Undetected hepatocellular carcinoma in patients undergoing liver transplantation: is associated with favorable outcome.

BACKGROUND/AIMS: The aim of the study was to define the clinical characteristics and outcome of patients found to have undetected hepatocellular carcinomas (HCC) at liver transplantation. Patients who underwent liver transplantation and were unexpectedly found to have a HCC despite prior workup showing normal alpha-fetoprotein levels and/or no visible radiological lesion were defined as having an undetected HCC. METHODOLOGY: Thirty-two of these patients had a histological diagnosis of HCC in the explanted liver. Undetected HCC was defined as a carcinoma found only on pathological evaluation of the explanted liver, with a pre-OLT workup showing a normal serum alpha-fetoprotein (AFP) level (<20 ng/mL) and/or no suspicious lesion on preoperative radiological evaluation. RESULTS: Nine patients had a tumor that met the criteria for an undetected HCC. The most common cause for transplantation was cryptogenic cirrhosis (44.4%). Tumor size was 2 cm or less in all patients, vascular invasion was detected in 11.1% of the patients, and tumor, node, metastasis (TNM) classification was stage I in 77.8%. Eight patients (88.9%) remained alive at the cessation of the analysis with a mean follow-up of 60 +/- 30.4 months. There was no tumor recurrence in any patient. Statistical analysis showed significant differences between undetected and detected HCCs when causes of pretransplantation liver disease, peak AFP level, tumor size, number of tumors, presence of vascular invasion or pathological differentiation were compared. Undetected HCCs were associated with a better survival rate after liver transplantation (p = 0.008). CONCLUSIONS: Patients with undetected HCCs at OLT have a favorable outcome with tumor-free survival. Most patients had small, early-stage HCCs, but the possibility of finding tumors greater than 2 cm, multifocal lesions, and vascular invasion exist despite thorough investigation. An exhaustive histopathological search of the explant for malignancy will allow for greater accuracy in prognosis.

Measurement and stability of FTY720 in human whole blood by high-performance liquid chromatography-atmospheric pressure chemical ionization-tandem mass spectrometry.

We report here a validated method for the quantification of a new immunosuppressant drug FTY720, using HPLC-tandem mass spectrometry. Whole blood samples (500 microl) were subjected to liquid-liquid extraction, in the presence of an internal standard (Y-32919). Mass spectrometric detection was by selected reaction monitoring with an atmospheric pressure chemical ionization source in positive ionization mode (FTY720: m/z 308.3-->255.3). The assay was linear from 0.2 to 25 microg/l (r(2)>0.997, n=5). The inter- and intra-day analytical recovery and imprecision for quality control samples (0.5, 7 and 15 microg/l) were 95.8-103.2 and <5.5%, respectively. At the lower limit of quantification (0.2 microg/l) the inter- and intra-day analytical recovery was 99.0-102.8% with imprecision of <7.6% (n=5). The assay had a mean relative recovery of 100.5+/-5.8% (n=15). Extracted samples were stable for 16 h. FTY720 quality control samples were stable at room temperature for 16 h, at 4 degrees C for at least 8 days and when taken through at least three freeze-thaw cycles. In conclusion, the method described displays analytical performance characteristics that are suitable for pharmacokinetic studies in humans.

A rapid HPLC-mass spectrometry cyclosporin method suitable for current monitoring practices.

OBJECTIVES: Cyclosporin is an immunosuppressant drug with a narrow therapeutic window. Trough and 2-h post-dose blood samples are currently used for therapeutic drug monitoring in solid organ transplant recipients. The aim of the current study was to develop a rapid HPLC-tandem mass spectrometry (HPLC-MS) method for the measurement of cyclosporin in whole blood that was not only suitable for the clinical setting but also considered a reference method. METHODS: Blood samples (50 muL) were prepared by protein precipitation followed by C(18) solid-phase extraction while using d(12) cyclosporin as the internal standard. Mass spectrometric detection was by selected reaction monitoring with an electrospray interface in positive ionization mode. RESULTS: The assay was linear from 10 to 2000 microg/L (r(2)>0.996, n=9). Inter-day analytical recovery and imprecision using whole blood quality control samples at 10, 30, 400, 1500, and 2000 microg/L were 94.9--103.5% and <7.7%, respectively (n=5). The assay had a mean relative recovery of 101.6%. Ion suppression was<8.0% of the total signal (n=15). Extracted samples were stable for 6 h. Patient samples, measured by this method and compared with a validated HPLC-UV assay, revealed a strong correlation (r=0.998) and excellent agreement with a mean percentage bias of 2.1% (n=60). CONCLUSION: This high-throughput method provides accurate, precise, and specific measurement of cyclosporin in blood over a wide analytical range, thus making it suitable for current clinical monitoring strategies.

