Transplantation tolerance: from theory to clinic

Cell-Based Therapies Induce Tolerance of Vascularized Composite Allotransplants: A Systematic Review

INTRODUCTION

Vascularized composite allotransplantation (VCA) is the transplantation of multiple tissue types as a solution for devastating injuries. Despite the highly encouraging functional outcomes of VCA, the consequences of long-term immunosuppression remain the main obstacle in its application. In this review, we provide researchers and surgeons with a summary of the latest advances in the field of cell-based therapies for VCA tolerance.

METHODS

Four electronic databases were searched: PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature , and Web of Science. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analysis as the basis of our organization.

RESULTS

Hematopoietic stem cells prolonged VCA survival. A combination of immature dendritic cells and tacrolimus was superior to tacrolimus alone. T cell Ig domain and mucin domain modified mature dendritic cells increased VCA tolerance. Bone marrow-derived mesenchymal stem cells prolonged survival of VCAs. A combination of adipose-derived mesenchymal stem cells, cytotoxic T-lymphocyte antigen 4 immunoglobulin, and antilymphocyte serum significantly improved VCA tolerance. Ex-vivo allotransplant perfusion with recipient's bone marrow-derived mesenchymal stem cells increased VCA survival. Recipient's adipose-derived mesenchymal stem cells and systemic immunosuppression prolonged VCA survival more than any of those agents alone. Additionally, a combination of peripheral blood mononuclear cells shortly incubated in mitomycin and cyclosporine significantly improved VCA survival. Finally, a combination of donor recipient chimeric cells, anti-αβ-T cell receptor (TCR), and cyclosporine significantly prolonged VCA tolerance.

CONCLUSIONS

Evidence from animal studies shows that cell-based therapies can prolong survival of VCAs. However, there remain many obstacles for these therapies, and they require rigorous clinical research given the rarity of the subjects and the complexity of the therapies. The major limitations of cell-based therapies include the need for conditioning with immunosuppressive drugs and radiation, causing significant toxicity. Safety concerns also persist as most research is on animal models. While completely replacing traditional immunosuppression with cell-based methods is unlikely soon, these therapies could reduce the need for high doses of immunosuppressants and improve VCA tolerance.

Metabolically Glycoengineered Neural Stem Cells Boost Neural Repair After Cardiac Arrest

Cardiac arrest (CA)-induced cerebral ischemia remains challenging with high mortality and disability. Neural stem cell (NSC) engrafting is an emerging therapeutic strategy with considerable promise that, unfortunately, is severely compromised by limited cell functionality after in vivo transplantation. This groundbreaking report demonstrates that metabolic glycoengineering (MGE) using the "Ac5ManNTProp (TProp)" monosaccharide analog stimulates the Wnt/β-catenin pathway, improves cell adhesion, and enhances neuronal differentiation in human NSCs in vitro thereby substantially increasing the therapeutic potential of these cells. For the first time, MGE significantly enhances NSC efficacy for treating ischemic brain injury after asphyxia CA in rats. In particular, neurological deficit scores and neurobehavioral tests experience greater improvements when the therapeutic cells are pretreated with TProp than with "stand-alone" NSC therapy. Notably, the TProp-NSC group exhibits significantly stronger neuroprotective functions including enhanced differentiation, synaptic plasticity, and reduced microglia recruitment; furthermore, Wnt pathway agonists and inhibitors demonstrate a pivotal role for Wnt signaling in the process. These findings help establish MGE as a promising avenue for addressing current limitations associated with NSC transplantation via beneficially influencing neural regeneration and synaptic plasticity, thereby offering enhanced therapeutic options to boost brain recovery following global ischemia.

