Role and mechanisms of CD4+CD25+ regulatory T cells in the induction and maintenance of transplantation tolerance

Emerging hallmark of gliomas microenvironment in evading immunity: a basic concept

Background

Over the last decade, since clinical trials examining targeted therapeutics for gliomas have failed to demonstrate a meaningful increase in survival, the emphasis has recently been switched toward innovative techniques for modulating the immune response against tumors and their microenvironments (TME). Cancerous cells have eleven hallmarks which make it distinct from normal ones, among which is immune evasion. Immune evasion in glioblastoma helps it evade various treatment modalities.

Summary

Glioblastoma’s TME is composed of various array of cellular actors, ranging from peripherally derived immune cells to a variety of organ-resident specialized cell types. For example, the blood–brain barrier (BBB) serves as a selective barrier between the systemic circulation and the brain, which effectively separates it from other tissues. It is capable of blocking around 98% of molecules that transport different medications to the target tumor.

Objectives

The purpose of this paper is to offer a concise overview of fundamental immunology and how ‘clever’ gliomas avoid the immune system despite the discovery of immunotherapy for glioma.

Conclusions

Herein, we highlight the complex interplay of the tumor, the TME, and the nearby normal structures makes it difficult to grasp how to approach the tumor itself. Numerous researchers have found that the brain TME is a critical regulator of glioma growth and treatment efficacy.

Helper T Cells in Idiopathic Membranous Nephropathy

Idiopathic membranous nephropathy (IMN) is an autoimmune disease in which the immune system produces an antibody response to its own antigens due to impaired immune tolerance. Although antibodies are derived from plasma cells differentiated by B cells, the T-B cells also contribute a lot to the immune system. In particular, the subsets of helper T (Th) cells, including the dominant subsets such as Th2, Th17, and follicular helper T (Tfh) cells and the inferior subsets such as regulatory T (Treg) cells, shape the immune imbalance of IMN and promote the incidence and development of autoimmune responses. After reviewing the physiological knowledge of various subpopulations of Th cells and combining the existing studies on Th cells in IMN, the role model of Th cells in IMN was explained in this review. Finally, the existing clinical treatment regimens for IMN were reviewed, and the importance of the therapy for Th cells was highlighted.

Vitamin C as a Supplementary Therapy in Relieving Symptoms of the Common Cold: A Meta-Analysis of 10 Randomized Controlled Trials

Aim

To investigate whether vitamin C performs well as a supplemental treatment for common cold.

Method

After systematically searching through the National Library of Medicine (PubMed), Cochrane Library, Elsevier, China National Knowledge Infrastructure (CNKI), VIP databases, and Wanfang databases, 10 randomized controlled trials were selected for our meta-analysis with RevMan 5.3 software. Published in China, all 10 studies evaluated the effect of combined vitamin C and antiviral therapy for the treatment of common cold.

Results

The total efficacy (RR = 1.27, 95% CI (1.08, 1.48), P = 0.003), the time for symptom amelioration (MD = −15.84, 95% CI (-17.02, -14.66), P < 0.00001), and the time for healing (I, 95% CI (-14.98, -4.22), P = 0.0005) were better with vitamin C supplementation than with antiviral therapy alone.

Conclusions

Vitamin C could be used as a supplementary therapy along with antiviral regimens to relieve patients from the symptoms of common cold.

High Expression of FOXP3 mRNA in Blood and Urine as a Predictive Marker in Kidney Transplantation

BACKGROUND

Diagnosis of allograft dysfunction by noninvasive biomarker tests is preferable to invasive allograft biopsies and has been extensively considered in recent years. This study aims to evaluate blood and urinary forkhead box P3 (FOXP3) messenger RNA (mRNA) expression in renal transplant recipients in an attempt to determine whether differential diagnosis of graft dysfunction is feasible using mRNA profiles.

METHODS

We analyzed FOXP3 mRNA expression in paired urinary and peripheral blood mononuclear cell (PBMC) samples. A total of 91 kidney transplant recipients enrolled in this study that were classified into 3 groups: biopsy-proven acute rejection (AR; n = 27), chronic allograft nephropathy (n = 19), and well-functioning graft (n = 45). The FOXP3 mRNA expression was quantified by TaqMan probe real-time polymerase chain reaction.

