.05 on day 5, P < 0.01 thereafter). Immunostaining of biopsies on day 0 after reperfusion showed different expression of NF-kB, Caspase-3 and Bax on endothelial (P < 0.05 for NF-kB and Bax), mononuclear (P < 0.05 for Bax) and epithelial cells in LSbTx and SbTx.

CONCLUSIONS

Our results suggest a protective role of the liver toward intestinal transplantation even in absence of significative difference, probably due to the small number of children. Early changes in NF-kB immunostaining in the biopsies sampled on day 0, pointed to a possible beneficial effect of the liver in the very early phase following transplantation, perhaps through the differential control of ischemia-reperfusion.

Effect of prednisone versus no prednisone as part of maintenance immunosuppression on long-term renal transplant function

Corticosteroids have been a component of maintenance immunosuppression for renal transplant since the 1960s and have helped to reduce the rate of acute rejection. Corticosteroids, however, have many adverse effects, and with the development of new immunosuppressive medications, many transplant centers have adopted protocols that eliminate or completely avoid the use of corticosteroids. Despite promising short-term results, the impact of corticosteroid elimination on long-term kidney function still is unclear. This single-center, retrospective, sequential study analyzed 212 renal transplant patients with a median follow-up of 5 yr. All patients received induction with IL-2 receptor antagonist and maintenance immunosuppression with mycophenolate mofetil and tacrolimus. Ninety-six patients were maintained on chronic prednisone, and 116 were maintained without chronic prednisone (rapid steroid elimination). Kaplan-Meier patient and graft survival at 7 yr after transplantation were not statistically different between the two groups. Rate and severity of acute cellular rejection were similar. Furthermore, the slope of GFR decline per month at 5 yr after transplantation was not statistically different between the two groups. Prednisone-treated patients had a significantly higher incidence of hyperlipidemia and posttransplantation diabetes when compared with patients with rapid steroid elimination. It was concluded that with the current immunosuppressive medications, the use of chronic prednisone to maintain long-term kidney function and prevent acute cellular rejection is not justified.

Attenuation of acute rejection in a rat liver transplantation model by a liver-targeted dextran prodrug of methylprednisolone

BACKGROUND

The use of methylprednisolone (MP) and other corticosteroids for the treatment of acute liver allograft rejection is associated with severe toxicities in nontarget tissues. Therefore, selective delivery of MP to the liver may improve its efficacy and alleviate its side effects. We investigated the effects of a novel liver-targeted dextran prodrug of MP (DMP) in an orthotopic rat liver transplantation (OLT) model.

METHODS

The model consisted of a high responder rejection strain combination (Dark Agouti donors and Lewis recipients). Liver recipients were intravenously administered saline or a single subtherapeutic dose of MP (5 mg/kg) as the parent drug (MP) or its prodrug (DMP). Different groups were then monitored for graft survival or euthanized 5 or 9 days posttransplantation. Plasma chemistry, including alkaline phosphatase and bilirubin, allograft histology, and survival duration were determined.

RESULTS

Untreated recipients exhibited elevated plasma levels of liver injury markers, progressive portal and venous inflammation and cellular infiltration in liver allografts, and a mean graft survival time (MST) of 10.5 days. MP treatment did not alter any of these parameters. In contrast, a single dose of DMP resulted in a decrease in plasma levels of liver injury markers, a decrease in histological grade of rejection on day 5, and a substantial increase in MST (27.5 days).

CONCLUSIONS

These results demonstrate attenuation of acute rejection following local (allograft) immunosuppression with a single subtherapeutic dose of MP delivered as a liver-targeted prodrug. Dextran prodrugs may be useful for selective delivery of immunosuppressants to the liver following liver transplantation.

Immunosuppression without steroids in liver transplantation is safe and reduces infection and metabolic complications: results from a prospective multicenter randomized study

BACKGROUND/AIMS

The purpose of this study was to evaluate the efficacy of a steroid-free immunosuppression protocol.