Dexamethasone priming enhances stemness and immunomodulatory property of tissue-specific human mesenchymal stem cells

BACKGROUND

Human Mesenchymal Stem Cells (hMSCs) represent a promising cell source for cell-based therapy in autoimmune diseases and other degenerative disorders due to their immunosuppressive, anti-inflammatory and regenerative potentials. Belonging to a glucocorticoid family, Dexamethasone (Dex) is a powerful anti-inflammatory compound that is widely used as therapy in autoimmune disease conditions or allogeneic transplantation. However, minimal immunomodulatory effect of hMSCs may limit their therapeutic uses. Moreover, the effect of glucocorticoids on the immunomodulatory molecules or other regenerative properties of tissue-specific hMSCs remains unknown.

METHOD

Herein, we evaluated the in vitro effect of Dex at various dose concentrations and time intervals, 1000 ng/ml, 2000 ng/ml, 3000 ng/ml and 24 h, 48 h respectively, on the basic characteristics and immunomodulatory properties of Bone marrow derived MSC (BM-MSCs), Adipose tissue derived MSCs (AD-MSCs), Dental Pulp derived MSC (DP-MSCs) and Umbilical cord derived MSCs (UC-MSCs).

RESULTS

The present study indicated that the concentration of Dex did not ramify the cellular morphology nor showed cytotoxicity as well as conserved the basic characteristics of tissue specific hMSCs including cell proliferation and surface marker profiling. However, quite interestingly it was observed that the stemness markers (Oct-4, Sox-2, Nanog and Klf-4) showed a significant upregulation in DP-MSCs and AD-MSCs followed by UC-MSCs and BM-MSCs. Additionally, immunomodulatory molecules, Prostaglandin E-2 (PGE-2), Indoleamine- 2,3-dioxygenase (IDO) and Human Leukocyte Antigen-G (HLA-G) were seen to be upregulated in a dose-dependent manner. Moreover, there was a differential response of tissue specific hMSCs after pre-conditioning with Dex during mixed lymphocyte reaction, wherein UC-MSCs and DP-MSCs showed enhanced immunosuppression as compared to AD-MSCs and BM-MSCs, thereby proving to be a better candidate for therapeutic applications in immune-related diseases.

CONCLUSION

Dex preconditioning improved the hMSCs immunomodulatory property and may have reduced the challenge associated with minimal potency and strengthen their therapeutic efficacy. Preconditioning of tissue specific hMSCs with dexamethasone biomanufacturers the enhanced potential hMSCs with better stemness and immunomodulatory properties for future therapeutics.

Progress in Liver Transplant Tolerance and Tolerance-Inducing Cellular Therapies

Liver transplantation is currently the most effective method for treating end-stage liver disease. However, recipients still need long-term immunosuppressive drug treatment to control allogeneic immune rejection, which may cause various complications and affect the long-term survival of the recipient. Many liver transplant researchers constantly pursue the induction of immune tolerance in liver transplant recipients, immunosuppression withdrawal, and the maintenance of good and stable graft function. Although allogeneic liver transplantation is more tolerated than transplantation of other solid organs, and it shows a certain incidence of spontaneous tolerance, there is still great risk for general recipients. With the gradual progress in our understanding of immune regulatory mechanisms, a variety of immune regulatory cells have been discovered, and good results have been obtained in rodent and non-human primate transplant models. As immune cell therapies can induce long-term stable tolerance, they provide a good prospect for the induction of tolerance in clinical liver transplantation. At present, many transplant centers have carried out tolerance-inducing clinical trials in liver transplant recipients, and some have achieved gratifying results. This article will review the current status of liver transplant tolerance and the research progress of different cellular immunotherapies to induce this tolerance, which can provide more support for future clinical applications.

Chimerism, Transplant Tolerance, and Beyond

The present review discusses current developments in tolerance induction for solid organ transplantation with a particular emphasis on chimerism-based approaches. It explains the basic mechanisms of chimerism-based tolerance and provides an update on ongoing clinical tolerance trials. The concept of "delayed tolerance" is presented, and ongoing preclinical studies in the nonhuman primate setting-including current limitations and hurdles regarding this approach-are illustrated. In addition, a brief overview and update on cell-based tolerogenic clinical trials is provided. In a critical approach, advantages, limitations, and potential implications for the future of these different regimens are discussed.

