Rapamycin promotes the enrichment of CD4(+)CD25(hi)FoxP3(+) T regulatory cells from naïve CD4(+) T cells of baboon that suppress antiporcine xenogenic response in vitro

Sustained store-operated calcium entry utilizing activated chromatin state leads to instability in iTregs

Thymus-originated tTregs and in vitro induced iTregs are subsets of regulatory T cells. While they share the capacity of immune suppression, their stabilities are different, with iTregs losing their phenotype upon stimulation or under inflammatory milieu. Epigenetic differences, particularly methylation state of Foxp3 CNS2 region, provide an explanation for this shift. Whether additional regulations, including cellular signaling, could directly lead phenotypical instability requires further analysis. Here, we show that upon TCR (T cell receptor) triggering, SOCE (store-operated calcium entry) and NFAT (nuclear factor of activated T cells) nuclear translocation are blunted in tTregs, yet fully operational in iTregs, similar to Tconvs. On the other hand, tTregs show minimal changes in their chromatin accessibility upon activation, in contrast to iTregs that demonstrate an activated chromatin state with highly accessible T cell activation and inflammation related genes. Assisted by several cofactors, NFAT driven by strong SOCE signaling in iTregs preferentially binds to primed-opened T helper (TH) genes, resulting in their activation normally observed only in Tconv activation, ultimately leads to instability. Conversely, suppression of SOCE in iTregs can partially rescue their phenotype. Thus, our study adds two new layers, cellular signaling and chromatin accessibility, of understanding in Treg stability, and may provide a path for better clinical applications of Treg cell therapy.

Cotreatment With Clofazimine and Rapamycin Eliminates Drug-Resistant Tuberculosis by Inducing Polyfunctional Central Memory T-Cell Responses

Mycobacterium tuberculosis, the causative agent of tuberculosis, is acquiring drug resistance at a faster rate than the discovery of new antibiotics. Therefore, alternate therapies that can limit the drug resistance and disease recurrence are urgently needed. Emerging evidence indicates that combined treatment with antibiotics and an immunomodulator provides superior treatment efficacy. Clofazimine (CFZ) enhances the generation of T central memory (TCM) cells by blocking the Kv1.3+ potassium channels. Rapamycin (RAPA) facilitates M. tuberculosis clearance by inducing autophagy. In this study, we observed that cotreatment with CFZ and RAPA potently eliminates both multiple and extensively drug-resistant (MDR and XDR) clinical isolates of M. tuberculosis in a mouse model by inducing robust T-cell memory and polyfunctional TCM responses. Furthermore, cotreatment reduces the expression of latency-associated genes of M. tuberculosis in human macrophages. Therefore, CFZ and RAPA cotherapy holds promise for treating patients infected with MDR and XDR strains of M. tuberculosis.

The case for the therapeutic use of mechanistic/mammalian target of rapamycin (mTOR) inhibitors in xenotransplantation

The mechanistic/mammalian target of rapamycin (mTOR) is one of the systems that are necessary to maintain cell homeostasis, such as survival, proliferation, and differentiation. mTOR inhibitors (mTOR-Is) are utilized as immunosuppressants and anti-cancer drugs. In organ allotransplantation, current regimens infrequently include an mTOR-I, which are positioned more commonly as alternative immunosuppressants. In clinical allotransplantation, long-term efficacy has been established, but there is a significant incidence of adverse events, for example, inhibition of wound healing, buccal ulceration, anemia, hyperglycemia, dyslipidemia, and thrombocytopenia, some of which are dose-dependent. mTOR-Is have properties that may be especially beneficial in xenotransplantation. These include suppression of T cell proliferation, increases in the number of T regulatory cells, inhibition of pig graft growth, and anti-inflammatory, anti-viral, and anti-cancer effects. We here review the potential benefits and risks of mTOR-Is in xenotransplantation and suggest that the benefits exceed the adverse effects.

