OKT3 prophylaxis in liver transplantation

Maintenance immunosuppression for adults undergoing liver transplantation: a network meta-analysis

BACKGROUND

As part of liver transplantation, immunosuppression (suppressing the host immunity) is given to prevent graft rejections resulting from the immune response of the body against transplanted organ or tissues from a different person whose tissue antigens are not compatible with those of the recipient. The optimal maintenance immunosuppressive regimen after liver transplantation remains uncertain.

OBJECTIVES

To assess the comparative benefits and harms of different maintenance immunosuppressive regimens in adults undergoing liver transplantation through a network meta-analysis and to generate rankings of the different immunosuppressive regimens according to their safety and efficacy.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, Science Citation Index Expanded, World Health Organization International Clinical Trials Registry Platform, and trials registers until October 2016 to identify randomised clinical trials on immunosuppression for liver transplantation.

SELECTION CRITERIA

We included only randomised clinical trials (irrespective of language, blinding, or publication status) in adult participants undergoing liver transplantation (or liver retransplantation) for any reason. We excluded trials in which participants had undergone multivisceral transplantation or participants with established graft rejections. We considered any of the various maintenance immunosuppressive regimens compared with each other.

DATA COLLECTION AND ANALYSIS

We performed a network meta-analysis with OpenBUGS using Bayesian methods and calculated the odds ratio, rate ratio, and hazard ratio (HR) with 95% credible intervals (CrI) based on an available-case analysis, according to National Institute of Health and Care Excellence Decision Support Unit guidance.

MAIN RESULTS

We included a total of 26 trials (3842 participants) in the review, and 23 trials (3693 participants) were included in one or more outcomes in the review. The vast majority of the participants underwent primary liver transplantation. All of the trials were at high risk of bias, and all of the evidence was of low or very low quality. In addition, because of sparse data involving trials at high risk of bias, it is not possible to entirely rely on the results of the network meta-analysis. The trials included mainly participants undergoing primary liver transplantation of varied aetiologies. The follow-up in the trials ranged from 3 to 144 months. The most common maintenance immunosuppression used as a control was tacrolimus. There was no evidence of difference in mortality (21 trials; 3492 participants) or graft loss (15 trials; 2961 participants) at maximal follow-up between the different maintenance immunosuppressive regimens based on the network meta-analysis. In the direct comparison, based on a single trial including 222 participants, tacrolimus plus sirolimus had increased mortality (HR 2.76, 95% CrI 1.30 to 6.69) and graft loss (HR 2.34, 95% CrI 1.28 to 4.61) at maximal follow-up compared with tacrolimus. There was no evidence of differences in the proportion of people with serious adverse events (1 trial; 719 participants), proportion of people with any adverse events (2 trials; 940 participants), renal impairment (8 trials; 2233 participants), chronic kidney disease (1 trial; 100 participants), graft rejections (any) (16 trials; 2726 participants), and graft rejections requiring treatment (5 trials; 1025 participants) between the different immunosuppressive regimens. The network meta-analysis showed that the number of adverse events was lower with cyclosporine A than with many other immunosuppressive regimens (12 trials; 1748 participants), and the risk of retransplantation (13 trials; 1994 participants) was higher with cyclosporine A than with tacrolimus (HR 3.08, 95% CrI 1.13 to 9.90). None of the trials reported number of serious adverse events, health-related quality of life, or costs.

FUNDING

14 trials were funded by pharmaceutical companies who would benefit from the results of the trial; two trials were funded by parties who had no vested interest in the results of the trial; and 10 trials did not report the source of funding.

AUTHORS' CONCLUSIONS

Based on low-quality evidence from a single small trial from direct comparison, tacrolimus plus sirolimus increases mortality and graft loss at maximal follow-up compared with tacrolimus. Based on very low-quality evidence from network meta-analysis, we found no evidence of difference between different immunosuppressive regimens. We found very low-quality evidence from network meta-analysis and low-quality evidence from direct comparison that cyclosporine A causes more retransplantation compared with tacrolimus. Future randomised clinical trials should be adequately powered; performed in people who are generally seen in the clinic rather than in highly selected participants; employ blinding; avoid postrandomisation dropouts or planned cross-overs; and use clinically important outcomes such as mortality, graft loss, renal impairment, chronic kidney disease, and retransplantation. Such trials should use tacrolimus as one of the control groups. Moreover, such trials ought to be designed in such a way as to ensure low risk of bias and low risks of random errors.