Innate Immune Determinants of Graft-Versus-Host Disease and Bidirectional Immune Tolerance in Allogeneic Transplantation

The success of tissue transplantation from a healthy donor to a diseased individual (allo-transplantation) is regulated by the immune systems of both donor and recipient. Developing a state of specific non-reactivity between donor and recipient, while maintaining the salutary effects of immune function in the recipient, is called “immune (transplantation) tolerance”. In the classic early post-transplant period, minimizing bidirectional donor ←→ recipient reactivity requires the administration of immunosuppressive drugs, which have deleterious side effects (severe immunodeficiency, opportunistic infections, and neoplasia, in addition to drug-specific reactions and organ toxicities). Inducing immune tolerance directly through donor and recipient immune cells, particularly via subsets of immune regulatory cells, has helped to significantly reduce side effects associated with multiple immunosuppressive drugs after allo-transplantation. The innate and adaptive arms of the immune system are both implicated in inducing immune tolerance. In the present article, we will review innate immune subset manipulations and their potential applications in hematopoietic stem cell transplantation (HSCT) to cure malignant and non-malignant hematological disorders by inducing long-lasting donor ←→ recipient (bidirectional) immune tolerance and reduced graft-versus-host disease (GVHD). These innate immunotherapeutic strategies to promote long-term immune allo-transplant tolerance include myeloid-derived suppressor cells (MDSCs), regulatory macrophages, tolerogenic dendritic cells (tDCs), Natural Killer (NK) cells, invariant Natural Killer T (iNKT) cells, gamma delta T (γδ-T) cells and mesenchymal stromal cells (MSCs).

Inducción de tolerancia inmunológica: alotrasplantes compuestos vascularizados y trasplantes de órgano sólido

Introducción. La inducción de tolerancia inmunológica solucionaría los problemas asociados con la inmunosupresión de por vida, necesaria para evitar el rechazo de aloinjertos.Objetivos. Revisar aspectos inmunológicos, modelos clínicos utilizados y resultados obtenidos en la tolerancia y comparar los resultados obtenidos con trasplante de órgano sólido y alotrasplante compuesto vascularizado.Materiales y métodos. Se realizó una búsqueda en la base de datos PubMed que arrojó 299 resultados; se revisaron las bibliografías de los artículos y se consultaron las referencias pertinentes. Al final se seleccionaron 83 artículos.Resultados. Existen mecanismos centrales y periféricos para mantener la tolerancia a antígenos propios; en la práctica clínica, la tolerancia central ha sido más utilizada, esto se ha hecho mediante estrategias que utilizan trasplante conjunto de medula ósea. Varios ensayos clínicos, la mayoría en pacientes con trasplante renal, han mostrado resultados prometedores pero inconsistentes.Conclusiones. En trasplantes renales fue posible suspender de forma exitosa la inmunosupresión, mientras que en trasplantes de mano se logró disminuirla considerablemente. El quimerismo inmunológico parece ser indispensable para el desarrollo de tolerancia a aloinjertos, por lo que es necesario desarrollar protocolos para inducir quimerismo mixto persistente.

Cooperation of CD4+ T cells and CD8+ T cells and release of IFN-γ are critical for antileukemia responses of recipient mice treated by microtransplantation

Previous studies have demonstrated that infusion of allogeneic matched and haploidentical peripheral blood stem cells with minimal conditioning (microtransplantation) achieved durable responses in patients with refractory leukemia/lymphoma in the absence of engraftment. The mechanisms underlying this response have not been thoroughly elucidated, while host-versus-graft reactions are likely to have an important role. The present study established a mismatched microtransplantation mouse model of leukemia to study the roles of CD4⁺ T cells and CD8⁺ T cells in changes of interferon (IFN)-γ and interleukin (IL)-4 release to explore the mechanisms of the effects of microtransplantation. It was demonstrated that IFN-γ is critical to the antileukemia response in a mouse model of microtransplantation. The therapeutic efficacy was associated with the number of CD4⁺ T cells (Pearson's r=0.722). In addition, CD8⁺ T cells increased the release of IFN-γ with assistance from CD4⁺ T cells. IL-2 augmented IFN-γ release, partly by increasing CD4⁺ T cells (42.8 vs. 35.6%; P<0.05). The present study suggested that the release of IFN-γ via cooperation of CD4⁺ T cells and CD8⁺ T cells represents a crucial mechanism in the antileukemia responses of recipient leukemic mice treated by microtransplantation. During this process, the cooperation of CD4⁺ T cells and CD8⁺ T cells was demonstrated to have a major role in the antileukemia effect. IL-2 may be developed into an agent used for improving the efficacy of microtransplantation by increasing CD4⁺ T cells.