RESULTS

Acute rejection patients had a higher expression level of transcription factor FOXP3 compared to the chronic nephropathy and control groups. Analysis of receiver operating characteristic curves showed that rejection could be diagnosed with 100% sensitivity and 96% specificity in urine, and 92% sensitivity and 86% specificity in PBMC samples using the optimal FOXP3 mRNA cutoff value. We subdivided the AR group into progressive and nonprogressive patients, which showed a significant difference in FOXP3 mRNA expression. This result confirmed the role of FOXP3 as a diagnostic marker in predicting transplantation outcomes.

CONCLUSION

Our results suggested that elevated expression of FOXP3 in blood and urine samples from kidney transplant recipients could be a useful noninvasive biomarker to diagnose graft dysfunction.

Transforming Growth Factor-β Partially Reversed the Immunosuppressive Effect of Mesenchymal Stem Cells in Mice

BACKGROUND

Mesenchymal stem cells (MSCs) possess powerful immunosuppression capacity. Transforming growth factor-β (TGF-β) is a well-known anti-inflammatory cytokine and plays an important role in various inflammatory processes. We hypothesized that TGF-β could synergize with MSCs in suppressing immune responses, and therefore established a mouse skin graft model to evaluate the effect of MSCs and MSCs combined with TGF-β on transplantation immunity in vivo.

METHODS

Balb/c and C57BL/6 mice were used to establish the skin graft model. The recipients were divided into 3 groups and received intravenous bone marrow mesenchymal stem cells (BMSCs), BMSCs pretreated with TGF-β, and 0.9% saline solution, respectively. Skin graft survival time, pathological detection, the ratio of CD4+CD25+Foxp3+Treg cell of spleens, and the level of IFN-γ, IL-2, IL-10, and TGF-β expression were tested.

RESULTS

The survival time of skin grafts were prolonged in both BMSC (12.5 ± 1.35 days) and BMSC-TGF-β (10.6 ± 1.90 days) recipients compared to the blank control recipients (8.0 ± 1.05 days). The ratio of CD4+CD25+Foxp3+Treg cell of spleens from BMSC and BMSC-TGF-β recipients was higher than that of the blank control, and the upregulated proliferation in the BMSC group occurred earlier and was prolonged compared to the BMSC-TGF-β group. The expression of IFN-γ and IL-2 was inhibited in both the BMSC and BMSC-TGF-β groups compared to the blank, while the expression of IL-10 and TGF-β was boosted. In contrast to the BMSC group, the BMSC-TGF-β group exhibited a weaker effect on the expression of cytokines.

CONCLUSION

TGF-β partially reversed the immunosuppressive effect of MSCs in vivo. This immunoregulatory feature may have potential applications for treating transplant rejection.

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.

Immunologic Monitoring to Personalize Immunosuppression After Liver Transplant

Although immunosuppressive drugs have enhanced patient outcomes in transplantation, the liver transplant community has made significant research efforts into the discovery of more accurate and precise methods of posttransplant monitoring and diagnosing. Current research in biomarkers reveals many promising approaches.

Tolerance in liver transplantation: Biomarkers and clinical relevance

Transplantation is the optimal treatment for end-stage organ failure, and modern immunosuppression has allowed important progress in short-term outcomes. However, immunosuppression poorly influences chronic rejection and elicits chronic toxicity in current clinical practice. Thus, a major goal in transplantation is to understand and induce tolerance. It is well established that human regulatory T cells expressing the transcription factor FoxP3 play important roles in the maintenance of immunological self-tolerance and immune homeostasis. The major regulatory T cell subsets and mechanisms of expansion that are critical for induction and long-term maintenance of graft tolerance and survival are being actively investigated. Likewise, other immune cells, such as dendritic cells, monocyte/macrophages or natural killer cells, have been described as part of the process known as "operational tolerance". However, translation of these results towards clinical practice needs solid tools to identify accurately and reliably patients who are going to be tolerant. In this way, a plethora of genetic and cellular biomarkers is raising and being validated worldwide in large multi-center clinical trials. Few of the studies performed so far have provided a detailed analysis of the impact of immunosuppression withdrawal on pre-existing complications derived from the long-term administration of immunosuppressive drugs and the side effects associated with them. The future of liver transplantation is aimed to develop new therapies which increase the actual low tolerant vs non-tolerant recipients ratio.