Antibody induction versus placebo, no induction, or another type of antibody induction for liver transplant recipients

BACKGROUND

Liver transplantation is an established treatment option for end-stage liver failure. To date, no consensus has been reached on the use of immunosuppressive T-cell antibody induction for preventing rejection after liver transplantation.

OBJECTIVES

To assess the benefits and harms of immunosuppressive T-cell specific antibody induction compared with placebo, no induction, or another type of T-cell specific antibody induction for prevention of acute rejection in liver transplant recipients.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Science Citation Index Expanded, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) until September 2013.

SELECTION CRITERIA

Randomised clinical trials assessing immunosuppression with T-cell specific antibody induction compared with placebo, no induction, or another type of antibody induction in liver transplant recipients. Our inclusion criteria stated that participants within each included trial should have received the same maintenance immunosuppressive therapy. We planned to include trials with all of the different types of T-cell specific antibodies that are or have been used for induction (ie., polyclonal antibodies (rabbit of horse antithymocyte globulin (ATG), or antilymphocyte globulin (ALG)), monoclonal antibodies (muromonab-CD3, anti-CD2, or alemtuzumab), and interleukin-2 receptor antagonists (daclizumab, basiliximab, BT563, or Lo-Tact-1)).

DATA COLLECTION AND ANALYSIS

We used RevMan analysis for statistical analysis of dichotomous data with risk ratio (RR) and of continuous data with mean difference (MD), both with 95% confidence intervals (CIs). We assessed the risk of systematic errors (bias) using bias risk domains with definitions. We used trial sequential analysis to control for random errors (play of chance). We presented outcome results in a summary of findings table.

MAIN RESULTS

We included 19 randomised clinical trials with a total of 2067 liver transplant recipients. All 19 trials were with high risk of bias. Of the 19 trials, 16 trials were two-arm trials, and three trials were three-arm trials. Hence, we found 25 trial comparisons with antibody induction agents: interleukin-2 receptor antagonist (IL-2 RA) versus no induction (10 trials with 1454 participants); monoclonal antibody versus no induction (five trials with 398 participants); polyclonal antibody versus no induction (three trials with 145 participants); IL-2 RA versus monoclonal antibody (one trial with 87 participants); and IL-2 RA versus polyclonal antibody (two trials with 112 participants). Thus, we were able to compare T-cell specific antibody induction versus no induction (17 trials with a total of 1955 participants). Overall, no difference in mortality (RR 0.91; 95% CI 0.64 to 1.28; low-quality of evidence), graft loss including death (RR 0.92; 95% CI 0.71 to 1.19; low-quality of evidence), and adverse events ((RR 0.97; 95% CI 0.93 to 1.02; low-quality evidence) outcomes was observed between any kind of T-cell specific antibody induction compared with no induction when the T-cell specific antibody induction agents were analysed together or separately. Acute rejection seemed to be reduced when any kind of T-cell specific antibody induction was compared with no induction (RR 0.85, 95% CI 0.75 to 0.96; moderate-quality evidence), and when trial sequential analysis was applied, the trial sequential monitoring boundary for benefit was crossed before the required information size was obtained. Furthermore, serum creatinine was statistically significantly higher when T-cell specific antibody induction was compared with no induction (MD 3.77 μmol/L, 95% CI 0.33 to 7.21; low-quality evidence), as well as when polyclonal T-cell specific antibody induction was compared with no induction, but this small difference was not clinically significant. We found no statistically significant differences for any of the remaining predefined outcomes - infection, cytomegalovirus infection, hepatitis C recurrence, malignancy, post-transplant lymphoproliferative disease, renal failure requiring dialysis, hyperlipidaemia, diabetes mellitus, and hypertension - when the T-cell specific antibody induction agents were analysed together or separately. Limited data were available for meta-analysis on drug-specific adverse events such as haematological adverse events for antithymocyte globulin. No data were found on quality of life.When T-cell specific antibody induction agents were compared with another type of antibody induction, no statistically significant differences were found for mortality, graft loss, and acute rejection for the separate analyses. When interleukin-2 receptor antagonists were compared with polyclonal T-cell specific antibody induction, drug-related adverse events were less common among participants treated with interleukin-2 receptor antagonists (RR 0.23, 95% CI 0.09 to 0.63; low-quality evidence), but this was caused by the results from one trial, and trial sequential analysis could not exclude random errors. We found no statistically significant differences for any of the remaining predefined outcomes: infection, cytomegalovirus infection, hepatitis C recurrence, malignancy, post-transplant lymphoproliferative disease, renal failure requiring dialysis, hyperlipidaemia, diabetes mellitus, and hypertension. No data were found on quality of life.