Lymphocyte apoptosis and cell replacement in human liver allografts.

BACKGROUND: Apoptosis of graft-infiltrating T cells has been described after rodent liver transplantation. The aim of this study was to assess lymphocyte apoptosis in human allografts. Additionally, kinetics of leukocyte turnover were studied to determine whether apoptotic cells were likely to be of donor or recipient origin. METHODS: Liver biopsy specimens (n=36) taken between days 3 and 1855 were stained with terminal deoxynucleotidyl transferase dUTP nick end-labeling and anti-CD3 to detect apoptotic lymphocytes. Renal allograft and hepatitis C biopsy specimens served as controls. Donor cell turnover was studied in sex-mismatched grafts using Y-chromosome in situ hybridization to detect recipient cells and double immunostaining for leukocyte phenotyping. RESULTS: T-cell apoptosis was prominent in hepatic sinusoids (72% of biopsy specimens) as early as day 3. It ranged from 0% to 18.2% of CD3+ cells (mean 5.28+/-0.82%) and persisted for >14 days, including time points >1 year. There was no difference between biopsy specimens with or without rejection (6.34+/-1.14% and 4.61+/-1.13%, P=NS). Apoptotic cells in portal tracts were less frequent (33% of biopsy specimens) and less abundant (1.13+/-0.36%, P<0.0001). No lymphocyte apoptosis was seen in renal allograft biopsy specimens or hepatitis C biopsy specimens, indicating that it is a distinctive feature of the liver allograft. Persisting lymphocyte apoptosis even after donor lymphocytes had been replaced suggests that recipient lymphocyte deletion must occur. Donor Kupffer cells persisted for many months. CONCLUSIONS: Our results suggest that the sinusoidal microenvironment promotes recipient lymphocyte apoptosis, which may account for the improved outcome of liver grafts compared with other organ allografts.

Quantification and stability of everolimus (SDZ RAD) in human blood by high-performance liquid chromatography-electrospray tandem mass spectrometry.

We report here a validated method for the quantification of a new immunosuppressant drug, everolimus (SDZ RAD), using HPLC-tandem mass spectrometry. Whole blood samples (500 microl) were prepared by protein precipitation, followed by C(18) solid-phase extraction. Mass spectrometric detection was by selected reaction monitoring with an electrospray interface operating in positive ionization mode. The assay was linear from 0.5 to 100 microg/l (r(2) > 0.996, n = 9). The analytical recovery and inter-day imprecision, determined using whole blood quality control samples (n = 5) at 0.5, 1.2, 20.0, and 75.0 microg/l, was 100.3 - 105.4% and < or = 7.6%, respectively. The assay had a mean relative recovery of 94.8 +/- 3.8%. Extracted samples were stable for up to 24 h. Fortified everolimus blood samples were stable at -80 degrees C for at least 8 months and everolimus was found to be stable in blood when taken through at least three freeze-thaw cycles. The reported method provides accurate, precise and specific measurement of everolimus in blood over a wide analytical range and is currently supporting phase II and III clinical trials.

Liver transplantation for hepatolithiasis.

Hepatolithiasis is frequently encountered in Asia, but is relatively uncommon in Western societies. The improved surgical and stone fragmentation techniques that have evolved over the past decade have reduced the incidence of retained or recurrent stones with a consequent reduction in progressive liver damage and cirrhosis. Nonetheless, disease-related mortality from liver failure, bleeding oesophageal varices and cholangiocarcinoma still exists and a proportion of patients are cirrhotic at their initial presentation. There have been good long-term results following liver transplantation for a variety of cholestatic liver diseases, but transplantation for hepatolithiasis has seldom been reported. This paper reports four patients who underwent successful liver transplantation for hepatolithiasis with secondary biliary cirrhosis.

[Liver transplantation for primary biliary cirrhosis: retrospective analysis of 52 patients in QLTS].