Tumor Necrosis Factor-α-Induced Protein 8-Like 2 Gene Overexpression Prolongs the Survival of Rat Allogeneic Heart Allografts

BACKGROUND

The objective of the study was to examine whether overexpression of the tumor necrosis factor-α-induced protein 8-like 2 (TNFAIP8L2; TP8L2) gene might prolong the survival of a rat heart allograft and to explore the possibility of gene-induced immune tolerance and its specific mechanisms of action in rats.

METHODS

A gene vector (AdC68) was constructed of a rat's TP8L2 gene to overexpress the TP8L2 gene in the models. The Wistar-to-Dawley rat allogeneic heart allograft models were created and randomly separated into 5 groups: control, no treatment after surgery; Fk506, treated with immune inhibitor FK506 0.5 mg/kg/d after surgery; TP8L2, treated with 0.25 × 10(9) Pfu recombinant TP8L2 adenovirus after surgery; FK506+TP8L2, treated with FK506 0.25 mg/kg/d and 0.25 × 10(9) Pfu recombinant TP8L2 adenovirus after surgery; and no-TP8L2, treated with 0.25 × 10(9) Pfu recombinant adenovirus without TP8L2 gene overexpression after surgery. We also examined whether the overexpressed TP8L2 gene can prolong the donor heart's mean survival time and detect the changes of various related indicators.

RESULTS

The survival time of the donor heart in the TP8L2 and FK506+TP8L2 groups was significantly longer than that in the remaining groups; the difference was statistically significant (P < .05). The percentage of CD4(+)CD25(+) regulatory T cells in the TP8L2 and FK506+TP8L2 groups was significantly higher than that in the remaining groups; the difference was statistically significant (P < .05). The expression of interleukin (IL)-2, tumor necrosis factor-α, and interferon-γ in the FK506+TP8L2 group was significantly lower and the expression of IL-4 and IL-10 was significantly higher than those in other groups; the differences in cytokine levels were significant (P < .05).

CONCLUSIONS

TP8L2 plays an important role in the induction of immune tolerance in heart allografts.

Epidemiology

More than 250,000 new cases of primary malignant brain tumors are diagnosed annually worldwide, 77% of which are gliomas. A small proportion of gliomas are caused by the inheritance of rare high-penetrance genetic variants or high-dose radiation. Since 2009, inherited genetic variants in 10 regions near eight different genes have been consistently associated with glioma risk via genome-wide association studies. Most of these variants increase glioma risk by 20-40%, but two have higher relative risks. One on chromosome 8 increases risk of IDH-mutated gliomas sixfold and another that affects TP53 function confers a 2.5-fold increased risk of glioma. Functions of some of the other risk variants are known or suspected, but future research will determine functions of other risk loci. Recent progress also has been made in defining subgroups of glioma based on acquired alterations within tumors. Allergy history has been consistently associated with reduced glioma risk, though the mechanisms have not yet been clarified. Future studies will need to be large enough so that environmental and constitutive genetic risk factors can be examined within molecularly defined, etiologically homogeneous subgroups.

Elevated miR-155 expression induces immunosuppression via CD39(+) regulatory T-cells in sepsis patient

BACKGROUND

An altered microRNA profile exists in many infectious diseases, including sepsis. CD39(+) regulatory T-cells (Tregs) have a remarkable immunosuppressive effect and play an important role in the regulation of immune balance in sepsis. However, the correlation between microRNA changes and the ratio of CD39(+) Tregs in sepsis patients has not yet been reported. The altered microRNA expression profile in sepsis patients was analyzed in this study. Moreover, the correlation between microRNAs and disease severity and prognosis was investigated. Furthermore, the correlation between microRNAs and the percentage of peripheral blood CD39(+) Tregs was investigated and further verified in an animal model.

