Kidney transplantation with rabbit antithymocyte globulin induction and sirolimus monotherapy

Immunomodulation of T cell-mediated alloimmunity by proximity to endothelial cells under the mammalian target of rapamycin blockade

Endothelial cells (ECs) are an initial barrier between vascularized organ allografts and the host immune system and are thus well positioned to initiate and influence alloimmune rejection. The mammalian target of rapamycin inhibitor rapamycin is known to inhibit T cell activation and attenuate acute allograft rejection. It also has numerous effects on ECs. We hypothesized that A mammalian target of rapamycin blockade might directly alter EC alloimmunogenicity and reduce alloimmune responses independent of its effects on T cell function. Here we report that rapamycin treatment modulates EC coinhibitory ligand expression and alters cytokine/chemokine production. It alters the EC transcriptome broadly associated with negative regulation of immune responses. Rapamycin-treated ECs suppress EC-specific T cell proliferation independent of programmed cell death 1/programmed death-ligand interaction and inhibit T cells responding to adjacent allogeneic cells in a contact-independent manner via secreted inhibitory mediators above 10 kDa. The T cell hyporesponsiveness induced by rapamycin-pretreated ECs was rescued by exogenous interleukin 2. Preexposing donor hearts to rapamycin improves the effect of B7 costimulation blockade in prolonging heart allograft survival in a major histocompatibility complex-mismatched mouse model. Our results indicate that rapamycin-treated ECs have reduced alloimmunogenicity and created a local, contact-independent environment that limits T cell alloreactivity via anergy induction and improves the efficacy of B7 costimulation blockade.

Pretransplant, Th17 dominant alloreactivity in highly sensitized kidney transplant candidates

Introduction

Sensitization to donor human leukocyte antigen (HLA) molecules prior to transplantation is a significant risk factor for delayed access to transplantation and to long-term outcomes. Memory T cells and their cytokines play a pivotal role in shaping immune responses, thereby increasing the risk of allograft rejection among highly sensitized patients. This study aims to elucidate the precise contribution of different CD4+ memory T cell subsets to alloreactivity in highly sensitized (HS) kidney transplant recipients.

Methods and results

Stimulation of peripheral blood mononuclear cells (PBMC) with various polyclonal stimulating agents to assess non-specific immune responses revealed that HS patients exhibit elevated immune reactivity even before kidney transplantation, compared to non-sensitized (NS) patients. HS patients' PBMC displayed higher frequencies of CD4+ T cells expressing IFNγ, IL4, IL6, IL17A, and TNFα and secreted relatively higher levels of IL17A and IL21 upon stimulation with PMA/ionomycin. Additionally, PBMC from HS patients stimulated with T cell stimulating agent phytohemagglutinin (PHA) exhibited elevated expression levels of IFNγ, IL4 and, IL21. On the other hand, stimulation with a combination of resiquimod (R848) and IL2 for the activation of memory B cells demonstrated higher expression of IL17A, TNFα and IL21, as determined by quantitative real-time PCR. A mixed leukocyte reaction (MLR) assay, employing third-party donor antigen presenting cells (APCs), was implemented to evaluate the direct alloreactive response. HS patients demonstrated notably higher frequencies of CD4+ T cells expressing IL4, IL6 and IL17A. Interestingly, APCs expressing recall HLA antigens triggered a stronger Th17 response compared to APCs lacking recall HLA antigens in sensitized patients. Furthermore, donor APCs induced higher activation of effector memory T cells in HS patients as compared to NS patients.

Conclusion

These results provide an assessment of pretransplant alloreactive T cell subsets in highly sensitized patients and emphasize the significance of Th17 cells in alloimmune responses. These findings hold promise for the development of treatment strategies tailored to sensitized kidney transplant recipients, with potential clinical implications.

Age-related effects on thymic output and homeostatic T cell expansion following depletional induction in renal transplant recipients

Thymic output and homeostatic mature cell proliferation both influence T cell repopulation following depletional induction, though the relative contribution of each and their association with recipient age have not been well studied. We investigated the repopulating T cell kinetics in kidney transplant recipients who underwent alemtuzumab induction followed by belatacept/rapamycin-based immunosuppression over 36-month posttransplantation. We focused specifically on the correlation between repopulating T cell subsets and the age of patients. Substantial homeostatic Ki67-expressing T cell proliferation was seen posttransplantation. A repertoire enriched for naïve T (T_Naïve ) cells emerged posttransplantation. Analysis by generalized estimating equation linear models revealed a strong negative linear association between reconstituting T_Naïve cells and advancing age. A relationship between age and persistence of effector memory cells was shown. We assessed thymic output and found an increase in the frequency of recent thymic emigrants (RTEs, CD4⁺ CD31⁺ ) at 12-month posttransplantation. Patients under 30 years of age showed significantly higher levels of CD4⁺ CD31⁺ cells than patients over 55 years of age pre- and posttransplantation. IL-7 and autologous mature dendritic cells (mDCs) induced CD57^- cell proliferation. In contrast, mDCs, but not IL-7, induced CD57⁺ cell proliferation. This study establishes the relationship between age and thymic output during T cell homeostatic repopulation after alemtuzumab induction. Trial Registration: ClinicalTrials.gov - NCT00565773.

Kidney transplantation using alemtuzumab, belatacept, and sirolimus: Five-year follow-up

Kidney transplant outcomes are limited by toxicities associated with calcineurin inhibitors and steroids. This trial was conducted to determine whether a costimulation blockade (CoB)-based regimen could achieve acceptable long-term outcomes and graft survival could be maintained solely with CoB. Forty patients underwent alemtuzumab induction followed by belatacept and sirolimus maintenance therapy. Patients were offered weaning to belatacept monotherapy after 1 year and followed for 5 years. Five-year patient and graft survival rates were 100% and 95%, respectively. Graft function remained stable with a mean estimated glomerular filtration rates of 67 ± 21 and 71 ± 19 at 36 and 60 months, respectively. There was no clinical rejection in the first year; subclinical rejection was detected by protocol biopsy in 4 patients. Twelve patients were successfully weaned to belatacept monotherapy. Cytomegalovirus and Epstein-Barr virus reactivations were well controlled, but 9 patients experienced transient BK viremia during the first year. Alemtuzumab produced profound lymphopenia followed by gradual T cell and more rapid B cell reconstitution to a repertoire deviated toward naïve cells with increased regulatory T cells. This regimen effectively prevents allograft rejection without using steroids or calcineurin inhibitors, enriches for naïve cells susceptible to control with CoB, and permits control of rejection with belatacept monotherapy in selected patients.