AUTHORS' CONCLUSIONS

The effects of T-cell antibody induction remain uncertain because of the high risk of bias of the randomised clinical trials, the small number of randomised clinical trials reported, and the limited numbers of participants and outcomes in the trials. T-cell specific antibody induction seems to reduce acute rejection when compared with no induction. No other clear benefits or harms were associated with the use of any kind of T-cell specific antibody induction compared with no induction, or when compared with another type of T-cell specific antibody. Hence, more randomised clinical trials are needed to assess the benefits and harms of T-cell specific antibody induction compared with placebo, and compared with another type of antibody, for prevention of rejection in liver transplant recipients. Such trials ought to be conducted with low risks of systematic error (bias) and low risk of random error (play of chance).

Antibody induction versus corticosteroid induction for liver transplant recipients

BACKGROUND

Liver transplantation is an established treatment option for end-stage liver failure. To date, no consensus has been reached on the use of immunosuppressive T-cell specific antibody induction compared with corticosteroid induction of immunosuppression after liver transplantation.

OBJECTIVES

To assess the benefits and harms of T-cell specific antibody induction versus corticosteroid induction for prevention of acute rejection in liver transplant recipients.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Science Citation Index Expanded, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) on 30 September 2013 together with reference checking, citation searching, contact with trial authors and pharmaceutical companies to identify additional trials.

SELECTION CRITERIA

We included all randomised clinical trials assessing immunosuppression with T-cell specific antibody induction versus corticosteroid induction in liver transplant recipients. Our inclusion criteria stated that participants within each included trial should have received the same maintenance immunosuppressive therapy.

DATA COLLECTION AND ANALYSIS

We used RevMan for statistical analysis of dichotomous data with risk ratio (RR) and of continuous data with mean difference (MD), both with 95% confidence intervals (CIs). We assessed risk of systematic errors (bias) using bias risk domains with definitions. We used trial sequential analysis to control for random errors (play of chance).

MAIN RESULTS

We included 10 randomised trials with a total of 1589 liver transplant recipients, which studied the use of T-cell specific antibody induction versus corticosteroid induction. All trials were with high risk of bias. We compared any kind of T-cell specific antibody induction versus corticosteroid induction in 10 trials with 1589 participants, including interleukin-2 receptor antagonist induction versus corticosteroid induction in nine trials with 1470 participants, and polyclonal T-cell specific antibody induction versus corticosteroid induction in one trial with 119 participants.Our analyses showed no significant differences regarding mortality (RR 1.01, 95% CI 0.72 to 1.43), graft loss (RR 1.12, 95% CI 0.82 to 1.53) and acute rejection (RR 0.84, 95% CI 0.70 to 1.00), infection (RR 0.96, 95% CI 0.85 to 1.09), hepatitis C virus recurrence (RR 0.89, 95% CI 0.79 to 1.00), malignancy (RR 0.59, 95% CI 0.13 to 2.73), and post-transplantation lymphoproliferative disorder (RR 1.00, 95% CI 0.07 to 15.38) when any kind of T-cell specific antibody induction was compared with corticosteroid induction (all low-quality evidence). Cytomegalovirus infection was less frequent in patients receiving any kind of T-cell specific antibody induction compared with corticosteroid induction (RR 0.50, 95% CI 0.33 to 0.75; low-quality evidence). This was also observed when interleukin-2 receptor antagonist induction was compared with corticosteroid induction (RR 0.55, 95% CI 0.37 to 0.83; low-quality evidence), and when polyclonal T-cell specific antibody induction was compared with corticosteroid induction (RR 0.21, 95% CI 0.06 to 0.70; low-quality evidence). However, when trial sequential analysis regarding cytomegalovirus infection was applied, the required information size was not reached. Furthermore, diabetes mellitus occurred less frequently when T-cell specific antibody induction was compared with corticosteroid induction (RR 0.45, 95% CI 0.34 to 0.60; low-quality evidence), when interleukin-2 receptor antagonist induction was compared with corticosteroid induction (RR 0.45, 95% CI 0.35 to 0.61; low-quality evidence), and when polyclonal T-cell specific antibody induction was compared with corticosteroid induction (RR 0.12, 95% CI 0.02 to 0.95; low-quality evidence). When trial sequential analysis was applied, the trial sequential monitoring boundary for benefit was crossed. We found no subgroup differences for type of interleukin-2 receptor antagonist (basiliximab versus daclizumab). Four trials reported on adverse events. However, no differences between trial groups were noted. Limited data were available for meta-analysis on drug-specific adverse events such as haematological adverse events for antithymocyte globulin. No data were available on quality of life.