METHODS

Sixty sepsis patients and 30 healthy controls were included. The difference in microRNA expression was investigated by microRNA microarray and was further confirmed by real-time quantitative PCR. The correlations between microRNA changes and the Sepsis-related Organ Failure Assessment (SOFA) score, severity of sepsis, and survival were analyzed. The percentage CD39(+) Tregs in the peripheral blood of sepsis patients was measured by flow cytometry. The correlation between microRNAs and the percentage CD39(+) Tregs was analyzed and further confirmed in a mouse sepsis model.

RESULTS

Compared to healthy controls, sepsis patients exhibited a significantly elevated microRNA-155 (miR-155) level (p < 0.05), which was positively related to a higher SOFA score (r = 0.641, p < 0.05) and a greater severity of sepsis. The area under the receiver operating characteristic curve of miR-155 used for the prediction of 28-day survival was 0.763, with a cut-off point of 2.47. Patients with a miR-155 level >2.47 had a lower 28-day survival (p < 0.05). The miR-155 level of patients was proportional to the percentage of CD39(+) Tregs (r = 0.637, p < 0.05). After transfection with miR-155 inhibitor, the ratio of CD39(+) Tregs in mice with sepsis was significantly reduced (p < 0.05).

CONCLUSIONS

A higher level of miR-155 indicated a more severe condition and poorer prognosis in sepsis patients. The possible underlying mechanism could be that miR-155 induces an increased percentage of CD39(+) Tregs and thus immunosuppression.

Inhibition of the interleukin-6 signaling pathway: a strategy to induce immune tolerance

Interleukin-6 (IL-6) is a proinflammatory cytokine that is multifunctional, with multifaceted effects. IL-6 signaling plays a vital role in the control of the differentiation and activation of T lymphocytes by inducing different pathways. In particular, IL-6 controls the balance between Th17 cells and regulatory T (Treg) cells. An imbalance between Treg and Th17 cells is thought to play a pathological role in various immune-mediated diseases. Deregulated IL-6 production and signaling are associated with immune tolerance. Therefore, methods of inhibiting IL-6 production, receptors, and signaling pathways are strategies that are currently being widely pursued to develop novel therapies that induce immune tolerance. This survey aims to provide an updated account of why IL-6 inhibitors are becoming a vital class of drugs that are potentially useful for inducing immune tolerance as a treatment for autoimmune diseases and transplant rejection. In addition, we discuss the effect of targeting IL-6 in recent experimental and clinical studies on autoimmune diseases and transplant rejection.

Time elapsed after transplantation influences the relationship between the number of regulatory T cells in lung allograft biopsies and subsequent acute rejection episodes

BACKGROUND

Regulatory T lymphocytes (Tregs) play an important role in acute rejection after lung transplantation. However, the importance of the time elapsed after transplantation on the Treg response requires further investigation. We aim to evaluate the change over time in the frequency of Tregs in lung allograft biopsies and to assess how Tregs relate to simultaneous and subsequent acute cellular rejection.

MATERIALS AND METHODS

A total of 258 biopsy samples obtained 0.5, 1, 3, 12 and 24 months after transplantation from 58 consecutive lung transplant patients were included. The biopsies were scored for acute rejection according to the ISHLT criteria (A0-A4) and immunohistochemically stained with antibodies against FoxP3.

RESULTS

There was a tendency for a decrease in the number of Tregs/mm2 with time. However, the previous levels of Tregs/mm2 did not have any significant effect on future levels of Tregs/mm2. For biopsies taken 0.5 and 1 month after transplantation, a significant correlation between Tregs/mm2 and the degree of acute rejection was found, and logistic regression analysis using updated values for Tregs/mm2 showed a significant relationship between Tregs/mm2 at 2 weeks and an A-score≥2 after 1 and 3 months. At later time points, this correlation disappeared.

DISCUSSION AND CONCLUSION

Our data indicate that the time elapsed after transplantation is an important parameter influencing the Treg response after lung transplantation. This observation is in accordance with studies indicating a narrow therapeutic window for induction of tolerance by specifically targeting T-cells. The results also indirectly indicate that Tregs early after transplantation could have an impact on the long-term outcome.