B cell reconstitution following alemtuzumab induction under a belatacept-based maintenance regimen

Lymphocyte depletion has been shown to control costimulation blockade-resistant rejection but, in some settings, to exacerbate antibody-mediated rejection (AMR). We have used alemtuzumab, which depletes T and B cells, combined with belatacept and rapamycin and previously reported control of both costimulation blockade-resistant rejection and AMR. To evaluate this regimen's effect on B cell signatures, we investigated 40 patients undergoing this therapy. B cell counts and phenotypes were interrogated using flow cytometry, and serum was analyzed for total IgG, IgM, and donor-specific alloantibody (DSA). Alemtuzumab induction produced pan-lymphocyte depletion; B cells repopulated faster and more completely than T cells. Reconstituting B cells were predominantly naïve, and memory B cells were significantly reduced (P = .001) post repopulation. Two B cell populations with potential immunomodulatory effects-regulatory (CD38^hi CD24^hi IgM^hi CD20^hi ) and transitional B cells (CD19⁺ CD27^- IgD⁺ CD38^hi )-were enriched posttransplant (P = .001). Total serum IgG decreased from baseline (P = .016) while IgM levels remained stable. Five patients developed DSAs within 36 months posttransplant, but none developed AMR. Baseline IgG levels in these patients were significantly higher than those in patients without DSAs. These findings suggest that belatacept and rapamycin together limit homeostatic B cell activation following B cell depletion and may lessen the risk of AMR. This regimen warrants prospective, comparative study. ClinicalTrials.gov NCT00565773.

IL-21 Biased Alemtuzumab Induced Chronic Antibody-Mediated Rejection Is Reversed by LFA-1 Costimulation Blockade

Despite its excellent efficacy in controlling T cell mediated acute rejection, lymphocyte depletion may promote a humoral response. While T cell repopulation after depletion has been evaluated in many aspects, the B cell response has not been fully elucidated. We tested the hypothesis that the mechanisms also involve skewed T helper phenotype after lymphocytic depletion. Post-transplant immune response was measured from alemtuzumab treated hCD52Tg cardiac allograft recipients with or without anti-LFA-1 mAb. Alemtuzumab induction promoted serum DSA, allo-B cells, and CAV in humanized CD52 transgenic (hCD52Tg) mice after heterotopic heart transplantation. Additional anti-LFA-1 mAb treatment resulted in reduced DSA (Fold increase 4.75 ± 6.9 vs. 0.7 ± 0.5; p < 0.01), allo-specific B cells (0.07 ± 0.06 vs. 0.006 ± 0.002 %; p < 0.01), neo-intimal hyperplasia (56 ± 14% vs. 23 ± 13%; p < 0.05), arterial disease (77.8 ± 14.2 vs. 25.8 ± 20.1%; p < 0.05), and fibrosis (15 ± 23.3 vs. 4.3 ± 1.65%; p < 0.05) in this alemtuzumab-induced chronic antibody-mediated rejection (CAMR) model. Surprisingly, elevated serum IL-21 levels in alemtuzumab-treated mice was reduced with LFA-1 blockade. In accordance with the increased serum IL-21 level, alemtuzumab treated mice showed hyperplastic germinal center (GC) development, while the supplemental anti-LFA-1 mAb significantly reduced the GC frequency and size. We report that the incomplete T cell depletion inside of the GC leads to a systemic IL-21 dominant milieu with hyperplastic GC formation and CAMR. Conventional immunosuppression, such as tacrolimus and rapamycin, failed to reverse AMR, while co-stimulation blockade with LFA-1 corrected the GC hyperplastic response. The identification of IL-21 driven chronic AMR elucidates a novel mechanism that suggests a therapeutic approach with cytolytic induction.

Drug-Induced Hematological Cytopenia in Kidney Transplantation and the Challenges It Poses for Kidney Transplant Physicians

Drug-induced hematological cytopenia is common in kidney transplantation. Various cytopenia including leucopenia (neutropenia), thrombocytopenia, and anemia can occur in kidney transplant recipients. Persistent severe leucopenia or neutropenia can lead to opportunistic infections of various etiologies. On the contrary, reducing or stopping immunosuppressive medications in these events can provoke a rejection. Transplant clinicians are often faced with the delicate dilemma of balancing cytopenia and rejection from adjustments of immunosuppressive regimen. Differentials of drug-induced cytopenia are wide. Identification of culprit medication and subsequent modification is also challenging. In this review, we will discuss individual drug implicated in causing cytopenia and correlate it with corresponding literature evidence.

Current challenges and future directions for liver transplantation

Liver transplantation is an effective and widely used therapy for several patients with acute and chronic liver diseases. The discrepancy between the number of patients on the waiting list and available donors remains the key issue and is responsible for the high rate of waiting list mortality. The recent news is that the majority of patients with hepatitis C virus related liver disease will be cured by new antivirals therefore we should expect soon a reduction in the need of liver transplantation for these recipients. This review aims to highlight, in two different sections, the main open issues of liver transplantation concerning the current and future strategies to the best use of limited number of organs. The first section cover the strategies to increase the donor pool, discussing the use of older donors, split grafts, living donation and donation after cardiac death and mechanical perfusion systems to improve the preservation of organs before liver transplantation. Challenges in immunosuppressive therapy and operational tolerance induction will be evaluated as potential tools to increase the survival in liver transplant recipients and to reducing the need of re-transplantation. The second section is devoted to the evaluation of possible new indications to liver transplantation, where the availability of organs by implementing the strategies mentioned in the first section and the reduction in the number of waiting transplants for HCV disease is realized. Among these new potential indications for transplantation, the expansion of the Milan criteria for hepatocellular cancer is certainly the most open to question.

Strategies to Prevent Chronic Allograft Nephropathy in Kidney Transplantation: Focus on Calcineurin Inhibitors

Chronic allograft nephropathy is one of the leading causes of long-term graft failure in kidney transplant recipients. The etiology of this condition is multifactorial, but administration of calcineurin inhibitors is often implicated. With the introduction of newer immunosuppressive agents, strategies for calcineurin inhibitor minimization, avoidance, and withdrawal have been emerging in the literature. These strategies may improve long-term kidney allograft function, but are not without risks. Results from recent clinical trials evaluating the safety and efficacy of these strategies to prevent chronic allograft nephropathy in kidney transplant recipients are summarized and reviewed. Patients who had never received a calcineurin inhibitor or who had cyclosporine withdrawn from their regimens had better kidney function than patients who received or kept receiving a calcineurin inhibitor. The impact of the improvement in kidney function on long-term graft survival remains to be determined. In addition, the benefit in renal function must be weighed against the bone marrow toxicities and/or metabolic complications associated with these regimens.