AUTHORS' CONCLUSIONS

Because of the low quality of the evidence, the effects of T-cell antibody induction remain uncertain. T-cell specific antibody induction seems to reduce diabetes mellitus and may reduce cytomegalovirus infection when compared with corticosteroid induction. No other clear benefits or harms were associated with the use of T-cell specific antibody induction compared with corticosteroid induction. For some analyses, the number of trials investigating the use of T-cell specific antibody induction after liver transplantation is small, and the numbers of participants and outcomes in these randomised trials are limited. Furthermore, the included trials are heterogeneous in nature and have applied different types of T-cell specific antibody induction therapy. All trials were at high risk of bias. Hence, additional randomised clinical trials are needed to assess the benefits and harms of T-cell specific antibody induction compared with corticosteroid induction for liver transplant recipients. Such trials ought to be conducted with low risks of systematic error and of random error.

Induction immunosuppression

Induction immunosuppression is intense, prophylactic therapy used at the time of transplantation based on the empiric observation that more powerful immunosuppression is required to prevent acute rejection early. In the past decade, there has been a growing trend towards the use of specialized agents such as antibody therapies for induction. In general, these agents have been shown to reduce the rate of acute rejection. However, their use has not been clearly shown to improve long-term transplant outcomes. This overview will review the biological basis for induction immunosuppression and the mechanisms of action of those specialized induction agents currently in clinical use. Clinical trials investigating induction regimens will be evaluated, and an individualized approach to the use of induction immunosuppressants will be presented.

Induction immunosuppression with rabbit antithymocyte globulin in pediatric liver transplantation

Routine use of rabbit antithymocyte globulin (RATG) induction therapy remains controversial in pediatric liver transplantation. We reviewed our experience of 18 cadaveric liver transplants in 18 children over a span of 2 years. All patients received the same immunosuppression: perioperative steroid therapy with taper, 3 doses of RATG, and maintenance therapy of steroids and tacrolimus started on postoperative day 3. Mean follow-up was 2.2 +/- 0.2 years. End-stage liver disease was secondary to biliary atresia in 10 patients (56%) and metabolic disorders in 4 patients (22%). Graft and patient survival were 89%. Serum bilirubin was 1.2 mg/dL, 1.1 mg/dL, 0.5 mg/dL, and 0.5 mg/dL at 1, 3, 6, and 12 months, respectively. The 2 mortalities were secondary to multiple organ system failure. Overall rejection rate was 17% (3/18). Rejection episodes occurred at 4, 6, and 7 months. Two patients were treated with steroids; the third was treated with OKT3. No patient has developed posttransplant lymphoproliferative disease. Serum creatinine was 0.7 mg/dL, 0.6 mg/dL, 0.6 mg/dL, and 0.6 mg/dL at 1, 3, 6, and 12 months, respectively, among surviving patients. In conclusion, our data suggest that RATG induction with steroid and tacrolimus maintenance therapy is safe, easy to use, and effective in the prevention of rejection.

Modern immunosuppression

The current treatment of posttransplant lymphoproliferative disease (PTLD) includes prophylaxis at the time of transplant, decreasing or stopping immunosuppresion and initiation of antiviral therapy in patients with polymerase chain reaction or clinical evidence of PTLD, and judicial reintroduction of immunosuppression in patients who have cleared their PTLD and have begun to have rejection. The pharmacology, pharmacokinetics, notable side effects, and toxicities of the immunosuppressive agents are described in this article. At the conclusion of each section the author's current practice with these agents and treatment strategies are described.