Molecular and therapeutic insights of rapamycin: a multi-faceted drug from Streptomyces hygroscopicus

The advancement in pharmaceutical research has led to the discovery and development of new combinatorial life-saving drugs. Rapamycin is a macrolide compound produced from Streptomyces hygroscopicus. Rapamycin and its derivatives are one of the promising sources of drug with broad spectrum applications in the medical field. In recent times, rapamycin has gained significant attention as of its activity against cytokine storm in COVID-19 patients. Rapamycin and its derivatives have more potency when compared to other prevailing drugs. Initially, it has been used exclusively as an anti-fungal drug. Currently rapamycin has been widely used as an immunosuppressant. Rapamycin is a multifaceted drug; it has anti-cancer, anti-viral and anti-aging potentials. Rapamycin has its specific action on mTOR signaling pathway. mTOR has been identified as a key regulator of different pathways. There will be an increased demand for rapamycin, because it has lesser adverse effects when compared to steroids. Currently researchers are focused on the production of effective rapamycin derivatives to combat the growing demand of this wonder drug. The main focus of the current review is to explore the origin, development, molecular mechanistic action, and the current therapeutic aspects of rapamycin. Also, this review article revealed the potential of rapamycin and the progress of rapamycin research. This helps in understanding the exact potency of the drug and could facilitate further studies that could fill in the existing knowledge gaps. The study also gathers significant data pertaining to the gene clusters and biosynthetic pathways involved in the synthesis and production of this multi-faceted drug. In addition, an insight into the mechanism of action of the drug and important derivatives of rapamycin has been expounded. The fillings of the current review, aids in understanding the underlying molecular mechanism, strain improvement, optimization and production of rapamycin derivatives.

Current status of xenotransplantation research and the strategies for preventing xenograft rejection

Transplantation is often the last resort for end-stage organ failures, e.g., kidney, liver, heart, lung, and pancreas. The shortage of donor organs is the main limiting factor for successful transplantation in humans. Except living donations, other alternatives are needed, e.g., xenotransplantation of pig organs. However, immune rejection remains the major challenge to overcome in xenotransplantation. There are three different xenogeneic types of rejections, based on the responses and mechanisms involved. It includes hyperacute rejection (HAR), delayed xenograft rejection (DXR) and chronic rejection. DXR, sometimes involves acute humoral xenograft rejection (AHR) and cellular xenograft rejection (CXR), which cannot be strictly distinguished from each other in pathological process. In this review, we comprehensively discussed the mechanism of these immunological rejections and summarized the strategies for preventing them, such as generation of gene knock out donors by different genome editing tools and the use of immunosuppressive regimens. We also addressed organ-specific barriers and challenges needed to pave the way for clinical xenotransplantation. Taken together, this information will benefit the current immunological research in the field of xenotransplantation.

First-in-human phase 1 trial of induced regulatory T cells for graft-versus-host disease prophylaxis in HLA-matched siblings

Human CD4+25- T cells cultured in interleukin 2 (IL-2), rapamycin, and transforming growth factor β (TGFβ) along with anti-CD3 monoclonal antibody-loaded artificial antigen-presenting cells generate FoxP3+ induced regulatory T cells (iTregs) with potent suppressive function. We performed a phase 1, single-center, dose-escalation study to determine the safety profile of iTregs in adults with high-risk malignancy treated with reduced-intensity conditioning and mobilized peripheral blood stem cells (PBSCs) from HLA-identical sibling donors. Sixteen patients were enrolled and 14 were treated (2 productions failed to meet desired doses). One patient each received 3.0 × 106/kg, 3.0 × 107/kg, and 3.0 × 108/kg iTregs with corresponding T-conventional-to-iTreg ratios of 86:1, 8:1, and 1:2. After 3 patients received 3.0 × 108/kg in the presence of cyclosporine (CSA) and mycophenolate mofetil (MMF) with no dose-limiting toxicities, subsequent patients were to receive iTregs in the presence of sirolimus/MMF that favors Foxp3 stability based on preclinical modeling. However, 2 of 2 developed grade 3 acute graft-versus-host disease (GVHD), resulting in suspension of the sirolimus/MMF. An additional 7 patients received 3.0 × 108/kg iTregs with CSA/MMF. In the 14 patients treated with iTregs and CSA/MMF, there were no severe infusional toxicities with all achieving neutrophil recovery (median, day 13). Of 10 patients who received 3.0 × 108/kg iTregs and CSA/MMF, 7 had no aGVHD, 2 had grade 2, and 1 had grade 3. Circulating Foxp3+ iTregs were detectable through day 14. In summary, iTregs in the context of CSA/MMF can be delivered safely at doses as high as 3 × 108/kg. This trial was registered at www.clinicaltrials.gov as #NCT01634217.

