Why is organ transplantation clinically important?

In situ repurposing of dendritic cells with CRISPR/Cas9-based nanomedicine to induce transplant tolerance

Organ transplantation is the only effective method to treat end-stage organ failure. However, it is continuously plagued by immune rejection, which is mostly caused by T cell-mediated reactions. Dendritic cells (DCs) are professional antigen-presenting cells, and blocking the costimulatory signaling molecule CD40 in DCs inhibits T cell activation and induces transplant tolerance. In this study, to relieve graft rejection, Cas9 mRNA (mCas9) and a guide RNA targeting the costimulatory molecule CD40 (gCD40) were prepared and encapsulated into poly(ethylene glycol)-block-poly(lactide-co-glycolide) (PEG-b-PLGA)-based cationic lipid-assisted nanoparticles (CLAN), denoted CLANmCas9/gCD40. CLAN effectively delivered mCas9/gCD40 into DCs and disrupted CD40 in DCs at the genomic level both in vitro and in vivo. After intravenous injection into an acute mouse skin transplant model, CLANmCas9/gCD40-mediated CD40 disruption significantly inhibited T cell activation, which reduced graft damage and prolonged graft survival. This work provides a promising strategy for reprogramming DCs with nanoparticles carrying the CRISPR/Cas9 system to abate transplant rejection.

The Novel N,N-bis-2-Hydroxyethyl-2-Aminoethanesulfonic Acid-Gluconate-Polyethylene Glycol-Hypothermic Machine Perfusion Solution Improves Static Cold Storage and Reduces Ischemia/Reperfusion Injury in Rat Liver Transplant

Organ transplantation is the treatment of choice against terminal and irreversible organ failure. Optimal preservation of the graft is crucial to counteract cold ischemia effects. As we developed an N,N-bis-2-hydroxyethyl-2-aminoethanesulfonic acid-gluconate-polyethylene glycol (BGP)-based solution (hypothermic machine perfusion [HMP]), we aimed to analyze the use of this solution on static cold storage (SCS) of rat livers for transplantation as compared with the histidine tryptophan ketoglutarate (HTK) preservation solution. Livers procured from adult male Sprague Dawley rats were preserved with BGP-HMP or HTK solutions. Liver total water content and metabolites were measured during the SCS at 0°C for 24 hours. The function and viability of the preserved rat livers were first assessed ex vivo after rewarming (90 minutes at 37°C) and in vivo using the experimental model of reduced-size heterotopic liver transplantation. After SCS, the water and glycogen content in both groups remained unchanged as well as the tissue glutathione concentration. In the ex vivo studies, livers preserved with the BGP-HMP solution were hemodynamically more efficient and the O₂ consumption rate was higher than in livers from the HTK group. Bile production and glycogen content after 90 minutes of normothermic reperfusion was diminished in both groups compared with the control group. Cellular integrity of the BGP-HMP group was better, and the histological damage was reversible. In the in vivo model, HTK-preserved livers showed a greater degree of histological injury and higher apoptosis compared with the BGP-HMP group. In conclusion, our results suggest a better role of the BGP-HMP solution compared with HTK in preventing ischemia/reperfusion injury in the rat liver model.

Knowledge, attitude, and perception on organ donation among undergraduate medical and nursing students at a tertiary care teaching hospital in the southern part of India: A cross-sectional study

BACKGROUND

Organ donation is considered to be a noble act. Medical and nursing students will be the major healthcare providers in this field in the future. Hence, their knowledge, attitude, and perception toward organ donation are essential to improve this field in the future.

OBJECTIVE

The objective of this study is to assess the knowledge, attitude, and perception on organ donation among undergraduate medical and nursing students. This study brings forth the basic understanding level of the medical and nursing students on the concept of organ donation.

METHODS

A cross-sectional descriptive study was conducted among the first 4 academic years of medical and nursing students in a tertiary care teaching hospital using convenient sampling. A total of 620 students participated in this study. They were assessed using a pretested semi-structured self-administered questionnaire. The data were analyzed using Statistical Package of the Social Sciences version 19.

RESULTS

The median score on knowledge, attitude, and perception among the medical students was 16 (14-17), 25 (23-28), and 41 (38-45), respectively, and among the nurses, the scores were 14 (12-16), 25 (22-27), and 39 (33-42), respectively. Almost half (46.9%) of the study participants knew the definition for brain death. Twenty-nine percent of the study participants knew about the existence of law toward organ donation; more than half of those participants (52.7%) mentioned few rules and regulation involved in the laws pertaining to organ donation.