Cytokine profiles in early rejection following OKT3 treatment in liver transplant patients

OKT3 , a murine monoclonal antibody specific to the human CD3 complex, induces immunosuppression by depletion of T cells. Administration of OKT3 results in significant release of proinflammatory cytokines, such as TNFalpha and IL1beta. Liver recipients who experience rejection within 3 weeks after transplantation with OKT3 prophylaxis recover their T cells by postoperative day 10 despite complete initial clearance. We sought to analyze the role of proinflammatory and Th-1 cytokines in T cell recovery and rejection after liver transplantation with OKT3 prophylaxis. In plasma samples from 32 patients, we measured TNFalpha, IL1beta and IL6 (before transplant and on postoperative days 1, 2 and 3) and IL2, IFNgamma, sIL2R and slCAM (postoperative days 5, 7 and 10) and examined possible correlations with T-cell recovery and occurrence of rejection within 3 weeks. TNFalpha, IL1beta, and IL6 did not correlate with T-cell recovery. In patients who rejected, IL2 and IFNgamma on postoperative days 5 and 7 correlated with degree of T-cell recovery by day 10; a significant rise in sIL2R over time also correlated with T-cell recovery in this group. Our results emphasize the role of Th-1 cytokines in rejection following OKT3 induction and suggest that markers of T cell activation may predict risk.

Use of low-dose OKT3 as induction therapy in liver transplantation

BACKGROUND

A pilot study was performed to prospectively evaluate the safety and efficacy of "low-dose" OKT3 induction after liver transplantation.

METHODS

Sixteen patients received a 5- to 10-day course of OKT3 (2.5 mg i.v. daily) along with azathioprine, prednisone, and the delayed introduction of cyclosporine (Neoral).

RESULTS

Patient and graft survival rates at 1 year were 88% and 82%. Five patients (31%) had biopsy-proven rejection; all five were treated successfully with steroids. There were 15 infections in 12 patients, including 5 cytomegalovirus infections. Adverse events attributed to OKT3 consisted of low-grade fever (five patients), transient hypoxemia (three patients), and transient hypotension (two patients). Pharmacy acquisition costs for OKT3 averaged $2,139 less as compared to a group of historical controls receiving full-dose therapy.

CONCLUSIONS

Low-dose OKT3 induction appears to be a safe and useful method of postoperative immunosuppression after liver transplantation. Its ultimate clinical, immunologic, and economic efficacy awaits determination by randomized trial.

Artificial liver support: the pipe dream of today should be the reality of the near future

The title of this article is taken from an interesting Letter to the Editor entitled 'Artificial liver support-Pipe dream or reality' by Cattral and Levy of the Toronto Hospital, Canada, published in the New England Journal of Medicine 1994, in which the authors persuasively propose possibilities of artificial liver support and suggest its advantages. We find that their suggestions agree with the core of our thoughts on this subject. The present article deals with the concept of implanting livers taken from humans, primates or non-primates (e.g. hog) into patients in parallel with their own metabolically fatigued or cirrhotic livers, with minimal surgical manipulation, as a prelude to total artificial liver support via a liver dialysis device. While the possibility exists that the host liver may recover function, a donor liver, whether implanted into the patient's abdomen or connected in vitro to the patient's circulatory system extracorporeally, may provide the host liver respite and a period for recovery and proliferation, if possible. Once recovery is under way, the donor liver may be removed and the patient will not experience the usual risks of rejection and the necessary side-effects of immunosuppression associated with conventional full hepatectomy and donor transplantation. The viability of a liver implantation model in rats is correlated in this article with hepatic acute phase response.