METHODS

From 2001 to 2004, 198 liver-transplant patients were randomized to receive immunosuppression with Basiliximab and cyclosporine, with (St Group) or without (NoSt Group) prednisone. The primary end points were acute rejection, and patient and graft survival. The secondary end points were infection, metabolic complications, and hepatitis C-virus recurrence.

RESULTS

Overall rejection rate was 15%, with no differences (St: 13% vs NoSt: 18%; P=0.33). Infection rate was similar in both groups (St: 51% vs NoSt: 47%; P=0.56), but diabetic patients in the St Group had a significantly higher rate of bacterial infections (St: 54% vs NoSt: 14%; P=0.005). The six-month protocol biopsies showed hepatitis C recurrence in 90% of patients, without differences between groups. Hypertension was more frequent in the St Group (St: 44% vs NoSt: 25%; P=0.006). De novo diabetes rate was higher in the St Group (month 1: St: 29% vs NoSt: 18%; P=0.06), with higher glycatedHb (5.1+/-1.1 vs 4.4+/-0.8; P=0.002). Six-month survival rates were similar (St: 89% vs NoSt: 94%, P=0.62).

CONCLUSIONS

Immunosuppression without steroids is safe and reduces infection and metabolic complications.

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 unfinished legacy of liver transplantation: emphasis on immunology

Liver transplantation radically changed the philosophy of hepatology practice, enriched multiple areas of basic science, and had pervasive ripple effects in law, public policy, ethics, and theology. Why organ engraftment was feasible remained enigmatic, however, until the discovery in 1992 of donor leukocyte microchimerism in long-surviving liver, and other kinds of organ recipients. Following this discovery, the leukocyte chimerism-associated mechanisms were elucidated that directly linked organ and bone marrow transplantation and eventually clarified the relationship of transplantation immunology to the immunology of infections, neoplasms, and autoimmune disorders. We describe here how the initially controversial paradigm shift mandated revisions of cherished dogmas. With the fresh insight, the reasons for numerous inexplicable phenomena of transplantation either became obvious or have become susceptible to discriminate experimental testing. The therapeutic implications of the "new immunology" in hepatology and in other medical disciplines, have only begun to be explored. Apart from immunology, physiologic investigations of liver transplantation have resulted in the discovery of growth factors (beginning with insulin) that are involved in the regulation of liver size, ultrastructure, function, and the capacity for regeneration. Such studies have partially explained functional and hormonal relationships of different abdominal organs, and ultimately they led to the cure or palliation by liver transplantation of more than 2 dozen hepatic-based inborn errors of metabolism. Liver transplantation should not be viewed as a purely technologic achievement, but rather as a searchlight whose beams have penetrated the murky mist of the past, and continue to potentially illuminate the future.

Steroid-free immunosuppression in organ transplantation

Although steroids have been the cornerstone of immunosuppressive regimens to treat and prevent rejection in organ transplantation, the past decade has seen many successful attempts to minimize or eliminate steroid use. This has been undertaken to decrease the diverse side effects seen with chronic steroid treatment. These efforts have focused on both steroid avoidance and complete elimination, and have been successful across broad patient groups. The key to these efforts has been the adoption of induction protocols with either lymphocyte-depleting agents or anti-interleukin-2 strategies, coupled with the use of the newer maintenance immunosuppressants. In this review, we address the feasibility and benefits of steroid-free and steroid avoidance protocols in kidney, pancreas, liver, and heart transplantation.

Tolerance: is it worth the risk?

BACKGROUND

The success of orthotopic liver transplantation (OLT) has been limited by the adverse effects of immunosuppression. The purpose of this study was to determine the safety and feasibility of withdrawing immunosuppression in OLT recipients to achieve tolerance.