CONCLUSION

Media is the major source for information. Only less than half of the study participants were knowledgeable on the definition of brain death and existence of organ donation law. Although they are in favor of organ donation, doubts still exist among few of the participants which could be understood through further research in this field.

Incidence of and risk factors for cryptococcosis in kidney transplant recipients in Taiwan-A nationwide population-based study

OBJECTIVES

The aim of this study was to determine the long-term incidence of cryptococcosis in kidney transplant recipients (KTRs) and to analyze its risk factors.

METHODS

This retrospective population-based cohort study analyzed data obtained from Taiwan's National Health Insurance Research Database for KTRs during 2000-2012 and matched cohorts. Both populations were followed until death, development of cryptococcosis, or December 2013.

RESULTS

A total of 4,933 KTRs and 49,930 matched patients were included. The cryptococcosis incidence rates for the KTR cohort and matched cohort were 10.59 and 0.4 per 10,000 person-years, respectively. The hazard ratio for cryptococcosis among KTRs was 26.65 (p<0.001); and 43.77 (p<0.001) for cryptococcosis affecting the central nervous system (CNS). The Kaplan-Meier method confirmed an elevated cumulative incidence of cryptococcosis among KTRs (1.00% vs. 0.04%). Predictors for cryptococcosis were advanced age (OR 1.39, 95% CI 1.02-1.89, P=0.038) and cancer (OR 2.63, 95% CI 1.22-5.67, P=0.013), but not the use of any particular class of immunosuppressants.

CONCLUSIONS

KTRs are at dramatically higher risk of developing cryptococcosis, especially with CNS involvement, relative to a non-KTR matched cohort. Older KTRs and those with cancer are at even higher risk of developing cryptococcosis.

Effectiveness of the Gerundium Youth Educating Program in Hungary

The acceptance of brain death and the legitimation of organ transplantation is very much dependent on the general knowledge of the society. In Hungary, the legislation of brain death is based on presumed consent. There is no structural education about the topic so far.

AIM

The role of the Gerundium program is to educate high school students about the importance of transplantation and the meaning of brain death. The goal of this study was to evaluate the effectiveness of the Gerundium contemporary educational program in a pilot study.

METHOD

The education was held by medical students who successfully completed a preparatory elective course consisting of relevant information in the topic. Medical students used simple language during the 45-minute presentations. Two tests with simple but representative questions created by experts were completed by high school students: one directly before contemporary education and another 5 to 6 weeks after the lecture.

RESULTS

A total of 147 tests were completed: 78 before and 69 after the presentation in the city of Debrecen and 294 before the lecture in the city of Győr. In Debrecen, the overall correct answers increased by 6.05% (P < .05; before vs after). The results show that the knowledge transfer is highly effective in this manner and the students know significantly more weeks after the lectures.

CONCLUSION

There is much to do to broadly inform society about transplantation and brain death, but we will continue to increase the number of students and measure the dynamic change of the students' knowledge.

False Immunosuppressant Measurement by LC-MS/MS Method Due to Radiopaque Agents

BACKGROUND

Although liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is preferred as a reliable method, some molecules in the blood matrix may lead to false positive or false negative results. False positive or negative results show the direction of the deviation rate from the target value.

AIM

The aim of this study was to investigate the effect of seven different radiopaque agents on four immunosuppressant drugs.

METHODS

Every agent coded with RM1 to RM7 was added to control materials containing tacrolimus, everolimus, sirolimus, and cyclosporine A drugs. Measurements were performed using an LC-MS/MS instrument. Bias values were calculated to detect the deviation rates.

RESULTS

All RMs led to false negative results in the tacrolimus and cyclosporine A levels at a rate of -19.77% (95% CI, -27.16 to 12.52) to -44.45% (95% CI, -49.20 to -39.69). The smallest deviations were seen in the everolimus levels with the administration of RM6 (gadodiamide) and in the sirolimus levels with RM1 (gadobutrol) at the rates of 4.04% (95% CI, -11.36 to -3.17) and 2.11% (95% CI, -7.18 to 7.11), respectively. The most affected drug by RM4 (gadopentetate dimeglumine salt) was sirolimus at the rate of 114.01% (95% CI, 97.31 - 130.76). RM5 (gadodiamide) interfered cyclosporine A at the most. The highest deviations were observed with the administration of RM3 (iohexol) in the everolimus and sirolimus levels at the rates of 153.72% (95% CI, 142.44 to 164.78) and 171.41% (95% CI, 157.91 to 184.97), respectively.