Heterotopic Porcine Cardiac Xenotransplantation in the Intra-Abdominal Position in a Non-Human Primate Model

Heterotopic cardiac transplantation in the intra-abdominal position in a large animal model has been essential in the progression of the field of cardiac transplantation. Our group has over 10 years of experience in cardiac xenotransplantation with pig to baboon models, the longest xenograft of which survived over 900 days, with rejection only after reducing immunosuppression. This article aims to clarify our approach to this model in order to allow others to share success in long-term survival. Here, we demonstrate the approach to implantation of a cardiac graft into the intra-abdominal position in a baboon recipient for the study of transplantation and briefly highlight our model's ability to provide insight into not only xenotransplantation but across disciplines. We include details that have provided us with consistent success in this model; performance of the anastomoses, de-airing of the graft, implantation of a long-term telemetry device for invasive graft monitoring, and ideal geometric positioning of the heart and telemetry device in the limited space of the recipient abdomen. We additionally detail surveillance techniques to assess long-term graft function.

A novel and effective method to generate human porcine-specific regulatory T cells with high expression of IL-10, TGF-β1 and IL-35

Organ transplantation remains the most effective treatment for patients with late stage organ failure. Transgenic pigs provide an alternative organ donor source to the limited availability of human organs. However, cellular rejection still remains to be the obstacle for xenotransplantation. Superior to other methods, antigen-specific regulatory T cells (Treg) alleviate cellular rejection with fewer side effects. Here we demonstrate the use of a fast method to provide tolerogenic dendritic cells (tolDC) that can be used to generate effective porcine-specific Treg cells (PSTreg). TolDC were produced within three days from human monocytes in medium supplemented with anti-inflammatory cytokines. Treg were generated from naïve CD4⁺ T cells and induced to become PSTreg by cocultivation with porcine-antigen-loaded tolDC. Results showed that PSTreg exhibited the expected phenotype, CD4⁺CD25⁺CD127^low/− Foxp3⁺, and a more activated phenotype. The specificity of PSTreg was demonstrated by suppression of effector T cell (Teff) activation markers of different stages and inhibition of Teff cell proliferation. TolDC and PSTreg exhibited high expression of IL-10 and TGF-β1 at both protein and RNA levels, and PSTreg also highly expressed IL-35 at RNA levels. Upon restimulation, PSTreg retained the activated phenotype and specificity. Taken together, the newly developed procedure allows efficient generation of highly suppressive PSTreg.

Missed, Not Missing: Phylogenomic Evidence for the Existence of Avian FoxP3

The Forkhead box transcription factor FoxP3 is pivotal to the development and function of regulatory T cells (Tregs), which make a major contribution to peripheral tolerance. FoxP3 is believed to perform a regulatory role in all the vertebrate species in which it has been detected. The prevailing view is that FoxP3 is absent in birds and that avian Tregs rely on alternative developmental and suppressive pathways. Prompted by the automated annotation of foxp3 in the ground tit (Parus humilis) genome, we have questioned this assumption. Our analysis of all available avian genomes has revealed that the foxp3 locus is missing, incomplete or of poor quality in the relevant genomic assemblies for nearly all avian species. Nevertheless, in two species, the peregrine falcon (Falco peregrinus) and the saker falcon (F. cherrug), there is compelling evidence for the existence of exons showing synteny with foxp3 in the ground tit. A broader phylogenomic analysis has shown that FoxP3 sequences from these three species are similar to crocodilian sequences, the closest living relatives of birds. In both birds and crocodilians, we have also identified a highly proline-enriched region at the N terminus of FoxP3, a region previously identified only in mammals.