Alemtuzumab as Antirejection Therapy: T Cell Repopulation and Cytokine Responsiveness

Supplemental digital content is available in the text.

Background

Alemtuzumab induction therapy in kidney transplant patients results in T cell depletion followed by slow immune reconstitution of memory T cells with reduced immune functions. The kinetics and functional characteristics of T cell reconstitution when alemtuzumab is given during immune activation, ie, as antirejection therapy, are unknown.

Methods

Patients (n = 12) with glucocorticoid-resistant or severe vascular kidney transplant rejection were treated with alemtuzumab. Flow cytometric analysis was performed on whole blood to measure cell division by the marker Ki-67, and cytokine responsiveness by IL-2–mediated and IL-7–mediated phosphorylation of signal transducer and activator of transcription 5 of T cells before and during the first year after rejection therapy.

Results

At 1 year after alemtuzumab antirejection therapy, the total T cell population recovered to baseline level. Repopulation of CD4+ and CD8+ T cells was associated with increased percentages of Ki-67+ proliferating T cells (P < 0.05). In addition, both populations showed a phenotypic shift toward relatively more memory T cells (P < 0.01). At the functional level, IL-7 reactivity of CD4+ memory T cells was diminished, reflected by a decreased capacity to phosphorylate signal transducer and activator of transcription 5 during the first 6 months after alemtuzumab treatment (P < 0.05), whereas reactivity to IL-2 was preserved. CD8+ T cells were affected in terms of both IL-2 and IL-7 responses (both P < 0.05). After reconstitution, relatively more regulatory T cells were present, and a relatively high proportion of Ki-67+ T cells was observed.

Conclusions

Preliminary data from this small series suggest that alemtuzumab antirejection therapy induces homeostatic proliferation of memory and regulatory T cells with diminished responsiveness to the homeostatic cytokine IL-7. IL-2 responsiveness was affected in repopulated CD8+ T cells.

T cells Exhibit Reduced Signal Transducer and Activator of Transcription 5 Phosphorylation and Upregulated Coinhibitory Molecule Expression After Kidney Transplantation

BACKGROUND

T-cell depletion therapy is associated with diminished interleukin (IL)-7/IL-15-dependent homeostatic proliferation resulting in incomplete T-cell repopulation. Furthermore, it is associated with impaired T-cell functions. We hypothesized that this is the result of impaired cytokine responsiveness of T cells, through affected signal transducer and activator of transcription (STAT)5 phosphorylation and upregulation of coinhibitory molecules.

MATERIALS AND METHODS

Patients were treated with T cell-depleting rabbit antithymocyte globulin (rATG) (6 mg/kg, n = 17) or nondepleting, anti-CD25 antibody (basiliximab, 2 × 40 mg, n = 25) induction therapy, in combination with tacrolimus, mycophenolate mofetil, and steroids. Before and the first year after transplantation, IL-7 and IL-2 induced STAT5 phosphorylation, and the expression of the coinhibitory molecules programmed cell death protein 1 (PD-1), T cell immunoglobulin mucin-3 (TIM-3), lymphocyte activation gene-3 (LAG-3), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), cluster of differentiation (CD) 160, and CD244 was measured by flow cytometry.

RESULTS

The first year after rATG, CD4+, and CD8+ T cells were affected in their IL-7-dependent phosphorylation of STAT5 (pSTAT5) which was most outspoken in the CD8+ memory population. The capacity of CD4+ and CD8+ T cells to pSTAT5 in response to IL-2 decreased after both rATG and basiliximab therapy. After kidney transplantation, the percentage of TIM-3+, PD-1+, and CD160+CD4+ T cells and the percentage of CD160+ and CD244+CD8+ T cells increased, with no differences in expression between rATG- and basiliximab-treated patients. The decrease in pSTAT5 capacity CD8+ T cells and the increase in coinhibitory molecules were correlated.

CONCLUSIONS

We show that memory T cells in kidney transplant patients, in particular after rATG treatment, have decreased cytokine responsiveness by impaired phosphorylation of STAT5 and have increased expression of coinhibitory molecules, processes which were correlated in CD8+ T cells.

New directions for rabbit antithymocyte globulin (Thymoglobulin(®)) in solid organ transplants, stem cell transplants and autoimmunity

In the 30 years since the rabbit antithymocyte globulin (rATG) Thymoglobulin^® was first licensed, its use in solid organ transplantation and hematology has expanded progressively. Although the evidence base is incomplete, specific roles for rATG in organ transplant recipients using contemporary dosing strategies are now relatively well-identified. The addition of rATG induction to a standard triple or dual regimen reduces acute cellular rejection, and possibly humoral rejection. It is an appropriate first choice in patients with moderate or high immunological risk, and may be used in low-risk patients receiving a calcineurin inhibitor (CNI)-sparing regimen from time of transplant, or if early steroid withdrawal is planned. Kidney transplant patients at risk of delayed graft function may also benefit from the use of rATG to facilitate delayed CNI introduction. In hematopoietic stem cell transplantation, rATG has become an important component of conventional myeloablative conditioning regimens, following demonstration of reduced acute and chronic graft-versus-host disease. More recently, a role for rATG has also been established in reduced-intensity conditioning regimens. In autoimmunity, rATG contributes to the treatment of severe aplastic anemia, and has been incorporated in autograft projects for the management of conditions such as multiple sclerosis, Crohn’s disease, and systemic sclerosis. Finally, research is underway for the induction of tolerance exploiting the ability of rATG to induce immunosuppresive cells such as regulatory T-cells. Despite its long history, rATG remains a key component of the immunosuppressive armamentarium, and its complex immunological properties indicate that its use will expand to a wider range of disease conditions in the future.

Recollective homeostasis and the immune consequences of peritransplant depletional induction therapy

One's cellular immune repertoire is composed of lymphocytes in multiple stages of maturation - the dynamic product of their responses to antigenic challenges and the homeostatic contractions necessary to accommodate immune expansions within physiologic norms. Given that alloreactivity is predominantly a cross-reactive phenomenon that is stochastically distributed throughout the overall T-cell repertoire, one's allospecific repertoire is similarly made up of cells in a variety of differentiation states. As such, the continuous expansion and elimination of activated memory populations, producing a 'recollective homeostasis' of sorts, has the potential over time to alter the maturation state and effector composition of both ones protective and alloreactive T-cell repertoire. Importantly, a T cell's maturation state significantly influences its response to numerous immunomodulatory therapies used in organ transplantation, including depletional antibody induction. In this review, we discuss clinically utilized depletional induction strategies, how their use alters a transplant recipient's cellular immune repertoire, and how a recipient's repertoire influences the clinical effects of induction therapy.