CONCLUSION

Radiopaque agents interfered the measurement of immunosuppressant drugs. Especially, everolimus and sirolimus levels were affected due to using iohexol. The choice of gadodiamide or ioversol is important to reduce the risk of interference for everolimus measurement. The blood samples should be obtained for measurement of drug levels before contrast-enhanced imaging.

In vitro osteogenic differentiation potential of the human induced pluripotent stem cells augments when grown on Graphene oxide-modified nanofibers

Due to the several limitations that surgeons are faced during bone tissue implantation there are daily increases in introducing new cell-co-polymer composites for use in bone tissue engineering approaches. In this study tried to develop a suitable nanostructured bio-composite for enhancing osteogenic differentiation of the human induced pluripotent stem cells (iPSCs). Polyvinylidene fluoride-Graphene oxide (PVDF-GO) nanofibers was fabricated by electrospinning and then characterized using scanning electron microscope, tensile and viability assays. After that osteogenic differentiation of the iPSCs was investigated in three groups, including PVDF, PVDF-GO and tissue culture plate as a control group. Alkaline phosphatase activity and calcium content of the iPSCs cultured on PVDF-GO were significantly higher than those cultured on other groups. In addition, Runx2, osteocalcin and osteonectin genes were up regulated in iPSCs cultured on PVDF-GO significantly higher than those cells cultured on PVDF and control. Finally, osteocalcin and osteopontin proteins expression evaluated and the results confirmed higher osteoinductivity of the PVDF-GO nanofibers in comparison with the PVDF nanofibers. According to the results, it was demonstrated that PVDF-GO nanofibers have a great osteoinductive potential and taking together iPSCs-PVDF-GO nanofibrous construct can be an appropriate bio-implant to use for bone tissue engineering applications.

Activation and Proliferation of PD-1+ Kidney Double-Negative T Cells Is Dependent on Nonclassical MHC Proteins and IL-2

BACKGROUND

CD4^- CD8^- double-negative (DN) αβ T cells with innate-like properties represent a significant component of T cells in human and mouse kidneys. They spontaneously proliferate in the steady state and protect against ischemic AKI. However, the mechanisms regulating DN T cell homeostasis and responses to external danger signals from "sterile" inflammation remain poorly understood.

METHODS

We used knockout mice, functional assays, and an established ischemic AKI model to investigate the role of various MHC class I and II molecules in regulating kidney DN T cells. We also studied human nephrectomy samples.

RESULTS

Deficiency of β2m-dependent MHC class I (but not MHC class II) molecules led to significant reduction in frequency or absolute numbers of kidney DN T cells due to impaired activation, proliferation, increased apoptosis, and loss of an NK1.1⁺ subset of DN T cells. The remaining DN T cells in β2m knockout mice mainly comprised a programmed cell death protein-1 receptor (PD-1⁺) subset that depends on IL-2 provided by conventional T cells for optimal homeostasis. However, this PD-1⁺ subset remained highly responsive to changes in milieu, demonstrated by responses to infused lymphocytes. It was also the major responder to ischemic AKI; the NK1.1⁺ subset and CD8⁺ T cells had minimal responses. We found both DN T cell subsets in normal and cancerous human kidneys, indicating possible clinical relevance.

CONCLUSIONS

DN T cells, a unique population of kidney T cells, depend on nonclassical β2m molecules for homeostasis and use MHC-independent mechanisms to respond to external stimuli. These results have important implications for understanding the role these cells play during AKI and other immune cell-mediated kidney diseases.