OBJECTIVE: Retrospectively analyzing post-transplant primary biliary cirrhosis patients to document the actual survival time, the cause of post-transplant death, and recurrences after liver transplantation in patients followed up by the Queensland Liver Transplant Service (QLTS). METHODS: The case notes of all post-piggyback liver transplantation patients followed up by QLTS were reviewed. We analyzed the clinical characteristics of the PBC patients, post-transplant actual survival rates, the causes of post-transplant death, and risk factors of recurrence, and compared the survival rates between patients with and without liver transplantation using a European model. RESULTS: Fifty-two post-transplant patients with 54 transplantations were identified with an average age of 53 years and a mean follow-up time of 55 months. The actual survival times of PBC patients with grafts for 1 years, 5 years and 10 years were 88.4%, 80.1%, 76.9% and 80.9%, 65.4%, 19.8%. The causes of death were MOF intra-abdominal bleeding, renal failure, sepsis and cardiovascular diseases. Comparing the survival rates between with and without transplantation, 8.5% of PBC patients have recurrences with an average recurrent time of 34 months. CONCLUSION: (1) Liver transplantation could improve survival rates, but the optimum time for transplantation should be focused on; (2) A long-term and larger follow-up sampling should be done to understand the effects of recurrences on patient's long-term survival; (3) CsA may play a more important role in preventing recurrence of PBC than Tacrolimus

Donor-transmitted, donor-derived, and de novo cancer after liver transplant.

Cancer is the third most common cause of death (after cardiovascular disease and infection) for patients who have a functioning kidney allograft. Kidney and liver transplant recipients have similar cancer risks because of immunosuppression but different risks because of differences in primary diseases that cause renal and hepatic failure and the inherent behavior of cancers in the liver. There are 4 types of cancer that may develop in liver allograft recipients: (1) recurrent cancer, (2) donor-transmitted cancer, (3) donor-derived cancer, and (4) de novo cancer. Identification of potential donor cancer transmission may occur at postmortem examination of a deceased donor or when a probable donor-transmitted cancer is identified in another recipient. Donor-transmitted cancer after liver transplant is rare in Australia, the United Kingdom, and the United States. Aging of the donor pool may increase the risk of subclinical cancer in donors. Liver transplant recipients have a greater risk of de novo cancer than the general population, and risk factors for de novo cancer in liver transplant recipients include primary sclerosing cholangitis, alcoholic liver disease, smoking, and increased age. Liver transplant recipients may benefit from cancer screening because they have a high risk, are clearly identifiable, and are under continuous medical supervision.

Living donor liver transplantation--adult donor outcomes: a systematic review.

The objective of this study was to evaluate the safety and efficacy of adult-to-adult living donor liver transplantation, specifically donor outcomes. A systematic review, with searches of the literature up to January 2004, was undertaken. Two hundred and fourteen studies provided information on donor outcomes. The majority of these were case series studies, although there were also studies comparing living donor liver transplantation with deceased donor liver transplantation. Both underreporting and duplicate reporting is likely to have occurred, and so caution is required in interpretation of these results. Overall reported donor mortality was 12 to 13 in about 6,000 procedures (0.2%) (117 studies). Mortality for right lobe donors to adult recipients is estimated to be 2 to 8 out of 3,800 (0.23 to 0.5%). The donor morbidity rate ranged from 0% to 100% with a median of 16% (131 studies). Biliary complications and infections were the most commonly reported donor morbidities. Nearly all donors had returned to normal function by 3 to 6 months (18 studies). In conclusion, there are small, but real, risks for living liver donors. Due to the short history of adult-to-adult living donor liver transplantation, the long-term risks for donors are unknown.

Outcomes of split versus reduced-size grafts in pediatric liver transplantation.

BACKGROUND: Split-liver transplantation, where two grafts are created from a single donor organ, is a means of overcoming donor organ scarcity. There are few data comparing outcomes of split with reduced-size liver grafts, which is the most common type of cadaveric graft in pediatric liver transplantation. The aims of the present paper were to compare survival and complication rates between split and reduced-size cadaveric grafts in pediatric patients receiving a liver transplant in Brisbane. METHODS: Review of the Queensland Liver Transplant Service database was undertaken. All pediatric patients who received either a cadaveric split or reduced-size graft between 1985 and 2000 were examined. The incidence of patient and graft survival, vascular complications and biliary complications were identified. RESULTS: A total of 251 liver transplants were performed of which 138 were reduced-size grafts and 30 were split grafts. There were no differences in etiology of liver disease, mean age, weight, and urgency of transplant between the two groups. One-year patient and graft survivals were comparable at 73% and 67%, respectively, in both groups. There was no difference in the incidence of vascular complications between groups. Biliary complications were significantly more common after split grafts when compared with reduced-size grafts (21%vs 4%, P < 0.0001) but did not affect patient or graft survival. CONCLUSIONS: Survival and vascular complications after split-liver grafts were comparable to outcomes after reduced-size grafts. Biliary complications occur more commonly with split-liver grafts but did not affect patient or graft survival. It is recommended that every pediatric recipient be considered for a split-liver graft.