CD8+ CD122+ regulatory T cells contain clonally expanded cells with identical CDR3 sequences of the T-cell receptor β-chain

We identified CD8(+)  CD122(+) regulatory T cells (CD8(+)  CD122(+) Treg cells) and reported their importance in maintaining immune homeostasis. The absence of CD8(+)  CD122(+) Treg cells has been shown to lead to severe systemic autoimmunity in several mouse models, including inflammatory bowel diseases and experimental autoimmune encephalomyelitis. The T-cell receptors (TCRs) expressed on CD8(+)  CD122(+) Treg cells recognize the target cells to be regulated. To aid in the identification of the target antigen(s) recognized by TCRs of CD8(+)  CD122(+) Treg cells, we compared the TCR diversity of CD8(+)  CD122(+) T cells with that of conventional, naive T cells in mice. We analysed the use of TCR-Vβ in the interleukin 10-producing population of CD8(+)  CD122(+) T cells marked by high levels of CD49d expression, and found the significantly increased use of Vβ13 in these cells. Immunoscope analysis of the complementarity-determining region 3 (CDR3) of the TCR β-chain revealed remarkable skewing in a pair of Vβ regions, suggesting the existence of clonally expanded cells in CD8(+)  CD122(+) T cells. Clonal expansion in Vβ13(+) cells was confirmed by determining the DNA sequences of the CDR3s. The characteristic TCR found in this study is an important building block for further studies to identify the target antigen recognized by CD8(+)  CD122(+) Treg cells.

Regulatory T-cell subset analysis and profile of interleukin (IL)-10, IL-17 and interferon-gamma cytokine-producing cells in kidney allograft recipients with donor cells infusion

BACKGROUND

This pilot study aimed to assess whether the perioperative infusion of donor bone marrow cells (DBMC) in renal allograft recipients can affect the appearance of peripheral regulatory T-cell subsets and the profile of cytokine-producing cells [interferon-gamma (IFN-γ), interleukin (IL)-17 and IL-10] 2 years after transplantation.

METHODS

Fresh blood samples were collected from 14 kidney recipients who received infusion and from 13 kidney recipients without infusion who served as controls at the end of the second post-transplantation year. Initially the percentages of CD4(+)CD25(+)FoxP3(+) T cells and CD3(+)CD8(+)CD28(-) T cells were quantified using flowcytometry. Thereafter, the frequencies of IL-10-, IL-17- and IFN-γ-producing cells were determined separately using the ELISPOT technique with peptides corresponding to mismatched donor HLA-DR molecules and phytohemagglutinin (PHA).

RESULTS

The mean numbers of IFN-γ- and IL-17-producing cells in response to PHA were lower in infused patients than in controls (P = 0.02 and P = 0.18, respectively); however, an increased frequency of IL-10-producing cells was observed compared to controls (P = 0.07). Furthermore, the ratio of IL-10/IFN-γ-producing cells was significantly higher in the DBMC-infused group versus controls (P = 0.01). There was a negative correlation between the percentage of CD3(+)CD8(+)CD28(-)T cells and IL-17-producing cells in the infused group (r = -0.539, P = 0.04). The mean levels and the frequency of microchimerism within the first post-transplantation year were also significantly higher in infused patients than in controls (P = 0.007 and P = 0.001, respectively).

CONCLUSION

Our findings suggest that DBMC infusion could partially stimulate the regulatory mechanisms against alloimmune responses in kidney allograft recipients

Analysis of FOXP3 gene and protein expressions in renal allograft biopsies and their association with graft outcomes

BACKGROUND

The transcription factor FOXP3 is increased in acute renal rejection, but its influence on graft outcomes is unclear. This study correlated FOXP3 with dendritic cells and graft outcomes.

METHODS

We assessed 96 kidney transplants undergoing allograft biopsy for cause. FOXP3 mRNA was analyzed by real-time polymerase chain reaction (PCR) and FOXP3 protein and DCsCD83(+) by immunohistochemistry. Graft function and survival were assessed at 5 years post-transplantation, as well as by independent predictors of graft loss.

RESULTS

Intragraft FOXP3 gene and protein expression were significantly correlated (r = 0.541, p < 0.001). Both FOXP3 mRNA and protein were increased in patients with acute rejection (AR). High expression of FOXP3 mRNA or protein in biopsies did not correlate with clinical variables, but there was a trend to higher positive variation in the glomerular filtration rate (GFR) from biopsy to last follow-up. Patients with FOXP3-mRNA(high) had more DCsCD83(+) in biopsy, but these cells did not associate with AR. Five-year graft survival was not influenced by either FOXP3 mRNA or protein expressions.