Dynamic Metabolism in Immune Response

Cell, the basic unit of life depends for its survival on nutrients and thereby energy to perform its physiological function. Cells of lymphoid and myeloid origin are key in evoking an immune response against "self" or "non-self" antigens. The thymus derived lymphoid cells called T cells are a heterogenous group with distinct phenotypic and molecular signatures that have been shown to respond against an infection (bacterial, viral, protozoan) or cancer. Recent studies have unearthed the key differences in energy metabolism between the various T cell subsets, natural killer cells, dendritic cells, macrophages and myeloid derived suppressor cells. While a number of groups are dwelling into the nuances of the metabolism and its role in immune response at various strata, this review focuses on dynamic state of metabolism that is operational within various cellular compartments that interact to mount an effective immune response to alleviate disease state.

Adoptive transfusion of tolerogenic dendritic cells prolongs the survival of liver allograft: a systematic review

OBJECTIVES

To systematically review the effects of tolerogenic dendritic cells (Tol-DCs) induced by different methods on liver transplantation and their possible mechanisms of action.

METHODS

PubMed and EMbase were searched for relevant articles through 31 December 2013. The effects of Tol-DCs on liver allograft survival were semiquantitatively evaluated, and the possible mechanisms by which Tol-DCs prolong graft survival were analyzed.

RESULTS

Seven articles were included, and classified according to methods of induction, sources, and methods of infusing Tol-DCs. Tol-DCs induced from immature DCs (imDCs), with cytokines, and by gene modification induced liver transplant tolerance for 33.1 ± 32.5 days (2.7-fold vs. control), 26.17 ± 16.20 days (1.8-fold vs. control), and 11.7 ± 1.6 days (2.3-fold vs. control), respectively. DCs derived from recipient bone marrow, donor bone marrow, and donor spleen induced liver transplant tolerance for 51.0 ± 0.0 days (5.9-fold vs. control), 21.4 ± 26.8 days (2.4-fold vs. control), and 15.0 ± 0.0 days (2.3-fold vs. control), respectively. The primary mechanisms by which Tol-DCs induce liver transplant tolerance were the induction of T-cell hyporeactivity and Th2 differentiation.

CONCLUSIONS

Tol-DCs induced by three different methods could extend liver allograft survival, with imDCs showing optimal results. The optimal infusion method was intravenous injection of 1-2 × 10(6) Tol-DC, similar to findings in renal transplantation. Tol-DCs prolonged liver transplant tolerance more than renal transplant tolerance.

Ex-vivo expanded baboon CD4+ CD25 Hi Treg cells suppress baboon anti-pig T and B cell immune response

BACKGROUND

CD4(+) CD25(+) FoxP3(+) regulatory T (Treg) cells play an important role in regulating immune responses. A very small number of Treg cells are present in peripheral blood and lymphoid organs, but due to their ability to suppress the immune response, they have a high potential for immunotherapy in clinics. Successful ex-vivo expansion of naturally occurring CD4(+) CD25(+) T cells has been achieved after TCR stimulation in the presence of T cell growth factors. In this study, we evaluated the role of these Treg cells in suppressing proliferative response of baboon T and B cells to pig xenoantigens.

METHODS

Naturally occurring baboon CD4(+) CD25(+) regulatory T cells (nTreg) were sorted from peripheral blood and expanded in the presence of either anti-CD3/CD28 beads or irradiated pig peripheral blood mononuclear cells with IL-2. Treg cells were also enriched directly from CD4(+) T cells cultured in the presence of rapamycin (0.1-10 nm). Mixed lymphocyte culture and polyclonal B cell stimulation with ex-vivo Treg cells were performed to assess the function of ex-vivo expanded Treg cells.