Toward better outcomes with tacrolimus therapy: population pharmacokinetics and individualized dosage prediction in adult liver transplantation.

Patient outcomes in transplantation would improve if dosing of immunosuppressive agents was individualized. The aim of this study is to develop a population pharmacokinetic model of tacrolimus in adult liver transplant recipients and test this model in individualizing therapy. Population analysis was performed on data from 68 patients. Estimates were sought for apparent clearance (CL/F) and apparent volume of distribution (V/F) using the nonlinear mixed effects model program (NONMEM). Factors screened for influence on these parameters were weight, age, sex, transplant type, biliary reconstructive procedure, postoperative day, days of therapy, liver function test results, creatinine clearance, hematocrit, corticosteroid dose, and interacting drugs. The predictive performance of the developed model was evaluated through Bayesian forecasting in an independent cohort of 36 patients. No linear correlation existed between tacrolimus dosage and trough concentration (r(2) = 0.005). Mean individual Bayesian estimates for CL/F and V/F were 26.5 +/- 8.2 (SD) L/hr and 399 +/- 185 L, respectively. CL/F was greater in patients with normal liver function. V/F increased with patient weight. CL/F decreased with increasing hematocrit. Based on the derived model, a 70-kg patient with an aspartate aminotransferase (AST) level less than 70 U/L would require a tacrolimus dose of 4.7 mg twice daily to achieve a steady-state trough concentration of 10 ng/mL. A 50-kg patient with an AST level greater than 70 U/L would require a dose of 2.6 mg. Marked interindividual variability (43% to 93%) and residual random error (3.3 ng/mL) were observed. Predictions made using the final model were reasonably nonbiased (0.56 ng/mL), but imprecise (4.8 ng/mL). Pharmacokinetic information obtained will assist in tacrolimus dosing; however, further investigation into reasons for the pharmacokinetic variability of tacrolimus is required.

A pharmacodynamic investigation of tacrolimus in pediatric liver transplantation.

Although monitoring of tacrolimus blood concentrations is standard clinical practice following liver transplantation, a greater understanding of the relationship between trough concentrations and clinical outcome is required. The aim of this study was to perform a pharmacodynamic investigation of tacrolimus in pediatric liver transplant recipients. A retrospective analysis was performed on 35 pediatric liver recipients who received oral tacrolimus as the primary immunosuppressant. Outcome data were recorded corresponding to the times that tacrolimus trough concentrations had been determined (using a validated high-performance liquid chromatography-tandem mass spectrometry assay). A Mann-Whitney rank sum test was used to investigate differences between median concentrations at which drug toxicity, infection, and organ rejection did and did not occur. Outcome data and trough concentrations were recorded from the immediate post-transplant time to over 3 years (656 concentration-effect measures). Seventy one percent of data was obtained after the first 90 days post-transplant. Patients were identified as having experienced hypomagnesemia (20), hypertension (14), hyperkalemia (12), infection (11), nephrotoxicity (8), diarrhea (6), hyperglycemia (3), neurotoxicity(3), and rejection (3) during retrospective follow-up. Median trough concentrations were significantly higher (P <.05) at times patients experienced tacrolimus toxicity compared to no toxicity for nephrotoxicity (11.8 vs. 6.1 ng/mL) and neurotoxicity (15.1 vs. 6.2 ng/mL) and at times when patients suffered from diarrhea (8.9 vs. 6.0 ng/mL). No significant difference could be found between median trough concentrations at which hypertension, hyperkalemia, hyperglycemia, infection and organ rejection did and did not occur. A statistically significant relationship exists between some tacrolimus toxicities and tacrolimus trough concentrations. To minimize toxicity in the later post-transplant period, we propose a target trough tacrolimus concentration of 6 ng/mL.

Cold storage preservation and warm ischaemic injury to isolated arterial segments: endothelial cell injury.