ImmunoSPdb: an archive of immunosuppressive peptides

Immunosuppression proved as a captivating therapy in several autoimmune disorders, asthma as well as in organ transplantation. Immunosuppressive peptides are specific for reducing efficacy of immune system with wide range of therapeutic implementations. `ImmunoSPdb’ is a comprehensive, manually curated database of around 500 experimentally verified immunosuppressive peptides compiled from 79 research article and 32 patents. The current version comprises of 553 entries providing extensive information including peptide name, sequence, chirality, chemical modification, origin, nature of peptide, its target as well as mechanism of action, amino acid frequency and composition, etc. Data analysis revealed that most of the immunosuppressive peptides are linear (91%), are shorter in length i.e. up to 20 amino acids (62%) and have L form of amino acids (81%). About 30% peptide are either chemically modified or have end terminal modification. Most of the peptides either are derived from proteins (41%) or naturally (27%) exist. Blockage of potassium ion channel (24%) is one a major target for immunosuppressive peptides. In addition, we have annotated tertiary structure by using PEPstrMOD and I-TASSER. Many user-friendly, web-based tools have been integrated to facilitate searching, browsing and analyzing the data. We have developed a user-friendly responsive website to assist a wide range of users.

Hamilton-DONATE: a city-wide pilot observational study of the ICU management of deceased organ donors

PURPOSE

Improving the medical care of deceased organ donors to increase transplant rates and improve allograft function requires an understanding of the current epidemiology and clinical practices of deceased donation within intensive care units (ICUs). Herein, we report the results of our investigation into the feasibility of a multicentre prospective cohort study addressing the afformentioned issues.

METHODS

We conducted a 12-month prospective observational cohort study in six ICUs and one coronary care unit in Hamilton, Canada. We included consecutive children and adults following consent for deceased organ donation (including neurologic determination of death [NDD] or donation after circulatory death [DCD]). Intensive care unit research staff recorded donor management data from hospital records, extending from one day prior to the consent for organ donation up to the time of organ retrieval. The provincial Organ Donation Organization (ODO) supplemented these data and, additionally, provided data on corresponding organ recipients. We identified, evaluated, and measured three potential obstacles to the feasibility of a national cohort study: obtaining authorization to implement the study with a waiver of research consent, accessibility of transplant recipient data, and the time required to complete very detailed case report forms (CRFs), with valuable lessons learned for implementation in future projects.

RESULTS

The local Research Ethics Board and the ODO Privacy Office both authorized the recording of donor and recipient study data with a waiver of research consent. Sixty-seven consecutive consented donors were included (31 NDD and 36 DCD donors); 50 of them provided 144 organs for transplantation to 141 recipients. We identified the age and sex of the recipients as well as the location and date of transplant for all organ recipients in Ontario; however, we obtained no recipient data for six organs transported outside of Ontario. Intensive care unit research staff estimated that future CRF completion will require five to seven hours per patient.

CONCLUSION

The Hamilton-DONATE pilot study supports the feasibility of a larger cohort study to describe the epidemiology and clinical practices related to deceased donor care in Canada.

TRIAL REGISTRATION

wwwclinicaltrials.gov (NCT02902783). Registered 16 September 2016.

Organ donation by patients with and without trauma in a Canadian province: a retrospective cohort analysis

BACKGROUND

People who experience trauma represent a large pool of potential organ donors. Our objective was to describe organ donation by patients with and without trauma in Nova Scotia.

METHODS

We performed a retrospective cohort study of all patients with trauma in the Nova Scotia Trauma Registry who were injured between Apr. 1, 2009, and Mar. 31, 2016, and died in hospital, as well as all potential organ donors captured in the Nova Scotia Legacy of Life Donor Registry over the same period. We compared characteristics of the 2 groups with respect to organ donation and identified reasons for nondonation.

RESULTS

Overall, 940 patients were included in the analysis, of whom 689 (73.3%) had experienced trauma. Patients with trauma accounted for 37.2% (48/129) of donors. A total of 274 (39.8%) of the patients with trauma were identified as potential organ donors, and 48 (7.0%) donated organs. Only 108 (39.4%) of the 274 were referred to the Legacy of Life Program. The conversion rate (proportion of potential donors who went on to donate an organ) was 84.2% (48/57) among patients with trauma and 83.5% (81/97) among those without trauma. Donation after circulatory death occurred in 8 patients (17%) with trauma and 13 (16%) of those without trauma. Family refusal (28/60 [47%]) and medical unsuitability (16/60 [27%]) were the most common reasons for nondonation among patients with trauma.

INTERPRETATION

In Nova Scotia, 40% of patients with trauma who died in hospital were potential organ donors, yet only 39% of these patients were referred for donation. More work is required to improve organ donation within the trauma population.