RESULTS

The nTreg cells were expanded to more than 200-fold in 4 weeks and retained all the nTreg cell phenotypic characteristics, including high levels of FoxP3 expression. 2-fold increase in enrichment of CD4(+) CD25(+) FoxP3(+) Treg cells from CD4(+) cells was observed with rapamycin compared to cultures without rapamycin. The ex-vivo expanded Treg cells obtained from both methods were able to suppress the baboon anti-porcine xenogeneic T and B cell immune response in-vitro efficiently (more than 90% suppression at 1:1 ratio of T regulatory cells: T effector cells), and their suppression potential was retained even at 1:256 ratio. However, freshly isolated nTreg cells had only 70% suppression at 1:1 ratio, and their suppressive ability was reduced to ≤ 50% at 1:16 ratio. Furthermore, we have found that ex-vivo expanded Treg can also suppress the proliferation of B cells after polyclonal stimulation. Forty to 50 percent reduction in B cell proliferation was observed when ex-vivo expanded Treg cells were added to the culture at a 1:1 ratio. The addition of CD4(+) CD25(Neg) cells however induced vigorous proliferation.

CONCLUSION

Ex-vivo expanded CD4(+) CD25(+) FoxP3(+) Treg cells can be used to efficiently suppress xenogeneic immune responses by inhibiting T and B cell proliferation. These ex-vivo expanded Treg cells may also be used with other immunosuppressive agents to overcome xenograft rejection in preclinical xenotransplantation models.

Immunohistochemical investigation of Foxp3 expression in the intestine in healthy and diseased dogs

Intestinal immune regulation including development of oral tolerance is of great importance for the maintenance of intestinal homeostasis. Concerning this, regulatory T cells (Tregs) occupy a pivotal role in cell-mediated immunosuppression. Dysregulation of mucosal immunology leading to an abnormal interaction with commensal bacteria is suggested to play a key role in the pathogenesis of Inflammatory Bowel Disease (IBD) in men and dogs. The aim of this study was to characterise the expression of Foxp3 in the normal canine gut of 18 dogs (mean age: 6.03 years), in 16 dogs suffering from IBD (mean age: 5.05 years), and of 6 dogs with intestinal nematode infection (mean age: 0.87 years) using immunohistochemistry. In the duodenum, Tregs in healthy dogs declined from villi (median: 10.67/62 500 μm2) to crypts (median: 1.89/62 500 μm2). Tregs were further increased in the villi of middle-aged dogs (median: 18.92/62 500 μm2) in contrast to juvenile (median: 3.50/62 500 μm2) and old (median: 9.56/62 500 μm2) individuals. Compared to healthy controls, animals suffering from IBD revealed reduced numbers of Tregs in duodenal villi (median: 4.13/62 500 μm2). Dogs with intestinal nematode infection displayed increased numbers of Tregs (median: 21.06/62 500 μm2) compared to healthy animals.Age-related changes indicate a progressive establishment of oral tolerance and immunosenescence in the canine elderly. The results further suggest that a defect in Treg homeostasis may be involved in the pathogenesis of canine IBD. In contrast, increased numbers of Tregs in the duodenum may be due to nematode infection.

Rapamycin combined with donor immature dendritic cells promotes liver allograft survival in association with CD4(+) CD25(+) Foxp3(+) regulatory T cell expansion

AIM

  To determine whether donor immature dendritic cells (imDCs) combined with a short postoperative course of rapamycin (Rapa) has the ability to expand the CD4(+) CD25(+) Foxp3(+) regulatory T (Treg) cells and prolong liver allograft survival.