Renal transplantation using belatacept without maintenance steroids or calcineurin inhibitors

Kidney transplantation remains limited by toxicities of calcineurin inhibitors (CNIs) and steroids. Belatacept is a less toxic CNI alternative, but existing regimens rely on steroids and have higher rejection rates. Experimentally, donor bone marrow and sirolimus promote belatacept's efficacy. To investigate a belatacept-based regimen without CNIs or steroids, we transplanted recipients of live donor kidneys using alemtuzumab induction, monthly belatacept and daily sirolimus. Patients were randomized 1:1 to receive unfractionated donor bone marrow. After 1 year, patients were allowed to wean from sirolimus. Patients were followed clinically and with surveillance biopsies. Twenty patients were transplanted, all successfully. Mean creatinine (estimated GFR) was 1.10 ± 0.07 mg/dL (89 ± 3.56 mL/min) and 1.13 ± 0.07 mg/dL (and 88 ± 3.48 mL/min) at 12 and 36 months, respectively. Excellent results were achieved irrespective of bone marrow infusion. Ten patients elected oral immunosuppressant weaning, seven of whom were maintained rejection-free on monotherapy belatacept. Those failing to wean were successfully maintained on belatacept-based regimens supplemented by oral immunosuppression. Seven patients declined immunosuppressant weaning and three patients were denied weaning for associated medical conditions; all remained rejection-free. Belatacept and sirolimus effectively prevent kidney allograft rejection without CNIs or steroids when used following alemtuzumab induction. Selected, immunologically low-risk patients can be maintained solely on once monthly intravenous belatacept.

Emerging trends in infections among renal transplant recipients

Outcomes following renal and simultaneous kidney-pancreas transplants have improved significantly due to better surgical techniques and improved modalities of antirejection therapy. However, infection remains a significant cause of morbidity and mortality. The use of new modalities of immunosuppression and routine use of antimicrobial prophylaxis has changed the pattern of infections post-transplantation. Cytomegalovirus remains a significant problem and BK virus has emerged as an important pathogen. New antimicrobial agents are now available to treat infection, however, antimicrobial resistance remains a concern.

Lymphodepletional strategies in transplantation

Because lymphocytes were shown to mediate transplant rejection, their depletion has been studied as a mechanism of preventing rejection and perhaps inducing immunologic tolerance. Agents that profoundly deplete lymphocytes have included monoclonal antibodies, cytotoxic drugs, and radiation. We have studied several such agents but focused on antibodies that deplete not only peripheral blood lymphocytes, but also lymph node lymphocytes. Depletion of lymph node T lymphocytes appears to permit peripheral tolerance at least for T cells in animal models. Nevertheless, B-cell responses may be resistant to such approaches, and T memory cells are likewise relatively resistant to depleting antibodies. We review the experimental and clinical approaches to depletion strategies and outline some of the pitfalls of depletion, such as limitations of currently available agents, duration of tolerance, infection, and malignancy. It is notable that most tolerogenic strategies that have been attempted experimentally and clinically include depleting agents even when they are not named as the underlying strategy. Thus, there is an implicitly acknowledged role for reducing the precursor frequency of donor antigen-specific lymphocytes when approaching the daunting goal of transplant tolerance.

Memory T cells and their exhaustive differentiation in allograft tolerance and rejection

PURPOSE OF REVIEW

Memory T cells have emerged as a major threat to transplant survival; they are well equipped and well positioned to respond to antigens in an accelerated fashion. They participate in transplant rejection and resist interventions that usually contain naïve T cells. Thus, the means to prevent memory T cells from attacking allotransplants are an important issue in transplantation.

RECENT FINDINGS

Recent studies in other models suggest that effector T cells, which include both freshly activated T cells and memory T cells, can acquire 'an exhausted phenotype' in that they progressively lose their effector activities. This response is highly regulated, antigen specific, and driven primarily by antigen persistence. This exhausted phenotype has not been carefully explored in transplant models, and its role in transplant survival remains largely unknown.

SUMMARY

Studies of T-cell exhaustion may reveal additional facets of the fundamental mechanisms of transplant survival. T-cell exhaustion may be an alternative way of preventing memory development. Future studies are needed to further improve our understanding of T-cell exhaustion in transplantation.

The role of Thymoglobulin induction in kidney transplantation: an update

The rabbit antithymocyte globulin Thymoglobulin first became available over 25 yr ago and is the most widely used lymphocyte-depleting preparation in solid organ transplantation. Thymoglobulin targets a wide range of T-cell surface antigens as well as natural killer-cell antigens, B-cell antigens, plasma cell antigens, adhesion molecules and chemokine receptors, resulting in profound, long-lasting T-cell depletion. Randomized studies have established the anti-rejection efficacy of Thymoglobulin in kidney transplantation. Experimental and clinical data suggest that Thymoglobulin administration may ameliorate ischemia reperfusion injury, thus reducing the incidence of delayed graft function (DGF). Studies have demonstrated the benefit of using Thymoglobulin to facilitate immunosuppression minimization, both for corticosteroid and calcineurin inhibitor (CNI) withdrawal or avoidance, with potential improvement in cardiovascular and renal outcomes. The optimal cumulative dose for Thymoglobulin induction is 6-7.5 mg/kg, with vigilant short- and long-term monitoring of hematological status. Induction with Thymoglobulin is now indicated in immunologically high-risk patients, in those at increased risk of DGF and to maintain efficacy in low-risk transplant recipients receiving steroid or CNI minimization or avoidance regimens. We suggest that in future trials Thymoglobulin be tested with costimulation signal blockers and other immunosuppressants with the objective of establishing operational tolerance.