Technique for orthotopic liver transplantation in cynomolgus monkeys (Macaca fascicularis)

Purpose

Recent studies investigating new strategies to modulate the immune system have utilized animal models of liver transplantation (LT). However, the anhepatic phase (AHP) remains a crucial problem in LT. The aim of the present study is to introduce a technique for successful orthotopic LT in cynomolgus monkeys using an early-reperfusion strategy.

Methods

Orthotopicallo-LT was performed with seven donor/recipient pairs of cynomolgus monkeys.

Results

In 2 recipients, liver allografts were perfused after suprahepatic inferior vena cava (SHIVC), portal vein (PV), and infrahepatic inferior vena cava (IHIVC) anastomosis. To reduce the time of AHP in five recipients, liver allografts ware perfused after SHIVC and PV anastomosis while the IHIVC was not anastomosed. In the latter strategy, the AHP was reduced from 46 minutes to 31 minutes and a 24-hour survival rate of 80% was achieved.

Conclusion

Our results indicate that an early-reperfusion strategy can be successfully used to establish a LT model in cynomolgus monkeys with a consistently high rate of animal survival.

Combining Adoptive Treg Transfer with Bone Marrow Transplantation for Transplantation Tolerance

PURPOSE OF REVIEW

The mixed chimerism approach is an exceptionally potent strategy for the induction of donor-specific tolerance in organ transplantation and so far the only one that was demonstrated to work in the clinical setting. Regulatory T cells (Tregs) have been shown to improve chimerism induction in experimental animal models. This review summarizes the development of innovative BMT protocols using therapeutic Treg transfer for tolerance induction.

RECENT FINDINGS

Treg cell therapy promotes BM engraftment in reduced conditioning protocols in both, mice and non-human primates. In mice, transfer of polyclonal recipient Tregs was sufficient to substitute cytotoxic recipient conditioning. Treg therapy prevented chronic rejection of skin and heart allografts related to tissue-specific antigen disparities, in part by promoting intragraft Treg accumulation.

SUMMARY

Adoptive Treg transfer is remarkably effective in facilitating BM engraftment in reduced-intensity protocols in mice and non-human primates. Furthermore, it promotes regulatory mechanisms that prevent chronic rejection.

Young donor white blood cell immunotherapy induces extensive tumor necrosis in advanced-stage solid tumors

Background

In the past decade, a variety of immunotherapy approaches focused predominantly on the adaptive immune system have shown unprecedented responses in patients with advanced-stage malignancies. However, studies in spontaneous regression/complete resistance (SR/CR) mice and humans have shown a novel innate cancer-killing activity mediated by granulocytes, which is completely transferable for prevention or therapy against established malignancies.

Methods

Three patients with advanced, relapsed or refractory solid tumors for which no standard therapy was available or was refused were enrolled into this ongoing combined phase I/II open label clinical trial testing the safety, dose tolerance, and possible antineoplastic efficacy of sequential infusions of HLA-mismatched non-irradiated allogeneic white cells (68–91% granulocytes) collected by leukapheresis from young, healthy donors (age 18–35) following mobilization with granulocyte colony stimulating factor (G-CSF) and dexamethasone.