CONCLUSIONS

FOXP3 mRNA and protein had a good correlation in archival renal graft tissue. Increased FOXP3 expression was found in AR and FOXP3 associated with high numbers of DCs. However, both FOXP3 mRNA and protein was not associated with better allograft outcomes.

CD28 superagonist antibody treatment attenuated obliterative bronchiolitis in rat allo-orthotopic tracheal transplantation by preferentially expanding Foxp3-expressing regulatory T cells

Obliterative airway disease (OAD) due to chronic alloantigen rejection remains a major challenge for long-term graft survival in lung transplantation. It is known that superagonistic CD28-specific monoclonal antibody JJ316 (supCD28 MAb) has the ability to induce regulatory T cells (Tregs) efficiently. Here we used a rat orthotopic tracheal transplantation model to investigate the effects of supCD28 MAb on expanding Tregs in vivo and its application in suppression of acute and chronic airway allograft rejection. SupCD28 MAb administration revealed a significant increase in the CD4+CD25+ T cells, CD4+FoxP3+ T cells, and CD4+CD25+ FoxP3+ T cells population among CD4+ T cells in spleen, peripheral blood, as well as cervical lymph nodes. The allografts from animals treated with supCD28 MAb showed significantly less airway obliteration and rejection of the respiratory epithelium compared with allografts of the mouse immunoglobulin G-treated group on the 5th day and the 60th day after transplantation. Overall, our data demonstrated that an intraperitoneally administrated low dose of supCD28 MAb was sufficient to induce Treg cell expansion in vivo and was effective in protecting the airway graft from early rejection and chronic OAD development. These findings provide the basis for new therapies to prevent OAD and perhaps rejection of allografts in other human transplantations.

Regulatory T cells: hypes and limitations

PURPOSE OF REVIEW

In recent years there has been increased interest in understanding the physiology and function of regulatory T cells. In this review we focus on the characterization of regulatory T-cell subsets and their potential therapeutic use in organ transplantation.

RECENT FINDINGS

Regulatory T cells can play an instrumental role in the establishment of operational tolerance to allografts. The level of expression and the extent of posttranslational acetylation of the regulatory T-cell specific transcription factor Foxp3 are important modulators of their suppressive activity. Low expression of CD127 can be used as a novel marker to define pure regulatory T-cell populations and the expression of CD45RA on CD4CD25 regulatory T cells characterizes a population with a more stable phenotype upon expansion in vitro. Interleukin-35 is a recently discovered immunosuppressive cytokine secreted by CD4CD25 regulatory T cells. Although the presence of allospecific memory T cells in the pretransplant period and the use of immunosuppressants might interfere with the effectiveness of regulatory T-cell-based therapies, encouraging results indicate that the immunosuppressive drug rapamycin does not affect the expansion and function of regulatory T cells and could be included in a combined therapy.

SUMMARY

Important advances have been made towards establishing regulatory T cells as a viable therapy in transplantation and the first clinical trials using human regulatory T cells are currently underway. There are, however, important limitations and safety issues that have to be addressed before this therapy can be fully translated into the clinic.

Ex vivo expansion of human Tregs by rabbit ATG is dependent on intact STAT3-signaling in CD4⁺ T cells and requires the presence of monocytes

The addition of low, nondepleting doses of rabbit antithymocyte globulin (ATG) to human peripheral blood mononuclear cells has been shown to expand functional CD4(+) CD25(+) FoxP3(+) regulatory T cells (Tregs) in vitro. This report is the first to elucidate the exact cellular mechanisms of ATG-mediated Treg expansion. CD4(+) T cells require monocytes, but not other antigen presenting cell subsets, to be present in coculture to expand Tregs. However, T cells do not require direct cell-cell contact with monocytes, suggesting the importance of soluble factors. Moreover, ATG initially "reprograms" CD4(+) T cells, but not monocytes, and induces STAT3 and STAT5 signaling in CD4(+) cells. These reprogrammed CD4(+) T cells subsequently secrete GM-CSF and IL-10 only in case of intact STAT3 signaling, which in turn promote the generation of tolerogenic CD14(+) CD11c(+) dendritic cells characterized by enhanced IL-10 and decreased IL-12 production. Treg expansion following ATG treatment is accompanied by enhanced gene expression of both GM-CSF and Bcl-2, but not TGF-β, in peripheral blood mononuclear cells. These results demonstrate that ex vivo expansion of human Tregs by ATG is due to its ability to reprogram CD4(+) T cells in a STAT3-dependent but TGF-β-independent manner, leading to the generation of monocyte-derived dendritic cells with a tolerogenic cytokine profile.