METHODS

Eighteen adult OLT recipients in our steroid-free protocol without rejection were selected for this protocol. All patients chosen for this trial were on tacrolimus monotherapy with normal liver function tests (LFTs). Tacrolimus was weaned as long as LFTs remained stable. Weaning was halted for elevations of liver enzymes and tacrolimus was increased to the last dosage at which the patients had normal LFTs. Rejection was treated by increasing tacrolimus to levels of 10-15 ng/ml. Mycophenolate mofetil (MMF) or sirolimus was added if there was severe rejection by biopsy. Steroids were used if there was no improvement.

RESULTS

One patient has been weaned off immunosuppression. Three additional patients were weaned completely off but had tacrolimus resumed because of mild elevations in LFTs. Eleven of 18 (61%) patients had rejection. Two patients required steroid therapy and one required rabbit antithymocyte globulin in addition to MMF and steroids. One of the patients with rejection developed diabetes and one patient had renal failure, which subsequently resolved. One patient died following a stroke.

CONCLUSIONS

Clinical tolerance can be achieved in a minority of patients, even when being maintained on minimum immunosuppression. The potential benefit of achieving tolerance must be weighed against the risks of rejection therapy in patients doing well on low-dose immunosuppression.

Posttransplant Interleukin-4 Treatment Converts Rat Liver Allograft Tolerance to Rejection

BACKGROUND

Previous studies showed that liver transplant rejection in the Piebald Virol Glaxo (PVG)-to-Lewis combination was associated with more intragraft interleukin (IL)-4 mRNA expression than in spontaneously tolerant grafts in the PVG-to-Dark Agouti (DA) combination. There was also immunoglobulin (Ig) G1 antibody deposition, suggesting an IL-4-induced IgG class switch in rejection. The aim of this study was to investigate whether IL-4 treatment converts PVG-->DA liver transplant tolerance to rejection.

METHODS

DA (RT1a) rats were recipients of orthotopic PVG (RT1c) liver transplants and DA liver transplants were syngeneic controls. Supernatant from IL-4-transfected Chinese hamster ovary cells (0.5 mL, 30,000 U) or from untransfected cells was injected intraperitoneally on days 3 through 7. Samples were taken for immunohistochemical staining of frozen tissue sections to analyze cellular infiltrate and antibody deposition.

RESULTS

IL-4 treatment significantly reduced survival of liver allografts from greater than 100 days in untreated animals to 9 days (P=0.004). Pathologic analysis of IL-4-treated animals showed that death was caused by liver transplant rejection, with a heavy infiltrate of mononuclear cells, disruption of portal tract areas, and infarction. Immunohistochemistry revealed an extensive infiltrate of T cells, CD25-expressing cells, and B cells that was similar to the level in PVG--> Lewis liver allograft recipients that reject the liver. There was also a more extensive monocyte-macrophage infiltrate and more major histocompatibility complex class II expression in IL-4-treated animals compared with untreated animals. There was moderate increase of IgM, little IgG1, and no IgE or IgG2a antibody deposition.

CONCLUSIONS

IL-4, a T-helper type 2 cytokine that has previously been shown to inhibit delayed-type hypersensitivity responses such as rejection, was found to promote rejection of liver allografts. There was only slight evidence of a graft-specific antibody response, showing that IL-4 induces liver allograft rejection in association with some, but not all, of the changes accompanying rejection in the PVG-->Lewis strain combination.

Strain-specific in vitro cytokine production profiles do not predict rat liver allograft survival

The aim of this study was to assess whether differences in cytokine production between inbred rat strains could explain differences in liver allograft survival. Splenocytes from five different strains were cultured with Concanavalin A to determine in vitro cytokine production profiles. Strain-specific TNF-alpha, IFN-gamma, IL-6 and IL-10 responses in naive animals were not associated with survival after rat liver transplantation. To investigate whether in vitro cytokine responses changed during the allogeneic inflammatory response, Brown Norway livers were transplanted to Lewis and Pivold Virol Glaxo recipients. During the early postoperative phase IL-6 and IL-10 (Th2-like) responses were significantly up-regulated in Lewis recipients, whereas Th2-like responses were not increased in Pivold Virol Glaxo. Our results do not support the generally held view that differential in vitro cytokine responses are related to liver allograft survival but suggest that cytokine responses are affected by the allogeneic inflammatory response after liver allografting.