Expanding transplant outcomes research opportunities through the use of a common data model

The volume of solid organ transplant in the United States is increasing, providing improved quality of life and survival for patients with organ failure. The growth of transplant requires a systematized management of transplant outcomes assessment, especially with the movement toward value-based care. However, there are several challenges to analyzing outcomes in the current registry-based, transplant reporting system: (1) longitudinal data points are difficult to capture in outcomes models; (2) data elements are restricted to those that already exist in the registry data; and (3) there is a delay in the release of outcomes report. In this article, we propose an informatics approach to solve these problems by using a "common data model" to integrate disparate data sources, data elements, and temporal data points. Adopting such a framework can enable multicenter outcomes analyses among transplant centers, nationally and internationally.

Organ Transplantation in Iran; Current State and Challenges with a View on Ethical Consideration

Organ transplantation is a new issue in medical science. It is an important achievement and a sign of the progression and ability of medical centers around the world. Governments, populations, the medical community and people involved in culture, art, and media all have a decisive role in the culture of organ donation, which is the only way to guarantee that the healthy organs of a brain-dead person can continue to work and save the lives of people in need of organ transplantation. The brain death phenomenon and its possible application in organ transplantation, while offering new hope for the salvation of a number of patients, has led to many ethical, cultural, and legal issues. Ethical issues in organ transplantation are very complicated due to many social factors such as religion, culture, and traditions of the affected communities. The ethical and legal points of removing organs from the body of a living or cadaveric source, the definition of brain death, the moral and legal conditions of the donor and the recipient, and the financial relationship between them and many others, are all critical issues in organ transplantation. While there may be no available explicit solution to these issues, they should be rigorously considered by the experts. Efforts to systematically eliminate barriers and solve problems in organ transplantation, can not only reduce the costs of maintaining brain-dead patients and encourage patients that need organ transplantation but can also prevent immoral and illegal activities. In this paper, we have reviewed the most important and current challenges in organ transplantation with a view to the ethical considerations, and we have suggested some strategies to extend it in Iran.

Transplantation Tolerance through Hematopoietic Chimerism: Progress and Challenges for Clinical Translation

The perception that transplantation of hematopoietic stem cells can confer tolerance to any tissue or organ from the same donor is widely accepted but it has not yet become a treatment option in clinical routine. The reasons for this are multifaceted but can generally be classified into safety and efficacy concerns that also became evident from the results of the first clinical pilot trials. In comparison to standard immunosuppressive therapies, the infection risk associated with the cytotoxic pre-conditioning necessary to allow allogeneic bone marrow engraftment and the risk of developing graft-vs.-host disease (GVHD) constitute the most prohibitive hurdles. However, several approaches have recently been developed at the experimental level to reduce or even overcome the necessity for cytoreductive conditioning, such as costimulation blockade, pro-apoptotic drugs, or Treg therapy. But even in the absence of any hazardous pretreatment, the recipients are exposed to the risk of developing GVHD as long as non-tolerant donor T cells are present. Total lymphoid irradiation and enriching the stem cell graft with facilitating cells emerged as potential strategies to reduce this peril. On the other hand, the long-lasting survival of kidney allografts, seen with transient chimerism in some clinical series, questions the need for durable chimerism for robust tolerance. From a safety point of view, loss of chimerism would indeed be favorable as it eliminates the risk of GVHD, but also complicates the assessment of tolerance. Therefore, other biomarkers are warranted to monitor tolerance and to identify those patients who can safely be weaned off immunosuppression. In addition to these safety concerns, the limited efficacy of the current pilot trials with approximately 40-60% patients becoming tolerant remains an important issue that needs to be resolved. Overall, the road ahead to clinical routine may still be rocky but the first successful long-term patients and progress in pre-clinical research provide encouraging evidence that deliberately inducing tolerance through hematopoietic chimerism might eventually make it from dream to reality.

Tacrolimus Utilization and Expenditure in Serbia

Background

Increasing immunosuppressant consumption and expenditure is a quite a challenge in transplantation medicine. The aim of the study was to characterize the utilization and expenditure of tacrolimus, backbone, and standard of care in immunosuppression regimen in Serbian solid organ transplant recipients.

Methods

This study was performed as retrospective cross-sectional study during a 3-year period (from 2013 to 2015) in Serbia. The Anatomical Therapeutic Chemical Classification/Defined Daily Doses (ATC/DDD) international system was used for consumption evaluation.