METHODS

  Orthotopic liver transplantation (OLT) was performed from Lewis rats to Brown Norway recipients. Three days before transplantation, animals were injected intravenously with 2 × 10(6) donor bone marrow-derived imDCs. Recipient rats (the combined treated group) also received Rapa for 7 d after liver transplantation. Additional groups received either imDCs alone, Rapa alone, or saline alone. Every six recipients from each group were killed at 14 days, 28 days after OLT. The changes of CD4(+) CD25(+) Foxp3(+) Treg cells in peripheral blood and spleen, histological changes of liver grafts, and serum cytokine levels were investigated. The other six recipients were left in each group to observe the animal survival.

RESULTS

  Donor imDCs followed by a short postoperative course of Rapa induced long-term allograft survival. The percentage of CD4(+) CD25(+) Foxp3(+) Treg cells in CD4(+) T cells in the combination treatment group were significantly higher compared with the acute rejection group. Moreover, within the CD4(+) CD25(+) T cell population the combination treatment recipients maintained a higher incidence of Foxp3(+) T cells compared with the other groups. Despite the lower serum levels of interleukin (IL)-2, IL-12, and interferon-γ in the combined treated group, the cytokine levels in the combined treated group at 7 days after OLT was nearly twice that at 3 days after OLT but decreased significantly compared with the other groups at 28 days after OLT. Serum IL-10 level in the combined treated group was higher than the other groups.

CONCLUSIONS

  A single imDC infusion followed by a short postoperative course of Rapa prolongs liver allograft survival and enhances the expansion of Treg cells. This optimal protocol may be a promising administration protocol for the peritransplant tolerance induction.

Induced regulatory T cells: mechanisms of conversion and suppressive potential

Thymus-derived, naturally occurring CD4(+) Forkhead Box P3(+) regulatory T cells (nTreg) have suppressive activity that is important for the establishment and maintenance of immune homeostasis in the healthy state. Abundant reports have demonstrated that they can suppress pathogenic processes in autoimmune diseases and inhibit transplant rejection and graft-versus-host disease. Far less is known about induced regulatory T cells (iTreg) that are generated from naive T cells in the periphery or in vitro by directing naive T cells to acquire suppressive function under the influence of transforming growth factor-β and other factors. In this review, we describe mechanisms by which naive T cells are thought to be converted into iTreg. We also discuss the suppressive potential of iTreg, particularly in comparison with their naturally occurring counterparts, focusing on those reports in which direct comparisons have been made. Based on current knowledge, we consider the rationale for using iTreg versus nTreg in clinical trials.

Infusion of ex vivo expanded T regulatory cells in adults transplanted with umbilical cord blood: safety profile and detection kinetics

Acute graft-versus-host disease (aGVHD) is associated with high risk of morbidity and mortality and is a common complication after double umbilical cord blood (UCB) transplantation. To reduce these risks, we established a method of CD4(+)CD25(+)FoxP3(+) T regulatory cell (Treg) enrichment from cryopreserved UCB followed by a 18 (+) 1-day expansion culture including anti-CD3/anti-CD28 antibody-coated beads and recombinant human interleukin-2. In a "first-in-human" clinical trial, we evaluated the safety profile of UCB Treg in 23 patients. Patients received a dose of 0.1-30 × 10(5)UCB Treg/kg after double UCB transplantation. The targeted Treg dose was achieved in 74% of cultures, with all products being suppressive in vitro (median 86% suppression at a 1:4 ratio). No infusional toxicities were observed. After infusion, UCB Treg could be detected for 14 days, with the greatest proportion of circulating CD4(+)CD127(-)FoxP3(+) cells observed on day (+)2. Compared with identically treated 108 historical controls without Treg, there was a reduced incidence of grade II-IV aGVHD (43% vs 61%, P = .05) with no deleterious effect on risks of infection, relapse, or early mortality. These results set the stage for a definitive study of UCB Treg to determine its potency in preventing allogeneic aGVHD. This study is registered at http://www.clinicaltrials.gov as NCT00602693.