Results

Besides fevers and flushing, no infusional toxicities were observed. All patients remained clinically stable following infusions with mild cytokine release syndrome and no evidence of transfusion-associated graft-versus-host disease, acute tumor lysis syndrome,or transfusion-associated acute lung injury. Pathological examination of all cases post-mortem revealed extensive tumor necrosis up to 80% in patients 1–2, 40–50% in patient 3, and leukocyte infiltration in all cases, which could not be attributed to disease progression.

Conclusions

Allogeneic white cell immunotherapy (AWIT) from young, healthy donors is well tolerated with minimal side effects and shows antitumor activity against advanced-stage solid tumors. AWIT represents a novel, safe, and cost-effective immunotherapy that can be administered in an outpatient cancer clinic.

Prolonged Survival of Subcutaneous Allogeneic Islet Graft by Donor Chimerism without Immunosuppressive Treatment

The aim of this study was to investigate whether tolerance-induced protection of islets in the renal subcapsular space can also prevent subcutaneous allogeneic islets from being rejected. We used bone marrow stem cells from C57BL/6 (H2^b) mice to construct donor chimerism in conditioned diabetic BALB/c (H2^d) mice and investigated the effect of donor chimerism on engraftment and survival of subcutaneously transplanted allogeneic islets in streptozotocin-induced diabetic mice. We also studied the anti-inflammatory effect of mesenchymal stem cell on islet engraftment. Full but not low-grade or no donor chimerism was associated with successful engraftment of allogeneic islets and restoration of normoglycemia in the treated diabetic mice. The temporary hyperglycemia was 11 ± 1 versus 19 ± 5 days (p < 0.05) for the mice with full donor chimerism with transplanted islets in the renal subcapsular space versus the subcutaneous space, respectively. Cotransplantation of mesenchymal stem cell did not enhance alloislet engraftment. Full multilineage donor chimerism was associated with a higher transient expansion of CD11b⁺ and Gr-1⁺ myeloid progenitor cells and effector memory CD4 and CD8 T cells. In conclusion, full donor chimerism protected both renal subcapsular and subcutaneous allogeneic islets in this rodent transplantation model.

Frequency of fetal-maternal microchimerism: an analysis of the HLA-DRB1 gene in cord blood and maternal sample pairs

PURPOSE

We aimed to investigate the frequency of fetal-maternal microchimerism among cord blood (CB) from a Korean population.

MATERIALS AND METHODS

We previously developed a nested polymerase chain reaction-single-strand conformation polymorphism method for microchimerism detection that is highly sensitive (0.01-0.001%) and specific. We used this method to investigate the frequency of fetal-maternal HLA-DRB1 microchimerism among 153 maternal and 152 CB samples.

RESULTS

Among the tested pairs, 41.1% exhibited at least one direction of microchimerism, 32.0% of the mothers possessed fetal microchimerism, and 23.4% of the newborns possessed maternal microchimerism. The overall microchimerism frequency was 28.2%.

CONCLUSIONS

We hypothesize that the different microchimerism frequencies among population and methods are due to differences in detection specificities and subject characteristics. This study provides basic data on fetal-maternal microchimerism that may be useful for future studies on autoimmune disorder and virtual phenotyping in transplantation.

Outcomes of pediatric identical living-donor liver and hematopoietic stem cell transplantation

Chronic IS is associated with significant morbidity in transplant recipients. Moreover, IS does not prevent chronic graft failure frequently. Allograft immune tolerance in LT can be induced by complete donor chimerism through allogenic HSCT combined with identical LDLT. This approach may exempt patients from chronic lifelong IS. However, it is unclear whether its benefits justify its risks. Here, we present three cases from our institution and analyze seven additional reports of children treated with HSCT/LDLT, all receiving HSCT due to hemato-oncological indications. In eight of 10 cases, donor macrochimerism resulted in allograft tolerance. Nine patients survived. One patient died due to fulminant ADV infection. Further complications were GvHD (n = 3) and bone marrow failure (n = 2). In conclusion, donor-specific allograft tolerance can be achieved by identical-donor HSCT/LDLT. However, at present, this approach should generally be limited to selected indications due to a potentially unfavorable risk-benefit ratio. Novel toxicity-reduced conditioning protocols for HSCT/LDLT in the absence of malignant or non-hepatic disease may prove to be a sufficiently safe approach for inducing graft tolerance in children receiving a LDLT in the future. This concept may reduce the burden of lifelong IS.