Injury to endothelial cells is thought to be important to the development of the vascular lesion of chronic rejection. It was the aim of this study to develop a semiquantitative method to assess endothelial injury in arterial grafts and to document the injury produced by cold storage preservation and additional warm ischaemia. Twelve- and 24-h cold preservation of rat aortic segments, together with an additional 1 h of warm ischaemia, were assessed. Electron micrographs of representative endothelial cells were scored for cytoplasmic, nuclear and mitochondrial injury. The overall injury score was obtained by addition of the individual scores. Storage for up to 24 h in University of Wisconsin (UW) and Terasaki did not produce any injury. Twenty-four hours of storage in Euro-Collins resulted in endothelial cell death. Injury occurred after 12 h of storage in Ross, Collins and normal saline, and the injury increased following 24 h of storage. One hour of warm ischaemia did not increase the injury. Injury to endothelial cells varies with the preservation solution used and the time of cold storage, so that both the type of solution and the storage time should be taken into account in clinical studies looking at the influence of cold ischaemia time and graft outcome.

Sampling times for monitoring tacrolimus in stable adult liver transplant recipients.

The aim of this study was to determine the most informative sampling time(s) providing a precise prediction of tacrolimus area under the concentration-time curve (AUC). Fifty-four concentration-time profiles of tacrolimus from 31 adult liver transplant recipients were analyzed. Each profile contained 5 tacrolimus whole-blood concentrations (predose and 1, 2, 4, and 6 or 8 hours postdose), measured using liquid chromatography-tandem mass spectrometry. The concentration at 6 hours was interpolated for each profile, and 54 values of AUC(0-6) were calculated using the trapezoidal rule. The best sampling times were then determined using limited sampling strategies and sensitivity analysis. Linear mixed-effects modeling was performed to estimate regression coefficients of equations incorporating each concentration-time point (C0, C1, C2, C4, interpolated C5, and interpolated C6) as a predictor of AUC(0-6). Predictive performance was evaluated by assessment of the mean error (ME) and root mean square error (RMSE). Limited sampling strategy (LSS) equations with C2, C4, and C5 provided similar results for prediction of AUC(0-6) (R2 = 0.869, 0.844, and 0.832, respectively). These 3 time points were superior to C0 in the prediction of AUC. The ME was similar for all time points; the RMSE was smallest for C2, C4, and C5. The highest sensitivity index was determined to be 4.9 hours postdose at steady state, suggesting that this time point provides the most information about the AUC(0-12). The results from limited sampling strategies and sensitivity analysis supported the use of a single blood sample at 5 hours postdose as a predictor of both AUC(0-6) and AUC(0-12). A jackknife procedure was used to evaluate the predictive performance of the model, and this demonstrated that collecting a sample at 5 hours after dosing could be considered as the optimal sampling time for predicting AUC(0-6).

Effect of atorvastatin on cyclosporine pharmacokinetics in liver transplant recipients.

BACKGROUND: The development of hyperlipidemia after liver transplant is frequently treated with hydroxymethylglutaryl coenzyme A reductase inhibitors (statins) such as atorvastatin. As atorvastatin and the primary immunosuppressant drug, cyclosporine, are metabolized by the same pathway, there is the potential for an interaction. OBJECTIVE: To determine the effect of atorvastatin on cyclosporine pharmacokinetics in liver transplant recipients. METHODS: Six stable, long-term adult liver transplant recipients from a single center who developed posttransplant dyslipidemia were recruited to participate in a 14-day, open-label study of atorvastatin 10 mg/d coadministered with standard posttransplant immunosuppression using constant oral doses of cyclosporine and corticosteroids. A 10-point pharmacokinetic profile was performed prior to and on day 14 after commencement of atorvastatin therapy. Cyclosporine concentrations were measured by HPLC-electrospray-tandem mass spectrometry. The AUC was calculated by the linear trapezoidal rule, with other parameters determined by visual inspection. RESULTS: Atorvastatin coadministration increased the cyclosporine AUC by 9% (range 0-20.6%; 3018 vs 3290 ng.h/mL; p = 0.04). No significant change was evident for other cyclosporine pharmacokinetic parameters. Total cholesterol and low-density lipoprotein cholesterol levels were significantly lower on day 14 than at baseline (p < 0.02). One patient developed a twofold increase in transaminases after 2 weeks of atorvastatin therapy, but no other clinical or biochemical adverse events were recorded. CONCLUSIONS: Atorvastatin coadministration increases the cyclosporine AUC by approximately 10% in stable liver transplant recipients. This change in systemic exposure to cyclosporine is of questionable clinical significance. Atorvastatin is effective in reducing cholesterol levels in liver transplant recipients.