Phenotypic and functional characterization of a CD4(+) CD25(high) FOXP3(high) regulatory T-cell population in the dog

Relatively little is known about regulatory T (Treg) cells and their functional responses in dogs. We have used the cross-reactive anti-mouse/rat Foxp3 antibody clone FJK-16s to identify a population of canine CD4(+) FOXP3(high) T cells in both the peripheral blood (PB) and popliteal lymph node (LN). FOXP3(+) cells in both PB and LN yielded positive staining with the newly developed anti-murine/human Helios antibody clone 22F6, consistent with the notion that they were naturally occurring Treg cells. Stimulation of mononuclear cells of LN origin with concanavalin A (Con A) in vitro yielded increased proportions and median fluorescence intensity of FOXP3 expression by both CD4(+) and CD8(+) T cells. Removal of the Con A and continued culture disclosed a CD4(+)  FOXP3(high) population, distinct from the CD4(+) FOXP3(intermediate) T cells; very few CD8(+) FOXP3(high) T cells were observed, though CD8(+) FOXP3(intermediate) cells were present in equal abundance to CD4(+) FOXP3(intermediate) cells. The CD4(+)  FOXP3(high) T cells were thought to represent activated Treg cells, in contrast to the FOXP3(intermediate) cells, which were thought to be a more heterogeneous population comprising predominantly activated conventional T cells. Co-staining with interferon-γ (IFN-γ) supported this notion, because the FOXP3(high) T cells were almost exclusively IFN-γ(-) , whereas the FOXP3(intermediate) cells expressed a more heterogeneous IFN-γ phenotype. Following activation of mononuclear cells with Con A and interleukin-2, the 5% of CD4(+) T cells showing the highest CD25 expression (CD4(+) CD25(high) ) were enriched in cells expressing FOXP3. These cells were anergic in vitro, in contrast to the 20% of CD4(+) T cells with the lowest CD25 expression (CD4(+) CD25(-) ), which proliferated readily. The CD4(+) CD25(high) FOXP3(high) T cells were able to suppress the proliferation of responder CD4(+) T cells in vitro, in contrast to the CD4(+) CD25(-) cells, which showed no regulatory properties.

The effects of immunosuppressive drugs on CD4(+) CD25(+) regulatory T cells: a systematic review of clinical and basic research

OBJECTIVE

To review the effects of different immunosuppressive drugs on proliferation and function of regulatory T cells (Tregs).

METHODS

We searched MEDLINE, Embase (from inception to September 2009), and the Cochrane Library (Issue 4, 2009) for clinical and basic research about the effects of various immunosuppressive drugs on Tregs. Data were extracted and methodological quality was assessed by two independent reviewers. Outcome measures for clinical research included blood Tregs levels, acute rejection episodes, and graft function. Outcomes for basic research included percentage of Tregs proliferation, function, Tregs phenotype, and evidence for possible mechanisms. We analyzed data qualitatively.

RESULTS

Forty-two studies, including 19 clinical trials and 23 basic studies, were included. The immunosuppressive drugs studied were calcineurin inhibitors (CNIs), Rapa, anti-metabolism drugs, IL-2 receptor-blocking antibodies, T-cell depleting antibodies, and co-stimulation blockade antibodies. Most of the studies were on Rapa and CNIs. Eight basic studies on Rapa and CNIs showed that Rapa could promote the proliferation and function of Tregs, while CNIs could not. Five clinical trials involving a total of 158 patients showed that patients taking Rapa had higher blood concentration of Tregs than patients taking CNIs, but no difference was found in graft function (6-42 months follow-up).

CONCLUSION

There is substantial evidence that Rapa favors Tregs survival and function. However, the higher numbers of blood Tregs in patients treated with Rapa do not show any association with better graft function. Larger clinical studies with longer follow-up are needed to more thoroughly assess the efficacy of immunosuppressive drugs on Tregs, and reveal whether a relationship exists between Tregs and graft function.