Associations of ABCB1 3435C>T and IL-10-1082G>A polymorphisms with long-term sirolimus dose requirements in renal transplant patients

BACKGROUNDS

Sirolimus (SRL) absorption and metabolism are affected by p-glycoprotein-mediated transport and CYP3A enzyme activity, which are further under the influences of cytokine concentrations. This retrospective study determined the associations of adenosine triphosphate-binding cassette, subfamily B, member 1 (ABCB1) 1236C>T, 2677 G>T/A, and 3435C>T, cytochrome P450, family 3, subfamily A, polypeptide 4 (CYP3A4) -392A>G, cytochrome P450, family 3, subfamily A, polypeptide 5 (CYP3A5) 6986A>G and 14690G>A, interleukin (IL)-10 -1082G>A, and tumor necrosis factor (TNF) -308G>A polymorphisms with SRL dose-adjusted, weight-normalized trough concentrations (C/D) at 7 days, and at 1, 3, 6, and 12 months after initiation of SRL.

METHODS

Genotypes for 86 renal transplant patients who received SRL-based maintenance immunosuppressive therapy were determined using polymerase chain reaction followed by chip-based mass spectrometry. The changes of log-transformed C/D over the days posttransplantation were analyzed using a linear mixed-effects model, with adjustments for body mass index and weight-normalized doses of tacrolimus, prednisone, clotrimazole, and statins.

RESULTS

ABCB1 3435C>T and IL-10 -1082G>A were significantly associated with log C/D (P=0.0016 and 0.0394, respectively). Mean SRL C/D was 48% higher in patients with ABCB1 3435CT/TT genotype than those with 3435CC genotype, and was 24% higher in IL-10 -1082GG compared with -1082AG/AA.

CONCLUSIONS

ABCB1 3435C>T and IL-10 -1082G>A were significantly associated with long-term SRL dose requirements. Genetics can play a significant role in SRL dosing and may be useful in therapeutic monitoring of SRL in renal transplantation. Future replication studies are needed to confirm these associations.

Immunosuppression in the era of biological agents

Immunosuppression is the mayor mechanism to prevent allograft rejection and to induce tolerance. Since the first solid organ transplant, the development of safe and effective immunosuppressive regimens was a constant over the last decades. A lot of immunosuppressants have been discovered, and today the immunosuppressive agents are classified in two broad groups: Xenobiotic immunosuppressants and biological immunosuppressants. Xenobiotics, like corticoids and calcineurin and mTOR inhibitors, mainly interfere with the intracellular molecular mechanisms of the various types of cells involved in the immune response and generally these immunosuppressants are used early on in the transplantation process to prevent rejection as well as in long-term maintenance therapy. On the other hand, target molecules of biological immunosuppressants are on the surface of these immunological cells and normally in clinical immunosuppressive protocols have been used as auxiliary agents of xenobiotics to prevent rejection as well as in the treatment of acute rejection. However, these xenobiotics and biological agents have multiple side effects; that is why there has been a search for new drugs to minimise these side effects and to improve patients' quality of life. In this way, new biological agents have been proposed as maintenance immunosuppressive agents. The majority of these new immunosuppressive agents are polyclonal or monoclonal antibodies and recently the so-called fusion proteins may be the start of a new era of biological immunosuppression for maintenance regimens.

Regulation of immune responses by mTOR

mTOR is an evolutionarily conserved serine/threonine kinase that plays a central role in integrating environmental cues in the form of growth factors, amino acids, and energy. In the study of the immune system, mTOR is emerging as a critical regulator of immune function because of its role in sensing and integrating cues from the immune microenvironment. With the greater appreciation of cellular metabolism as an important regulator of immune cell function, mTOR is proving to be a vital link between immune function and metabolism. In this review, we discuss the ability of mTOR to direct the adaptive immune response. Specifically, we focus on the role of mTOR in promoting differentiation, activation, and function in T cells, B cells, and antigen-presenting cells.

Paradoxical aspects of rapamycin immunobiology in transplantation

Rapamycin has long been considered an immunosuppressive agent due to its antiproliferative effects on immune cells, and is currently used as a component of antirejection regimens in transplantation. Despite the large number of mechanistic and clinical studies investigating the impact of rapamycin on cell-mediated immunity, several paradoxes concerning rapamycin immunobiology remain. In particular, emerging evidence suggests that under certain circumstances rapamycin can exert immunostimulatory effects, boosting T cell responses in the face of pathogen infections and vaccines. Here, we review recent findings concerning the contradictory outcomes of rapamycin induced mTOR inhibition on CD4(+) and CD8(+) T cell responses in transplantation and protective immunity. These studies suggest that the conditions under which T cells are stimulated can profoundly modify the impact of rapamycin on antigen-specific T cell responses. Thus, further investigation into the cellular and molecular pathways underlying the dichotomous effects of rapamycin in transplantation is required to harness the full potential of this immunomodulatory agent to promote graft survival and maximize protective immunity.

The mammalian target of rapamycin: linking T cell differentiation, function, and metabolism

In the two-signal model of T cell activation, the outcome of antigen recognition is determined by the integration of multiple cues in the immune microenvironment. mTOR is an evolutionarily conserved PI3-kinase family member that plays a central role in integrating environmental cues in the form of amino acids, energy, and growth factors. Recently, an increasingly important role for mTOR in directing T cell activation and differentiation has become apparent. Here we review recent findings demonstrating the ability of mTOR to interpret signals in the immune microenvironment and program the generation of CD4(+) effector versus regulatory T cells, the generation of CD8(+) effector versus memory cells, T cell trafficking, and T cell activation versus anergy. The key theme to emerge from these studies is that the central role of mTOR provides a direct link between T cell metabolism and function.

ATG-Fresenius treatment and low-dose tacrolimus: results of a randomized controlled trial in liver transplantation

We report the results of a prospective randomized controlled trial in liver transplantation assessing the efficacy and safety of antithymocyte globulin (ATG-Fresenius) plus tacrolimus monotherapy at gradually decreasing doses. Patients were randomized to either: (a) standard-dose tacrolimus plus steroids;or (b) peritransplant ATG-Fresenius plus reduced-dose tacrolimus monotherapy followed by weaning of tacrolimus starting 3 months after transplantation. The primary end-point was the achievement of very low-dose tacrolimus (every-other-day or once daily dose with <5 ng/mL trough levels) at 12 months after transplantation. Acute rejection occurring during the first 3 months after transplantation was more frequent in the ATG group (52.4% vs. 25%). Moreover, late acute rejection episodes occurred in all recipients in whom weaning was attempted and no recipients reached the primary end-point. This motivated the premature termination of the trial. Tacrolimus trough levels were lower in the ATG-Fresenius group but no benefits in terms of improved renal function, lower metabolic complications or increased prevalence of tolerance-related biomarkers were observed. In conclusion, the use of ATG-Fresenius and tacrolimus at gradually decreasing doses was associated with a high rate of rejection, did not allow for the administration of very low doses of tacrolimus and failed to provide detectable clinical benefits. ClinicalTrials.gov identifier: NCT00436722.