Immunosuppression for in vivo research: state-of-the-art protocols and experimental approaches

Almost every experimental treatment strategy using non-autologous cell, tissue or organ transplantation is tested in small and large animal models before clinical translation. Because these strategies require immunosuppression in most cases, immunosuppressive protocols are a key element in transplantation experiments. However, standard immunosuppressive protocols are often applied without detailed knowledge regarding their efficacy within the particular experimental setting and in the chosen model species. Optimization of such protocols is pertinent to the translation of experimental results to human patients and thus warrants further investigation. This review summarizes current knowledge regarding immunosuppressive drug classes as well as their dosages and application regimens with consideration of species-specific drug metabolization and side effects. It also summarizes contemporary knowledge of novel immunomodulatory strategies, such as the use of mesenchymal stem cells or antibodies. Thus, this review is intended to serve as a state-of-the-art compendium for researchers to refine applied experimental immunosuppression and immunomodulation strategies to enhance the predictive value of preclinical transplantation studies.

3K3A-activated protein C stimulates postischemic neuronal repair by human neural stem cells in mice

Activated protein C (APC) is a blood protease with anticoagulant activity and cell-signaling activities mediated by the activation of protease-activated receptor 1 (F2R, also known as PAR1) and F2RL1 (also known as PAR3) via noncanonical cleavage. Recombinant variants of APC, such as the 3K3A-APC (Lys191-193Ala) mutant in which three Lys residues (KKK191-193) were replaced with alanine, and/or its other mutants with reduced (>90%) anticoagulant activity, engineered to reduce APC-associated bleeding risk while retaining normal cell-signaling activity, have shown benefits in preclinical models of ischemic stroke, brain trauma, multiple sclerosis, amyotrophic lateral sclerosis, sepsis, ischemic and reperfusion injury of heart, kidney and liver, pulmonary, kidney and gastrointestinal inflammation, diabetes and lethal body radiation. On the basis of proof-of-concept studies and an excellent safety profile in humans, 3K3A-APC has advanced to clinical trials as a neuroprotectant in ischemic stroke. Recently, 3K3A-APC has been shown to stimulate neuronal production by human neural stem and progenitor cells (NSCs) in vitro via a PAR1-PAR3-sphingosine-1-phosphate-receptor 1-Akt pathway, which suggests the potential for APC-based treatment as a strategy for structural repair in the human central nervous (CNS) system. Here we report that late postischemic treatment of mice with 3K3A-APC stimulates neuronal production by transplanted human NSCs, promotes circuit restoration and improves functional recovery. Thus, 3K3A-APC-potentiated neuronal recruitment from engrafted NSCs might offer a new approach to the treatment of stroke and related neurological disorders.

BAFF upregulates CD28/B7 and CD40/CD154 expression and promotes mouse T and B cell interaction in vitro via BAFF receptor

AIM

B cell-activating factor belonging to the TNF family (BAFF) is a member of TNF family and required for peripheral B cell survival and homeostasis. BAFF has been shown to promote the proliferation of T and B cells. In this study we examined whether and how BAFF mediated the interaction between mouse T and B cells in vitro.

METHODS

BAFF-stimulated B or T cells were co-cultured with T or B cells. The interactions between T and B cells were analyzed by measuring the expression of co-stimulatory molecules (CD28/CD80 or CD40/CD154), the proliferation and secretion of T and B cells and other factors. Two siRNAs against the transmembrane activator and calcium modulator and cyclophilin ligand interactor (TACI) and BAFF receptor (BAFF-R) were used to identify the receptors responsible for the actions of BAFF.