Corticosteroid avoidance in pediatric renal transplantation: can it be achieved?

Corticosteroids have been a cornerstone therapy in renal transplantation, which is the treatment modality of choice for adult and pediatric end-stage renal disease. Their use is associated with significant morbidity, notably cardiovascular, endocrine, and bone complications, body disfiguration, and almost universal growth retardation in children. While newer immunosuppressants have reduced the incidence of these adverse effects, they continue to pose significant post-transplant challenges. There are various strategies that can be used to avoid these adverse effects including the use of an alternative corticosteroid such as deflazacort, minimization of corticosteroid dosage, corticosteroid withdrawal after a period of early use, and more recently complete corticosteroid avoidance. Recent randomized studies have demonstrated significant improvement in growth parameters, lipid profile, and in the amount of bone loss in patients treated with deflazacort, an oxazoline analog of prednisone, compared with methylprednisone.Corticosteroid minimization has been associated with an increased rate of acute rejection. While augmentation with newer immunosuppressants has helped reduce the incidence of acute rejection, significant improvements in growth have not been demonstrated. Alternate-day corticosteroid therapy has been shown to have a beneficial effect on growth but regimen compliance has limited its widespread applicability. Studies of corticosteroid withdrawal have met with varied success. Early corticosteroid withdrawal has been associated with rejection rates ranging from 10% to 81% and late corticosteroid withdrawal, from 13% to 68.8%, with acute rejection episodes occurring as late as 4 years after corticosteroid withdrawal. The rates of clinical acute rejection have been unacceptably high, and corticosteroid withdrawal is thus used very sparingly in adults and even less so in children. Complete corticosteroid avoidance as reported by an initial study has been associated with a 23% incidence of acute rejection and 'catch-up' growth post-transplantation in 14 pediatric recipients, as measured by the change in height standard deviation scores post-transplantation. A second renal transplant study, in adults, demonstrated similar rejection rates of 25% with improvement in post-transplant hypertension and lipid profiles. A more recent pediatric study using a novel extended daclizumab induction protocol demonstrated an 8% incidence of clinical acute rejection with significant improvements in graft function, hypertension, and growth, without an increased incidence of infectious complications. Renal transplantation with a corticosteroid-free protocol may offer significant advantages in the incidence of acute rejection, graft function, growth, blood pressure, lipidemia, and body appearance and appears to be well tolerated when used with a variety of current induction protocols to replace early corticosteroid use. This protocol may also be applicable to other areas of solid organ transplantation in all age groups.

Combined donor leucocyte administration and immunosuppressive drug treatment for survival of rat heart allografts

BACKGROUND

Donor leucocytes (DL) play an important role in rat liver transplant tolerance and their postoperative administration can convert rejection to tolerance. They appear to induce early activation, altered patterns of infiltration and death of recipient alloreactive T cells. The ability of immunosuppressive drugs to combine with DL administration was examined in a rat heart transplant model.

METHODS

Immediately after PVG to DA heterotopic heart transplantation, 6 x 10(7) spleen DL were injected. Cyclosporine A (CsA), 1.5 mg/kg/day, or methotrexate (MTX), 0.1 or 0.2 mg/kg/day, were given from day (d) 0 to d4 (early) or from d3 to d7 (delayed). Castanospermine (CAST) was administered from d0 to d7 at 100 or 300 mg/kg/day. In a separate experiment, transplanted hearts and recipient spleens were collected from treatment groups for analysis of infiltrate and cytokine mRNA expression.