Elevated myeloid: plasmacytoid dendritic cell ratio associates with late, but not early, liver rejection in children induced with rabbit anti-human thymocyte globulin

BACKGROUND

Dendritic cells (DC) play an important role in the induction and regulation of immune responses.

METHODS

Myeloid CD11c+ DC (MDC), which may have inflammatory functions, and plasmacytoid CD123+ DC (PDC), which may have tolerogenic potential, were measured by flow cytometric analysis, cross-sectionally, once, in 48 children, and longitudinally (pretransplant and at days 1-60, 61-200, and 201-400 posttransplant) in 30 children after liver transplantation (LTx). All children received cadaveric (n=53) or live donor (n=25) liver allografts with rabbit anti-human thymocyte globulin induction and steroid-free tacrolimus therapy. Rejectors in both groups were those children (n=35), who experienced biopsy-proven acute cellular rejection (ACR) within 60 days of DC monitoring.

RESULTS

Among rejectors in the longitudinal and cross-sectional cohorts, the MDC:PDC ratio was higher and was associated with decreased PDC frequencies. Logistic regression analysis, leave-one-out cross-validation, and receiver operating characteristic analysis applied to 30 cross-sectional subjects revealed that an MDC:PDC ratio more than or equal to 1.78 was associated with rejector status with sensitivity and specificity of 76.9% and 88.2%, respectively. Sensitivity and specificity were replicated in the 18 remaining cross-sectional subjects (88.8% and 78.8%, respectively), but not in longitudinally monitored subjects, during the early 60-day period after LTx (30.76% and 62.50%, respectively). A significant negative correlation was observed between tacrolimus whole blood concentrations and PDC frequencies (Spearman r=-0.370, P=0.005) in 48 cross-sectional subjects in whom DC subsets were monitored 1 to 3 years after LTx, but not during the early post-LTx period.

CONCLUSIONS

We conclude that an elevated MDC:PDC ratio associates with liver graft rejection, which occurs after first year in children induced with rabbit anti-human thymocyte globulin.

Induction of tolerance in solid organ transplantation: the rationale to develop clinical protocols in liver transplantation

Minimization or withdrawal of immunosuppressive treatments after organ transplantation represents a major objective for improving quality of life and long-term survival of grafted patients. Such a goal may be reached under some clinical conditions, particularly in liver transplantation, making these patients good candidates for tolerance trials. In this context in liver transplantation, the central questions are (1) how to promote the natural propensity of the liver graft to be accepted, (2) which type of immunosuppressive drug should be used for induction and maintenance, and (3) which biomarkers could be used to discriminate tolerant patients from those requiring long-term immunosuppression. Induction therapies using aggressive T-cell-depleting agents may favor graft acceptance. However, persistent and/or rapidly reemerging cell lines, such as memory-type cells or CD8(+) T cells, could represent a significant barrier for induction of tolerance. The type of maintenance drugs also remains questionable. Calcineurin inhibitors may be eventually deleterious in the context of tolerance protocols, through inhibitory effects on regulatory T cells, that are not observed with rapamycin. In conclusion, significant efforts must be made to achieve reliable strategies for immunosuppression minimization or withdrawal after organ transplantation into the clinics.

Relevance of cytotoxic alloreactivity under different immunosuppressive regimens in clinical islet cell transplantation

Islet or beta cell transplantation provides a promising cure for type 1 diabetes patients, but insulin-independency decreases frequently over time. Immunosuppressive regimens are implemented attempting to cope with both auto- and alloimmunity after transplantation. We analysed the influence of different immunotherapies on autoreactive and alloreactive T cell patterns and transplant outcome. Patients receiving three different immunosuppressive regimens were analysed. All patients received anti-thymocyte globulin induction therapy. Twenty-one patients received tacrolimus-mycophenolate mofetil maintenance immunosuppression, whereas the other patients received tacrolimus-sirolimus (SIR, n = 5) or SIR only (n = 5). Cellular autoreactivity and alloreactivity (CTL precursor frequency) were measured ex vivo. Clinical outcome in the first 6 months after transplantation was correlated with immunological parameters. C-peptide levels were significantly different between the three groups studied (P = 0.01). We confirm that C-peptide production was correlated negatively with pretransplant cellular autoreactivity and low graft size (P = 0.001, P = 0.007 respectively). Combining all three therapies, cellular autoimmunity after transplantation was not associated with delayed insulin-independence or C-peptide production. In combined tacrolimus-SIR and SIR-treated patients, CTL alloreactivity was associated with less insulin independence and C-peptide production (P = 0.03). The percentage of donors to whom high CTLp frequencies were measured was lower in insulin-independent recipients (P = 0.03). In this cohort of islet cell graft recipients, clinical outcome in the first 6 months after transplantation correlates with the applied immunosuppressive regimen. An association exists between insulin-independence and lower incidence of CTL alloreactivity towards donor human leucocyte antigen. This observational study demonstrates the usefulness of monitoring T cell reactivity against islet allografts to correlate immune function with graft survival.

New directions for induction immunosuppression strategy in solid organ transplantation

BACKGROUND

Solid organ transplant centers are increasingly using induction immunosuppression strategies. Induction immunosuppression involves the use of intense therapy at the time of transplantation with the goal of preventing acute rejection and ultimately inducing a tolerogenic state. The objective of this review is to examine specialized induction agents currently in clinical use and highlight novel therapeutics on the horizon for induction immunosuppression.

METHODS

A literature search using the PubMed and MEDLINE databases identified salient basic science and clinical research articles on induction immunosuppression for solid organ transplantation.

CONCLUSIONS

While current induction immunosuppression agents have reduced the incidence of acute rejection, the goal of transplant tolerance has not been realized. Furthermore, the long-term allograft survival rate is not clearly influenced by the practice of induction immunosuppression. New approaches to tolerance induction, such as costimulatory-based therapy, mixed chimerism, and adoptive cellular transfer, hold promise for more effective induction immunosuppression in solid organ transplantation.

A systematic approach to minimizing wound problems for de novo sirolimus-treated kidney transplant recipients

BACKGROUND

Wound healing problems and lymphoceles have been reported with greater frequency in kidney recipients given de novo sirolimus. This problem has led to increased patient morbidity and cost; and has been an impediment to the completion of randomized controlled trials in which wound problems have necessitated premature discontinuation of mammalian target of rapamycin inhibitors.