RESULTS

BAFF-stimulated B cells significantly promoted the proliferation and activity of co-cultured T cells, and increased the percentages of CD4(+)CD28(+) and CD4(+)CD154(+) T cells. Similarly, BAFF-stimulated T cells significantly promoted the proliferation and activity of co-cultured B cells, and increased CD19(+)CD80(+) and CD19(+)CD40(+)B cell subpopulations. BAFF-R siRNA-silenced B cells showed significantly lower expression of CD40 and CD80 than the control B cells. When the BAFF-R siRNA-silenced B cells were stimulated with BAFF, then co-cultured with T cells, the expression of CD28 and CD154 on T cells was not increased. TACI siRNA-silenced B cells exhibited higher expression of CD40 and CD80 than the control B cells. When the TACI siRNA-silenced B cells were stimulated with BAFF, then co-cultured with T cells, the expression of CD28 and CD154 on T cells was significantly increased.

CONCLUSION

BAFF upregulates CD28/B7 and CD40/CD154 expression, and promotes the interactions between T and B cells in a BAFF-R-dependent manner.

Added effects of dexamethasone and mesenchymal stem cells on early Natural Killer cell activation

Graft rejection and graft-versus-host disease are leading causes of transplant related mortality despite advancements in immunosuppressive therapy. Mesenchymal stem cells (MSCs) offer a promising addition to immunosuppressive drugs (ISD), while NK-cells are increasingly used as effector cells in graft-versus-leukemia. Combined therapy of ISD, NK-cells and/or MSCs is used in clinical practice. Here, we examined the effects of MSCs and selected ISD (tacrolimus, cyclosporin A, mycophenolic acid, dexamethasone) treatment on early NK-cell activation. We assessed STAT4 and STAT5 phosphorylation triggered by IL-12 and IL-2, respectively. Furthermore, we determined IFNγ, perforin production and the expression pattern of selected NK-cell receptors. Of all drugs tested, only dexamethasone inhibited NK-cell STAT4 and STAT5 phosphorylation. All ISD, with the exception of MPA, significantly inhibited IFNγ, and only dexamethasone inhibited upregulation of early activation markers CD69 and CD25 (IL-2 condition only). MSCs inhibited IL-2 induced NK cell STAT5 phosphorylation, IFNγ production and CD69 upregulation, and IL-12 induced IFNγ and perforin production. While MSCs mediated inhibition of CD69 expression was cell contact dependent, inhibition of IFNγ and perforin production, as well as STAT5 phosphorylation was cell-contact independent. Importantly, dexamethasone augmented MSCs mediated inhibition of both IL-12 and IL-2 induced CD69 expression and IFNγ production, as well as IL-2 induced STAT5 phosphorylation. Taken together, these novel insights may help the design of future NK-cell and MSCs based immunotherapy.

Banking on iPSC--is it doable and is it worthwhile

The discovery of induced pluripotent stem cells (iPSCs) and concurrent development of protocols for their cell-type specific differentiation have revolutionized studies of diseases and raised the possibility that personalized medicine may be achievable. Realizing the full potential of iPSC will require addressing the challenges inherent in obtaining appropriate cells for millions of individuals while meeting the regulatory requirements of delivering therapy and keeping costs affordable. Critical to making PSC based cell therapy widely accessible is determining which mode of cell collection, storage and distribution, will work. In this manuscript we suggest that moderate sized bank where a diverse set of lines carrying different combinations of commonly present HLA alleles are banked and differentiated cells are made available to matched recipients as need dictates may be a solution. We discuss the issues related to developing such a bank and how it could be constructed and propose a bank of selected HLA phenotypes from carefully screened healthy individuals as a solution to delivering personalized medicine.