RESULTS

Delayed treatment with CsA or early treatment with MTX but not CAST combined with DL to result in prolonged graft survival. Recipients treated with DL and delayed CsA had a reduced level of intra-graft interleukin (IL)-2, interferon (IFN)-gamma, IL-4, and IL-4R mRNA expression and reduced infiltrate compared to DL alone. Early MTX plus DL led to almost complete inhibition of all markers of inflammation during treatment followed by a rapid increase after cessation. In combination with DL, CsA was more effective than MTX for induction of donor-specific tolerance at the dose and administration regimens tested.

CONCLUSIONS

Delayed CsA or early MTX combine with DL to prolong heart allograft survival. Early and extensive inhibition of rejection by MTX was less effective than delayed and partial inhibition of the response by CsA for induction of transplant tolerance.

Donor-specific B-cell tolerance after ABO-incompatible infant heart transplantation

Although over 50 years have passed since its first laboratory description, intentional induction of immune tolerance to foreign antigens has remained an elusive clinical goal. We previously reported that the requirement for ABO compatibility in heart transplantation is not applicable to infants. Here, we show that ABO-incompatible heart transplantation during infancy results in development of B-cell tolerance to donor blood group A and B antigens. This mimics animal models of neonatal tolerance and indicates that the human infant is susceptible to intentional tolerance induction. Tolerance in this setting occurs by elimination of donor-reactive B lymphocytes and may be dependent upon persistence of some degree of antigen expression. These findings suggest that intentional exposure to nonself A and B antigens may prolong the window of opportunity for ABO-incompatible transplantation, and have profound implications for clinical research on tolerance induction to T-independent antigens relevant to xenotransplantation.

Chimerism and tolerance in transplantation

Studies in experimental models (1953-1956) demonstrated that acquired donor-specific allotolerance in immunologically immature or irradiated animals is strongly associated with donor leukocyte chimerism. Bone marrow transplantation in immune-deficient or cytoablated human recipients was a logical extension (1968). In contrast, clinical (1959) and then experimental organ transplantation was systematically accomplished in the apparent absence of leukocyte chimerism. Consequently, it was assumed for many years that success with organ and bone marrow transplantation involved fundamentally different mechanisms. With the discovery in 1992 of small numbers of donor leukocytes in the tissues or blood of long-surviving organ recipients (microchimerism), we concluded that organ engraftment was a form of leukocyte chimerism-dependent partial tolerance. In this initially controversial paradigm, alloengraftment after both kinds of transplantation is the product of a double immune reaction in which responses, each to the other, of coexisting donor and recipient immune systems results in variable reciprocal clonal exhaustion, followed by peripheral clonal deletion. It was proposed with Rolf Zinkernagel that the individual alloresponses are the equivalent of the MHC-restricted T cell recognition of, and host response to, intracellular parasites and that the mechanisms of immune responsiveness, or nonresponsiveness, are governed by the migration and localization of the respective antigens. Elucidation of the mechanisms of nonresponsiveness (clonal exhaustion-deletion and immune ignorance) and their regulation removed much of the historical mystique of transplantation. The insight was then applied to improve the timing and dosage of immunosuppression of current human transplant recipients.

Revisiting liver transplant immunology: from the concept of immune engagement to the dualistic pathway paradigm

Ever since the demonstration that allografts are rejected through immune reactions of the host, clinical therapies for organ allografts have relied on immune suppression to prevent these destructive events. A growing body of clinical and experimental data suggests that allografts elicit multiple, interactive immune responses. The result is not inevitably graft rejection, and "spontaneous" acceptance of fully allogeneic liver grafts occurs in rodents without immunosuppression. A spectrum of results range from spontaneous acceptance without immunosuppression to rejection with immunosuppression. The "dualistic pathway paradigm" aims to reconcile apparently conflicting observations in liver transplantation and proposes that: (1) immune engagement between the host and the allograft is instrumental in both rejection and acceptance; (2) there exist in all mammalian species congruent interactive pathways of immune activation whereby the fate of the allograft is determined by the quantitative results of these interactions; (3) the dualistic effect of immunosuppressive drugs on pathways of immune activation, conferring the capacity for favorable or unfavorable graft outcome should be investigated in experimental models in which organ allografts are spontaneously accepted. In conclusion the design of clinical strategies based on this research may contribute to protocols resulting in allograft acceptance without chronic immunosuppression.