Liver transplantation as a therapeutic option for hepatocellular carcinoma.

Better outcomes of the patients receiving liver transplantation for viral hepatitis and hepatocellular carcinoma (HCC) are achieved by improved patient selection and perioperative treatment with antiviral agents including lamivudine, ribavirin and interferon. Patient selection is accomplished by high-quality imaging as well as exclusion of patients with large tumors, obvious extrahepatic disease or macroscopic vascular invasion. Using such criteria, a 5-year survival of 92% has been reached in the Queensland Liver Transplant Service on a small number of highly selected patients with HCC. The treatment algorithm of Makuuchi has guided us in recommending resection, estimating to what extent the liver resection can be performed safely, and timing liver transplantation when it is the only option. Adult-to-adult living-donor liver transplantation is being performed safely in many centers worldwide. The transplantation of liver from living donors to HCC patients, when standard criteria for the likelihood of good outcomes are fulfilled, will increase in Japan in the near future.

The influence of viral genotypes and rejection episodes on the recurrence of hepatitis C after liver transplantation.

PURPOSE: The aim of this study was to report the influence of hepatitis C virus (HCV) genotype and rejection episodes on the outcome of orthotopic liver transplantation (OLT), hepatitis recurrence, and progression to graft cirrhosis after OLT. METHODS: Fifty-three patients who all had undergone OLT for end-stage liver cirrhosis were selected for this study. Hepatitis C genotype was determined. Recurrent hepatitis and rejection were diagnosed based on elevated liver function tests and a liver biopsy. RESULTS: The patients were followed up for a mean of 51.9 +/- 34.3 months. The cumulative survival rate was no different in OLT for hepatitis C and OLT for all other liver diseases. After OLT, serum HCV RNA was detected in 93%. Histological recurrence occurred in 85% of all patients. The 1-, 3-, and 5-year recurrence rates were 48%, 77%, and 85%, respectively. Of the 41 patients with recurrent hepatitis C, 4 (10%) had cirrhosis, 18 (44%) had hepatitis with fibrosis, and 91 (46%) had hepatitis without fibrosis at the end of follow-up. A total of 32% of the patients were infected by HCV genotype 1b and 68% by other HCV genotypes. The recurrence rates were significantly higher in patients infected with genotype 1b than in those with other genotypes ( p = 0.04). Twenty of 48 patients (42%) experienced acute rejection. There was a strong association between the number of rejection episodes and the incidence of HCV-related cirrhosis ( p < 0.01). CONCLUSION: Our findings showed the genotype 1b to result in a higher recurrence rate after OLT. On the other hand, rejection episodes were associated with a more rapid progression to graft cirrhosis.

Increased mononuclear cell activation and apoptosis early after human liver transplantation is associated with a reduced frequency of acute rejection.

Experimental models of orthotopic liver transplantation (OLT) have shown that the very early events post-OLT are critical in distinguishing immunogenic and tolerogenic reactions. In rodents, increased leukocyte apoptosis and cytokine expression have been demonstrated in tolerogenic strain combinations. Information from human OLT recipients is less abundant. The aim of this study was to determine the amount of early leukocyte activation and apoptosis following human OLT, and to correlate this with subsequent rejection status. Peripheral blood mononuclear cells (PBMC) were isolated from 76 patients undergoing OLT - on the day prior, 5 hrs after reperfusion (day 0), and 18-24 hrs post-OLT (day 1). The mean level of apoptotic PBMCs on post OLT day 1 was higher than healthy recipients (0.9% +/- 0.2 vs. 0.2% +/- 0.1, p=0.013). Apoptosis was greater in nonrejecting (NR) (1.1% +/- 0.3) compared with acutely-rejecting (R) (0.3% +/- 0.1, p=0.021) patients. On day 1, PBMC from NR patients had increased expression of IFN-gamma (p=0.006), IL-10 (p=0.016), and CD40 ligand (p=0.02) compared with R. Donor cell chimerism on day 1 did not differ between the groups indicating that this was unlikely to account for increased PBMC apoptosis in the NR group. Interestingly, the level of chimerism on day 0 was significantly higher in NR (3.8% +/- 0.6) compared with R (1.2% +/- 0.4, p=0.004) patients and there was a close correlation between chimerism on day 0 and cytokine expression on day 1. These results imply that similar mechanisms are occurring in the human liver to promote graft acceptance as in the experimental models of liver transplantation and suggest that strategies that promote liver transplant acceptance in rodents might be applicable to humans.