Muromonab CD3: a reappraisal of its pharmacology and use as prophylaxis of solid organ transplant rejection

The murine monoclonal antibody muromonab CD3 (OKT3) is directed against the CD3 antigen on peripheral human T cells and effectively blocks all T cell function. Prophylaxis with muromonab CD3 (5mg intravenously once daily for 10 to 14 days) as induction therapy together with corticosteroids, azathioprine and delayed cyclosporin (sequential therapy) optimises early graft function by delaying the potentially nephrotoxic and hepatotoxic effects of cyclosporin until graft function is established. Although clinical data are limited (by inconsistencies in trial design and trial size), prophylactic muromonab CD3-based sequential therapy is significantly more effective than standard triple therapy in the prophylaxis of allograft rejection in renal and hepatic, but not cardiac, transplant recipients. Benefits are particularly notable in patients with delayed graft function. No significant between-treatment differences in patient survival have been observed. The overall efficacy of muromonab CD3- and polyclonal-based prophylactic regimens appears to be similar, although results vary between investigators and confirmation is needed. An anti-interleukin-2 monoclonal antibody-based prophylactic regimen improved graft and patient survival compared with muromonab CD3-based prophylaxis in hepatic transplant recipients. Antimuromonab CD3 antibodies may develop; however, muromonab CD3 may be successfully reused in patients with low titres. Preliminary pharmacoeconomic data suggest that mean drug costs are greater with quadruple immunosuppressive regimens containing muromonab CD3, antithymocyte globulin (ATG) or antilymphocyte globulin (ALG) than with triple therapy. Drug costs with prophylactic muromonab CD3-based regimens were similar or greater than those with polyclonal-based protocols. The first doses of muromonab CD3 are associated with the 'cytokine-release syndrome'. More severe first-dose events include aseptic meningitis, intragraft thromboses, seizures and potentially fatal pulmonary oedema. The incidence and/or severity of cytomegalovirus infection with prophylactic muromonab CD3 based immunosuppression is similar to or greater than that with triple therapy and ATG- or ALG-based regimens. However, the risk of infection and also the observed increase in lymphoproliferative disorders appears to be related to the degree of immunosuppression rather than to the drug itself Thus, sequential muromonab CD3-based therapy is more effective than standard triple therapy (in renal and hepatic transplant recipients) and appears to be similar to that of polyclonal-based regimens in the prophylaxis of transplant rejection. Although the routine use of prophylactic muromonab CD3 in low-risk patients with primary graft function does not appear to be justified, prophylactic muromonab CD3-based therapy has a role in patients at high risk of rejection.

Renal dysfunction associated with liver transplantation

It has been known for some time that a variety of liver diseases affect kidney function, but renal dysfunction associated with orthotopic liver transplantation has received scant attention. Although the mechanisms mediating these abnormalities are incompletely defined, advances in the understanding of renal pathophysiology after liver transplantation have made it possible to develop new treatment strategies. Aggressive and early intervention to diagnose and treat renal complications associated with liver transplantation should be the goal for transplant centres.

Hepatic allograft rejection: new developments in terminology, diagnosis, prevention, and treatment

Hepatic allograft rejection remains a major cause of morbidity related to the need for increased immunosuppression and continues to be a principal cause of late failure of the graft. Hepatic allograft rejection is defined on the basis of morphologic findings; cellular rejection is defined as portal or periportal hepatitis with nonsuppurative cholangitis or endotheliitis (or both), and ductopenic rejection is defined as loss of interlobular and septal bile ducts, typically in at least 50% of the portal tracts. The overall incidence of episodes of cellular rejection, which usually occur within the first 2 weeks after liver transplantation, varies from 50 to 100%. Ductopenic rejection occurs in approximately 8% of patients who undergo initial liver transplantation and is usually diagnosed between 6 weeks and 6 months after transplantation. Induction and maintenance immunosuppression with triple-drug (cyclosporine, prednisone, and azathioprine) therapy and other combinations that include antilymphocyte preparations, however, has decreased the incidence of both cellular and ductopenic rejection. In patients experiencing episodes of cellular rejection, high-dose intravenously administered corticosteroid therapy yields the best response and is associated with a lower incidence of ductopenic rejection than is low-dose and orally administered corticosteroid therapy. The correlation between degree of biochemical liver dysfunction and presence of histologic rejection is minimal early after transplantation. Histologic severity of rejection, however, suggests which patients will require more immunosuppression and which patients may need antilymphocyte therapy for controlling the rejection episode. With the availability of new immunosuppressive agents, distinguishing patients at high risk for rejection is important. The goals for use of new immunosuppressive agents and regimens are to improve graft and patient survival, to decrease the incidence of cellular and ductopenic rejection, and to minimize side effects and complications.