Promising early results with immunosuppression using rabbit anti-thymocyte globulin and steroids with delayed introduction of tacrolimus in adult liver transplant recipients

Induction therapy with T-cell depleting drugs in liver transplantation is controversial. This study examined the use of rabbit antithymocyte globulin (RATG) with delayed introduction of tacrolimus in liver transplant recipients. Additional subgroup analysis compared patients with or without hepatitis C (HCV) cirrhosis. Over 17 months, 116 adults received 120 liver allografts. Four patients who died before receiving RATG were excluded. Immunosuppression included steroids, 3 doses of RATG (2 mg/kg), and tacrolimus started on postoperative day 3 to 4. Ninety-six percent of patients were alive with a mean follow-up of 12.9+/-4.5 months. No graft was lost to rejection. Two patients developed hepatic artery thrombosis. Six percent of patients had acute rejection. No patient had steroid resistant or recurrent rejection. RATG related drug events were limited to fever, chills, tachycardia, and oxygen desaturation. There were no cases of lymphoproliferative disease. Forty-two percent of patients were transplanted for HCV. Thirty-two percent of HCV-patients had biopsy proven hepatitis C recurrence occurring at 4 weeks to 10 months posttransplant. RATG induction therapy is associated with good patient and graft survival, a low incidence of rejection, and minimal side effects. In addition, RATG induction is safe in patients transplanted for HCV.

Steroid-free liver transplantation in children

Although corticosteroids have been part of immunosuppressive regimens since the early days of transplantation, steroid avoidance could be beneficial. To test this hypothesis in paediatric liver transplantation, we compared liver-transplantation under steroid-free immunosuppression in 20 children, who received combined tacrolimus and basiliximab, with that under tacrolimus and steroids in 20 matched historical recipients as a historical control group. 12-month rejection-free survival was 75% in the tacrolimus-basiliximab group compared with 50% in the steroid group (p=0.05). Growth in the first year after transplantation was significantly better in the tacrolimus-basiliximab group than in the steroid group. Steroid avoidance was, therefore, not harmful to our patients, and combining tacrolimus with basiliximab as a steroid substitution seems a safe alternative to tacrolimus and steroid immunosuppression.

A short course of mycophenolate immunosuppression inhibits rejection, but not tolerance, of rat liver allografts in association with inhibition of interleukin-4 and alloantibody responses

BACKGROUND

Some immunosuppressive drug therapies inhibit transplant tolerance in animal models, and we have shown that treatment of recipients with methylprednisolone, but not cyclosporine, inhibits spontaneous acceptance of liver transplants. This study investigates the effects of mycophenolate mofetil (MMF) on liver acceptance and rejection.

METHODS

Piebald Virol Glaxo rat livers were transplanted into Dark Agouti recipients, which spontaneously tolerate (TOL) the liver, or into Lewis recipients, which reject (REJ) the liver. MMF (40 mg/kg/day subcutaneously) was given for 5 days from days 0 to 4 (early) or from days 3 to 7 (late). In separate experiments, liver grafts were collected for assessment of infiltrate and of interleukin (IL)-2, IL-4, IL-10, and interferon-gamma mRNA expression.