METHODS

We developed a systematic program to reduce these problems based on patient selection (body mass index [BMI] <32 kg/m2), the use of closed suction drains, modifications of surgical technique, and avoidance of a loading dose of sirolimus. Consecutive series of adult kidney-only recipients given antibody induction followed by de novo sirolimus, mycophenolate mofetil, and steroids were compared; group 1: 204 patients transplanted with few restrictions and group 2: 103 patients transplanted using the above program.

RESULTS

This approach resulted in a significant reduction (group 2 vs. group 1) in cumulative wound complications (7.8% vs. 19.6%, P=0.007), and nonoperative wound complications (2.9% vs. 14.2%, P=0.001). In addition, the incidence of lymphoceles detected (22.3% vs. 47.1%, P<0.0001), treated (4.8% vs. 24.5%, P<0.0001), or needing surgical intervention (1.9% vs. 14.2%, P=0.001) was significantly reduced. Multivariate analysis demonstrated that a BMI more than 30 to 32 kg/m2 was the most significant variable related to delayed wound healing (odds ratio [OR] 3.01, 0.02) or surgical repair (OR 8.05, P=0.0001), whereas BMI (OR 1.54, P=0.038) and acute rejections (OR 1.34, P=0.03) were most associated with lymphocele treatment.

CONCLUSIONS

A systematic program of wound care using de novo sirolimus can produce wound healing complications comparable with that reported with other agents.

Tolerance-inducing immunosuppressive strategies in clinical transplantation: an overview

The significant development of immunosuppressive drug therapies within the past 20 years has had a major impact on the outcome of clinical solid organ transplantation, mainly by decreasing the incidence of acute rejection episodes and improving short-term patient and graft survival. However, long-term results remain relatively disappointing because of chronic allograft dysfunction and patient morbidity or mortality, which is often related to the adverse effects of immunosuppressive treatment. Thus, the induction of specific immunological tolerance of the recipient towards the allograft remains an important objective in transplantation. In this article, we first briefly describe the mechanisms of allograft rejection and immune tolerance. We then review in detail current tolerogenic strategies that could promote central or peripheral tolerance, highlighting the promises as well as the remaining challenges in clinical transplantation. The induction of haematopoietic mixed chimerism could be an approach to induce robust central tolerance, and we describe recent encouraging reports of end-stage kidney disease patients, without concomitant malignancy, who have undergone combined bone marrow and kidney transplantation. We discuss current studies suggesting that, while promoting peripheral transplantation tolerance in preclinical models, induction protocols based on lymphocyte depletion (polyclonal antithymocyte globulins, alemtuzumab) or co-stimulatory blockade (belatacept) should, at the current stage, be considered more as drug-minimization rather than tolerance-inducing strategies. Thus, a better understanding of the mechanisms that promote peripheral tolerance has led to newer approaches and the investigation of individualized donor-specific cellular therapies based on manipulated recipient regulatory T cells.

Lymphocyte subset reconstitution in pediatric liver recipients induced with steroid-free rabbit anti-human thymocyte globulin

Multiple measurements of lymphocyte subsets in 91 children treated with steroid-free tacrolimus, and rabbit anti-human thymocyte globulin induction demonstrate early reconstitution of T-cytotoxic cells, and gradual reconstitution of all other subsets, which is complete after one yr. Rejection-prone children demonstrate significantly higher counts of lymphocytes and all subsets prior to liver transplantation, and may exemplify one basis for enhanced baseline immunocompetence.

Host CD4+CD25+ T cells can expand and comprise a major component of the Treg compartment after experimental HCT

Reconstitution of the recipient lymphoid compartment following hematopoietic cell transplantation (HCT) is typically delayed. The present studies investigated the residual host CD4(+)CD25(+)Foxp3(+) (Treg) compartment after several conditioning regimens, including T cell-depleted and T cell-replete HCT and observed (1) a small number of recipient Treg cells survived aggressive conditioning; (2) the surviving, that is, residual Tregs underwent marked expansion; and (3) recipient CD4(+)FoxP3(+) cells composed the majority of the Treg compartment for several months post-syngeneic HCT. Notably, residual Tregs also dominated the compartment post-HCT with T cell-depleted (TCD) major histocompatibility complex-matched allogeneic bone marrow but not following T cell-replete transplantations. The residual Treg cell compartment was functionally competent as assessed by in vitro lymphoid suppression and in vivo autoimmune disease transfer assay. These observations support the notion that functional host Tregs initially occupy a niche in lymphopenic transplantation recipients, undergo significant expansion, and contribute to the compartment for an extended period before donor-derived CD4(+)FoxP3(+) T cells eventually compose the majority of the compartment. In total, the findings suggest that the presence of host Tregs may be important to consider regarding elicitation of immune (eg, antitumor, vaccine) responses in recipients during the early post-transplant period involving autologous and certain allogeneic HCT regimens.

Minimization of calcineurin inhibitors to improve long-term outcomes in kidney transplantation

Long-term outcomes after kidney transplantation remain suboptimal, despite the great achievements observed in recent years with the use of modern immunosuppressive drugs. Currently, the calcineurin inhibitors (CNI) cyclosporine and tacrolimus remain the cornerstones of immunosuppressive regimens in many centers worldwide, regardless of their well described side-effects, including nephrotoxicity. In this article, we review recent CNI-minimization strategies in kidney transplantation, while emphasizing on the importance of long-term follow-up and patient monitoring. Finally, accumulating data indicate that low-dose CNI-based regimens would provide an interesting balance between efficacy and toxicity.

Immunosuppression without calcineurin inhibition: optimization of renal function in expanded criteria donor renal transplantation

INTRODUCTION

To assess the efficacy of calcineurin inhibitor (CNI)-free immunosuppression vs. calcineurin-based immunosuppression in patients receiving expanded criteria donor (ECD) kidneys.

PATIENT AND METHODS

Thirteen recipients of ECD kidneys were enrolled in this pilot study and treated with induction therapy and maintained on sirolimus, mycophenolate mofetil (MMF) and prednisone. A contemporaneous control group was randomly selected comprised of 13 recipients of ECD kidneys who had been maintained on CNI plus MMF and prednisone.

RESULTS

For the study group vs. the control group, two-yr graft survival was 92.3% vs. 84.6% (p = NS), two-yr patient survival was 100% vs. 92.3% (p = NS) and the acute rejection rates were 23% vs. 31% (p = NS), respectively. Renal function was significantly better in the study group compared with control up to the six-month mark, after which, it remained numerically but not statistically significant. Complications were more common in the study group, but serious adverse events requiring discontinuation were rare.