Results

Two hundred and sixty-nine patients were transplanted in Serbia from 2013 to 2015 (185 recipients from deceased donors and 84 recipients from living donors). Total number of deceased donors in this period was 81. The consumption of tacrolimus increased (from 0.051 DDD/1,000 inhabitants/day to 0.069 DDD/1,000 inhabitants/day in 2013 and 2015, respectively). The total cost of tacrolimus was also increased; from 1,206,816€ to 1,483,472€ in 2013 and 2015, respectively. On the other hand, the number of all new solid organ transplants (from deceased and living donors) per million population per year was decreased from 17.39 to 10.02, from 2013 to 2015, respectively.

Conclusion

In spite downward trend in the number of solid organ transplants, tacrolimus consumption and expenditure in the examined 3-year period in Serbia increased. Since tacrolimus is a high-cost and life-preserving drug, its increasing utilization and expenditure will most likely continue consuming an enhancing share of Serbian pharmaceutical expenditure, as well as its health care, as a whole.

Murine models of transplantation tolerance through mixed chimerism: advances and roadblocks

Organ transplantation is the treatment of choice for patients with end-stage organ failure, but chronic immunosuppression is taking its toll in terms of morbidity and poor efficacy in preventing late graft loss. Therefore, a drug-free state would be desirable where the recipient permanently accepts a donor organ while remaining otherwise fully immunologically competent. Mouse studies unveiled mixed chimerism as an effective approach to induce such donor-specific tolerance deliberately and laid the foundation for a series of clinical pilot trials. Nevertheless, its widespread clinical implementation is currently prevented by cytotoxic conditioning and limited efficacy. Therefore, the use of mouse studies remains an indispensable tool for the development of novel concepts with potential for translation and for the delineation of underlying tolerance mechanisms. Recent innovations developed in mice include the use of pro-apoptotic drugs or regulatory T cell (Treg ) transfer for promoting bone marrow engraftment in the absence of myelosuppression and new insight gained in the role of innate immunity and the interplay between deletion and regulation in maintaining tolerance in chimeras. Here, we review these and other recent advances in murine studies inducing transplantation tolerance through mixed chimerism and discuss both the advances and roadblocks of this approach.

The mechanisms of rejection in solid organ transplantation

Organ transplantation represents the preferred treatment option for many patients in terminal organ failure. The half-life of transplanted organs, however, is still far from being satisfactory with the vast majority of the organs failing within the first two decades following transplantation. At this stage, it has become apparent that rejection (prevalently mediated by humoral events) remains the primary cause of graft loss after the first year. In this light, studies are underway to better comprehend the immune events underlying graft rejection and novel immunosuppressive strategies are being explored. In this context, therapeutic apheresis techniques, that include therapeutic plasma exchange (TPE), immunoadsorption (IA) and extracorporeal photochemotherapy (ECP), represent an important adjunct in the current immunosuppressive armamentarium. This article briefly reviews our current understanding of the immune process underlying rejection of a solid organ transplant and describes the principal areas of application of therapeutic apheresis techniques in transplantation.

Splenocyte Infusion and Whole-Body Irradiation for Induction of Peripheral Tolerance in Porcine Lung Transplantation: Modifications of the Preconditioning Regime for Improved Clinical Feasibility

BACKGROUND

Preoperative low-dose whole-body irradiation (IRR) with 1.5 and 7 Gy thymic IRR of the recipient, combined with a perioperative donor splenocyte infusion lead to reliable donor specific peripheral tolerance in our allogeneic porcine lung transplantation model. To reduce the toxicity of this preconditioning regime, modifications of the IRR protocol and their impact on allograft survival were assessed.

METHODS

Left-sided single lung transplantation from major histocompatibility complex and sex mismatched donors was performed in 14 adult female minipigs. Recipient animals were exposed to 3 different protocols of nonmyeloablative IRR within 12 hours before transplantation. All animals were administered a donor splenocyte infusion on the day of lung transplantation. Intravenous pharmacologic immunosuppression was withdrawn after 28 postoperative days. Allograft survival was monitored by chest radiographs and bronchoscopy.

RESULTS

IRR prolonged transplant survival in a dose- and field-dependent manner. Shielding of the bone marrow from IRR (total lymphoid IRR at 1.5 and 7 Gy thymic IRR) significantly reduced protocol toxicity defined as thrombocytopenia and consecutive increased bleeding propensity, but had a less effective impact on graft survival. Whole-body IRR at 0.5 and 7 Gy thymic IRR proved to be ineffective for reliable tolerance induction. Eventually, high levels of circulating CD4⁺CD25^high regulatory T cells were present in long-term survivors.