RESULTS

TOL liver transplants had a median survival time (MST) of more than 100 days (n=6), and neither early nor late MMF treatment of TOL transplants reduced survival (MST 85 days, P=0.19 and 78 days, P=0.08, respectively). Liver failure in most of these animals was the result of biliary problems, not rejection. There were few consistent differences between treated and untreated TOL animals in infiltrate or liver cytokine expression, although there was a moderate reduction in T-cell infiltrate in MMF-treated TOL animals (P=0.003 on day 5 TOL). In contrast, REJ transplants had an MST of 13 days (n=10), and early MMF treatment led to five of six animals surviving more than 100 days (P=0.0002), whereas late treatment was much less effective, with one of six animals surviving more than 100 days. REJ livers had significantly more IL-4 mRNA expression and immunoglobulin G1 deposition in the graft than TOL livers, and this was inhibited by early, but not late, MMF treatment.

CONCLUSIONS

MMF treatment inhibited rejection but not acceptance of liver allografts. Early administration was more effective in preventing rejection and demonstrated a more marked effect on IL-4 expression and alloantibody deposition than on graft T-cell infiltrate and expression of other cytokines.

Tolerogenic immunosuppression for organ transplantation

BACKGROUND

Insight into the mechanisms of organ engraftment and acquired tolerance has made it possible to facilitate these mechanisms, by tailoring the timing and dosage of immunosuppression in accordance with two therapeutic principles: recipient pretreatment, and minimum use of post-transplant immunosuppression. We aimed to apply these principles in recipients of renal and extrarenal organ transplants.

METHODS

82 patients awaiting kidney, liver, pancreas, or intestinal transplantation were pretreated with about 5 mg/kg of a broadly reacting rabbit antithymocyte globulin during several hours. Post-transplant immunosuppression was restricted to tacrolimus unless additional drugs were needed to treat breakthrough rejection. After 4 months, patients on tacrolimus monotherapy were considered for dose-spacing to every other day or longer intervals.

FINDINGS

We frequently saw evidence of immune activation in graft biopsy samples, but unless this was associated with graft dysfunction or serious immune destruction, treatment usually was not intensified. Immunosuppression-related morbidity was virtually eliminated. 78 (95%) of 82 patients survived at 1 year and at 13-18 months. Graft survival was 73 (89%) of 82 at 1 year and 72 (88%) of 82 at 13-18 months. Of the 72 recipients with surviving grafts, 43 are on spaced doses of tacrolimus monotherapy: every other day (n=6), three times per week (11), twice per week (15), or once per week (11).

INTERPRETATION

The striking ability to wean immunosuppression in these recipients indicates variable induction of tolerance. The simple therapeutic principles are neither drug-specific nor organ-specific. Systematic application of these principles should allow improvements in quality of life and long-term survival after organ transplantation.

Steroid-free liver transplantation using rabbit antithymocyte globulin and early tacrolimus monotherapy

BACKGROUND

In 2001, we published early results of a prospective randomized trial of 71 patients who received either steroids or rabbit antithymocyte globulin (RATG) for orthotopic liver transplantation (OLT). We now report follow-up on these patients and additional patients undergoing steroid-free OLT.

METHODS

A total of 119 adult OLT recipients were prospectively randomized to receive either methylprednisolone 1,000 mg followed by a 3-month steroid taper or a steroid-free regimen of RATG 1.5 mg/kg during the anhepatic phase followed by a 1.5 mg/kg dose on posttransplant day 1. Maintenance immunosuppression consisted of tacrolimus and mycophenolate mofetil in both groups. Mycophenolate mofetil was weaned over 3 months in the first 71 patients and over 2 weeks in the last 48 patients, achieving tacrolimus monotherapy by 2 weeks posttransplant. Subsequently, a group of 24 sequential OLT recipients received the steroid-free (RATG) protocol. Endpoints of the study were survival, rejection, infectious complications, posttransplant diabetes, and recurrent hepatitis C virus.