CONCLUSION

This pilot study demonstrates that CNI-free regimens can be safely implemented in patients receiving ECD kidneys with excellent two-yr patient and graft survival and good renal allograft function. Longer follow-up in larger randomized controlled trials are necessary to establish these findings.

A randomized trial of alemtuzumab vs. anti-thymocyte globulin induction in renal and pancreas transplantation

The role of alemtuzumab as an immunosuppressive agent is evolving. We conducted a prospective randomized trial comparing alemtuzumab and rabbit anti-thymocyte globulin (rATG) induction in adult kidney and pancreas transplantation using similar maintenance immunosuppression. Between February 1, 2005 and June 15, 2006 (median follow-up six months), 98 patients were randomized either to alemtuzumab (n = 48) or to rATG (n = 50) induction; 77 (79%) underwent kidney alone (KA) transplant, 17 (17%) pancreas-kidney transplant, and four (4%) pancreas after kidney transplant. Of 77 KA transplants, 66 (86%) were from deceased donors and 31 (40%) from expanded criteria donors (ECD). Re-transplantation, HLA-match, antibody titer, ECD, race, cytomegalovirus status, steroid use, delayed graft function, preservation time, and immunological risk were similar between the two induction groups. Patient, kidney, and pancreas graft survival rates were 100%, 96%, and 95%, respectively. Survival, initial length of stay, delayed graft function, and overall acute rejection rates were similar between alemtuzumab and rATG groups, but acute rejection occurred in nine (20%) rATG patients compared with zero (0%) alemtuzumab patients who received KA transplants (p = 0.007). Mean induction costs differed in the alemtuzumab ($1474) and rATG ($4996, p < 0.001) groups. In the short term after kidney and pancreas transplantation, alemtuzumab and rATG induction therapies are similarly safe and effective.

Exploiting novel molecular targets in gastrointestinal cancers

Novel molecular targets are being discovered as we learn more about the aberrant processes underlying various cancers. Efforts to translate this knowledge are starting to impact on the care of patients with gastrointestinal cancers. The epidermal growth factor receptor (EGFR) pathway and angiogenesis have been targeted successfully in colorectal cancer with cetuximab, panitunumab and bevacizumab. Similarly, EGFR-targeting with erlotinib yielded significant survival benefit in pancreatic cancer when combined with gemcitabine. The multi-targeting approach with sorafenib has made it the first agent to achieve significant survival benefit in hepatocellular carcinoma. Efforts to exploit the dysregulated Akt/mTOR pathway in GI cancer therapy are ongoing. These molecular targets can be disrupted by various approaches, including the use of monoclonal antibody to intercept extracellular ligands and disrupt receptor-ligand binding, and small molecule inhibitors that interrupt the activation of intracellular kinases.

Frontiers in nephrology: immune tolerance to allografts in humans

Vascularized allografts are rejected unless some indefinite modification to the recipient's immune system is made. This modification is typically achieved through the long-term administration of immunosuppressive drugs. Patients thus trade their end-stage organ failure for dependence on daily drug therapy and the accompanying chronic condition of immunodeficiency. However, it is clear from studies in experimental animals that rejection can be prevented through the use of several therapeutic approaches, including donor hematopoietic cell infusion, chimerism, T cell depletion, and/or co-stimulation blockade. Successfully treated animals avoid rejection beyond the period of therapy without a phenotype of chronic immunosuppression and are thus considered to be tolerant of their grafts. Although intriguing, this success in animals has yet to be reproducibly translated to the clinic, and human transplant recipients remain tethered to immunosuppressive drugs with rare exceptions. This article provides an overview of the existing, largely anecdotal, clinical experience with organ allograft tolerance. It reviews the various approaches that are being applied in pilot human trials and suggests avenues for future clinical investigation.

Calcineurin inhibitor-free immunosuppression in dual kidney transplantation from elderly donors

BACKGROUND

Kidneys from expanded-criteria donors may be particularly susceptible to calcineurin inhibitor (CI)-mediated vasoconstriction and nephrotoxicity. In the early post-transplant phase, using CI may prolong ischemic injury and, in the long term, chronic CI nephrotoxicity is an even greater concern. To avoid the acute and chronic consequences of CI in kidneys from marginal donors, CI-free protocols have been introduced for maintenance immunosuppressive therapy. A CI-free protocol of anti-thymocyte globulin (ATG) induction, sirolimus, mycophenolate mofetil (MMF) and steroids has been adopted at our center in recipients of dual kidney transplantation (DKT) from elderly donors (EDs).

METHODS

Dual kidney transplantations performed since April 2003 on CI-free immunosuppression (group 1 = 31) were compared with earlier DKTs in recipients treated with CI-based therapy (group 2 = 25), retrospectively analyzing patient and graft survival, surgical and medical complications, rejection episodes and renal function.

RESULTS

No deaths occurred after a mean follow-up of 10.1 +/- 7.6 (group 1) and 48.2 +/- 17.4 months (group 2). Graft loss occurred in one patient in group 1 (bilateral renal vein thrombosis) and in three patients in group 2 (one primary non-function [PNF], one chronic rejection, one Kaposi's sarcoma). The incidence of acute rejection was 19% in group 1 and 16% in group 2. Delayed graft function (DGF) was recorded in 16% and 48%, respectively. Renal function was better in group 1, with a mean S-Cr of 135 +/- 48 vs. 210 +/- 141 micromol/L at one month and 116 +/- 30 vs. 149 +/- 49 micromol/L at six months.

CONCLUSIONS

After DKT from EDs, a CI-free immunosuppressive regimen including ATG induction, sirolimus, MMF and steroids affords excellent results, with a lower DGF rate and a better renal function.

Tissue Transplantation in Plastic Surgery

The functional and aesthetic outcome following application of conventional reconstructive procedures or prosthetic materials is not satisfactory, especially in patients who have severe deformities and disabilities. Since the first successful hand transplantation in France in 1998, composite tissue allograft transplantation has gained a great deal of interest in the field of plastic surgery. It is obvious that composite tissue allograft transplantation will improve patients' life quality, but this might be at the expense of decreasing life expectancy. Currently, the main obstacle for composite tissue allograft transplantation is the use of life-long immunosuppression therapy because of their well-known side effects. In addition, the ethical, social, and psychologic issues are raised when discussing face transplantation. The long-term results of the recently performed partial face transplantations will be critical to judge the future applications of partial or total face transplantation.