Human mesenchymal stromal cells attenuate graft-versus-host disease and maintain graft-versus-leukemia activity following experimental allogeneic bone marrow transplantation

We sought to define the effects and underlying mechanisms of human, marrow-derived mesenchymal stromal cells (hMSCs) on graft-versus-host disease (GvHD) and graft-versus-leukemia (GvL) activity. Irradiated B6D2F1 mice given C57BL/6 BM and splenic T cells and treated with hMSCs had reduced systemic GvHD, donor T-cell expansion, and serum TNFα and IFNγ levels. Bioluminescence imaging demonstrated that hMSCs redistributed from lungs to abdominal organs within 72 hours, and target tissues harvested from hMSC-treated allogeneic BMT (alloBMT) mice had less GvHD than untreated controls. Cryoimaging more precisely revealed that hMSCs preferentially distributed to splenic marginal zones and regulated T-cell expansion in the white pulp. Importantly, hMSCs had no effect on in vitro cytotoxic T-cell activity and preserved potent GvL effects in vivo. Mixed leukocyte cultures containing hMSCs exhibited decreased T-cell proliferation, reduced TNFα, IFNγ, and IL-10 but increased PGE2 levels. Indomethacin and E-prostanoid 2 (EP2) receptor antagonisms both reversed while EP2 agonism restored hMSC-mediated in vitro T-cell suppression, confirming the role for PGE2 . Furthermore, cyclo-oxygenase inhibition following alloBMT abrogated the protective effects of hMSCs. Together, our data show that hMSCs preserve GvL activity and attenuate GvHD and reveal that hMSC biodistribute to secondary lymphoid organs wherein they attenuate alloreactive T-cell proliferation likely through PGE2 induction.

Regulatory T Cells in Kidney Transplantation: New Directions?

The contribution of regulatory T cells in the maintenance of kidney graft survival is of major interest. Although many experimental models suggest a role in the induction of graft tolerance, reproducing these findings in clinic is less clear. While modulation of the regulatory T cell response is a promising therapeutic concept in transplantation, a better understanding of function, phenotype and biology is needed to be able to optimally exploit these cells in order to induce graft tolerance. With this in mind, we review here the current understanding of the phenotypic-functional delineation of Tregs and how Tregs can contribute to graft survival. We highlight their potential role in long-term graft survival and kidney operational tolerance. We also discuss the mechanisms needed for the molecular development of regulatory T cells: A combination of FOXP3 molecular partners, epigenetic, metabolic, and posttranslational modifications are necessary to generate well-functioning regulatory T cells and maintain their core identify. We discuss how an improved understanding of these mechanisms will permit the identification of new potent therapeutic strategies to improve kidney graft survival.

Cytomegalovirus infection in patients who underwent allogeneic hematopoietic stem cell transplantation in Portugal: a five-year retrospective review

Cytomegalovirus (CMV) infection is 1 of the leading causes of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (aHSCT), mainly within the first 100 days after transplantation. We aimed to characterize CMV infection in a cohort of 305 patients with different malignancies undergoing aHSCT at the Portuguese Institute of Oncology of Porto between January 2008 and December 2012. In total, 184 patients (60.3%) developed CMV infection, mainly viral reactivations rather than primary infections (96.2% versus 3.8%, respectively). The majority of patients (166 of 184) developed CMV infection ≤100 days after transplantation, with median time to infection of 29 days (range, 0 to 1285) and median duration of infection of 10 days (range, 2 to 372). Multivariate analysis revealed that CMV infection was increased in donor (D)-/recipient (R)+ and D+/R+ (odds ratio [OR], 10.5; 95% confidence interval [CI], 4.35 to 25.4; P < .001) and in patients with mismatched or unrelated donors (OR, 2.54; 95% CI, 1.34 to 4.80; P = .004). Cox regression model showed that the risk of death was significantly increased in patients >38 years old (OR, 1.89; 95% CI, 1.14 to 3.12; P = .0137), who underwent transplantation with peripheral blood (OR, 3.02; 95% CI, 1.33 to 6.86; P = .008), with mismatched or unrelated donor (OR, 2.16; 95% CI, 1.48 to 3.13; P < .001), and who developed CMV infection (OR, 1.76; 95% CI, 1.07 to 2.90; P = .025). Moreover, patients who developed CMV infection had a significantly reduced median post-transplantation survival (16 versus 36 months; P = .002).