RESULTS

One-year patient survival was 85% in each group of the prospective randomized trial with a mean follow-up of 18.5 months. One-year graft survival was 82% in the RATG group and 80% in the steroid group (P=not significant). Patient and graft survival of the 24 nonrandomized RATG patients was 96% with a mean follow-up of 3 months. The incidence of rejection was not significantly different; however, 50% of the patients in the steroid group required pulse steroids to reverse the rejection compared with only one patient (1.6%) in the RATG group (P=.03). The incidence of cytomegalovirus infection (P<.05) and posttransplant diabetes was higher in the steroid group (P=.03). There was a trend toward decreased severity of hepatitis C virus in the RATG group.

CONCLUSIONS

Steroid-free liver transplantation using RATG and early tacrolimus monotherapy effectively reduces immunosuppression-related complications with excellent survival.

A short course of cyclosporine immunosuppression inhibits rejection but not tolerance of rat liver allografts

BACKGROUND

Orthotopic liver transplants in many animal models are spontaneously accepted without requiring immunosuppression. Liver transplant acceptance is associated with early immune activation, and immunosuppressive drugs such as methylprednisolone inhibit acceptance. We investigated whether cyclosporine (CsA) inhibits rat liver transplant acceptance. We also examined the effects of CsA on infiltration and cytokine gene expression.

METHODS

Orthotopic liver transplantation was performed in the PVG donor to Dark Agouti recipient rat strain combination, which accepts the graft (tolerance; TOL), and in the PVG-to-Lewis combination, which rejects the graft in 9 to 16 days (rejection; REJ). CsA (1.5 mg/kg per day subcutaneously) was given to recipients for 5 days, starting from the day of transplantation to day 4 or from day 3 to day 7. In a separate experiment, transplanted livers were collected at days 1, 3, 5, and 7 after transplantation and examined for infiltration by immunohistochemistry and for expression of interleukin (IL)-2, IL-4, IL-10, and interferon-gamma mRNA by quantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Both early and delayed treatment with CsA significantly increased survival in the REJ strain combination, with a median survival time of 81 days and more than 100 days, respectively, compared with 13 days in the untreated group. Neither treatment affected survival of TOL animals, and all TOL groups had a median survival time of more than 100 days. Delayed treatment did not reduce survival; more animals survived for greater than 100 days after delayed treatment, although this did not reach significance ( P=0.08). T-cell infiltrate was inhibited in CsA-treated TOL animals compared with untreated animals at all times after treatment, whereas CD25 cells were only inhibited on day 3. CsA treatment of TOL grafts markedly reduced expression of IL-2, IL-4, and interferon-gamma compared with untreated recipients.

CONCLUSIONS

CsA did not significantly inhibit liver transplant acceptance and allowed some activation of T cells and CD25 expression but almost completely inhibited IL-2 and IL-4, which are required for survival of activated T cells.

Spontaneous acceptance of liver transplants in rodents: evidence that liver leucocytes induce recipient T-cell death by neglect

In many animal models transplanted livers are not rejected, even when there is a complete MHC mismatch between the donor and recipient and the recipient is not immunosuppressed. This distinguishes liver transplants from other organs, such as kidneys and hearts, which are rapidly rejected in mismatched individuals. Acceptance of transplanted livers in a rat model is not due to the absence of an immune response to the liver and there is a rapid, abortive response that is ultimately exhausted. Donor leucocytes transferred with the liver appear to be responsible for both liver acceptance and the abortive activation of the recipient's T cells. The immune mechanism of liver transplant acceptance appears to be due to 'death by neglect' in which T cells are activated to express IL-2 and IFN-gamma mRNA in the recipient lymphoid tissues, but not at adequate levels within the graft. Subsequently the activated T cells die leading to specific clonal deletion of liver donor-reactive T cells. These findings have important implications for liver transplant patients as immunosuppressive drugs that are given to prevent rejection can also interfere with this form of tolerance. In addition, it might be possible to modify the immunosuppressive drug treatment of transplant patients to promote the process of death by neglect of recipient alloreactive T cells.