CONCLUSIONS

These data show that the infusion of donor-specific alloantigen in combination with IRR is efficient once a threshold dose is exceeded.

Tempering allorecognition to induce transplant tolerance with chemically modified apoptotic donor cells

The development of organ transplantation as a therapy for end-stage organ failure is among the most significant achievements of 20th century medicine, but chronic rejection remains a barrier to achieving long-term success. Current therapeutic regimens consist of immunosuppressive drugs that are efficient at delaying rejection but are associated with significant risks such as opportunistic infections, toxicity, and malignancy. Thus, the induction of specific immune tolerance to transplant antigens is the coveted aim of researchers. The use of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (ECDI)-treated, autoantigen-coupled syngeneic leukocytes has been developed as a specific immunotherapy in preclinical models of autoimmunity and is currently in a phase II clinical trial for the treatment of multiple sclerosis. In this review, we discuss the use of allogeneic ECDI-treated apoptotic donor leukocytes (allo-ECDI-SP) as a strategy for inducing antigen-specific tolerance in allogeneic transplantation. Allo-ECDI-SP therapy induces long-term systemic immune tolerance to transplant antigens by subverting alloimmune recognition and exploiting apoptotic cell uptake pathways to recapitulate innate mechanisms of peripheral tolerance. Lastly, we discuss potential indications and challenges for transitioning allo-ECDI-SP therapy into clinical practice.

The use of novel diagnostics to individualize immunosuppression following transplantation

Despite major improvements in short-term survival of organ allografts, long-term graft survival has not changed significantly. It is also known that toxic side effects of current immunosuppressive drugs (IS) especially calcineurin inhibitors (CNI) contribute to the unsatisfactory graft and patient survival following transplantation. Thus, clinicians strive to reduce or wean IS in potentially eligible patients. Research in the last 10 years has focussed on identification of biomarkers suitable for patient stratification in minimization or weaning trials. Most of the described biomarkers have been run retrospectively on samples collected within single-centre trials. Thus, often their performance has not been validated in other potentially multicentre clinical trials. Ultimately, the utility of biomarkers to identify potential weaning candidates should be investigated in large randomized prospective trials. In particular, for testing in such trials, we need more information about the accuracy, reproducibility, stability and limitations of the described biomarkers. Also, data repositories summarizing crucial information on biomarker performance in age- and gender-matched healthy individuals of different ethnicity are missing. This together with improved bioinformatics tools might help in developing better scores for patient stratification. Here, we will summarize the current results, knowledge and limitations on biomarkers for drug minimization or weaning trials.

Transplantation tolerance: from theory to clinic

Tolerance induction and alloreactivity can be applied to the clinic for the transplantation of solid organs and in the treatment of human cancers respectively. Hematopoietic chimerism, the stable coexistence of host and donor blood cells, guarantees that a solid organ from the same donor will be tolerated without a requirement for maintenance immunosuppression, and it also serves as a platform for the adoptive immunotherapy of hematologic malignancies using donor lymphocyte infusions. This review focuses on clinically relevant methods for inducing hematopoietic chimerism and transplantation tolerance, with a special emphasis on reduced intensity transplantation conditioning and high dose, post-transplantation cyclophosphamide to prevent graft rejection and graft-versus-host disease (GVHD). Reduced intensity transplantation regimens permit a transient cooperation between donor and host immune systems to eradicate malignancy without producing GVHD. Their favorable toxicity profile also enables the application of allogeneic stem cell transplantation to treat non-malignant disorders of hematopoiesis and to induce tolerance for solid organ transplantation.

Tolerance--is it worth it?

We are entering an exciting time in the study of immunologic tolerance. Several cellular and molecular strategies have been developed that show promise in nonhuman transplant models and these approaches are just now appearing in clinical trials. Tolerance strategies that prevent immune rejection and obviate the need for immunosuppressive medications (with inherent risk of cancer, infection, and organ toxicity) would improve both graft and patient survival. Each tolerance protocol brings its own set of associated risks. As the results of these trials become available, we must continue to evaluate their successes and failures. The balance of these outcomes will help us answer the question: "Tolerance-Is it worth it?"