Prolonged renal allograft survival by donor interleukin-6 deficiency: association with decreased alloantibodies and increased intragraft T regulatory cells

Both humoral and cellular immune responses are involved in renal allograft rejection. Interleukin (IL)-6 is a regulatory cytokine for both B and Foxp3 (forkhead box P3)-expressing regulatory T (Treg) cells. This study was designed to investigate the impact of donor IL-6 production on renal allograft survival. Donor kidneys from IL-6 knockout (KO) vs. wild-type (WT) C57BL/6 mice (H-2b) were orthotopically transplanted to nephrotomized BALB/c mice (H-2d). Alloantibodies and Treg cells were examined by fluorescence-activated cell sorting analysis. Graft survival was determined by the time to graft failure. Here, we showed that a deficiency in IL-6 expression in donor kidneys significantly prolonged renal allograft survival compared with WT controls. IL-6 protein was upregulated in renal tubules and endothelium of renal allografts following rejection, which correlated with an increase in serum IL-6 compared with that in those receiving KO grafts or naive controls. The absence of graft-producing IL-6 or lower levels of serum IL-6 in the recipients receiving IL-6 KO allografts was associated with decreased circulating anti-graft alloantibodies and increased the percentage of intragraft CD4+CD25+Foxp3+ Treg cells compared with those with WT allografts. In conclusion, the lack of graft-producing IL-6 significantly prolongs renal allograft survival, which is associated with reduced alloantibody production and/or increased intragraft Treg cell population, implying that targeting donor IL-6 may effectively prevent both humoral and cellular rejection of kidney transplants.

Regulatory T-cells: diverse phenotypes integral to immune homeostasis and suppression

Regulatory T-cells (T(REG)) are diverse populations of lymphocytes that regulate the adaptive immune response in higher vertebrates. T(REG) delete autoreactive T-cells, induce tolerance, and dampen inflammation. T(REG) cell deficiency in humans (i.e., IPEX [Immunodysregulation, Polyendocrinopathy and Enteropathy, X-linked syndrome]) and animal models (e.g., "Scurfy" mouse) is associated with multisystemic autoimmune disease. T(REG) in humans and laboratory animal species are similar in type and regulatory function. A molecular marker of and the cell lineage specification factor for T(REG) is FOXP3, a forkhead box transcription factor. CD4(+) T(REG) are either natural (nT(REG)), which are thymus-derived CD4(+)CD25(+)FOXP3(+) T-cells, or inducible (i.e., Tr1 cells that secrete IL-10, Th3 cells that secrete TGF-β and IL-10, and Foxp3(+) Treg). The proinflammatory Th17 subset has been a major focus of research. T(H)17 CD4(+) effector T-cells secrete IL-17, IL-21, and IL-22 in autoimmune and inflammatory disease, and are dynamically balanced with T(REG) cell development. Other lymphocyte subsets with regulatory function include: inducible CD8(+) T(REG), CD3(+)CD4(-)CD8(-) T(REG) (double-negative), CD4(+)Vα14(+) (NKT(REG)), and γδ T-cells. T(REG) have four regulatory modes of action: secretion of inhibitory cytokines (e.g., IL-10 and TGF-β), granzyme-perforin-induced apoptosis of effector lymphocytes, depriving effector T-cells of cytokines leading to apoptosis, or inhibition of dendritic cell function. The role of T(REG) in mucosal sites, inflammation/infection, pregnancy, and cancer as well as a review of T(REG) as a modulatory target in drug development will be covered.

Immunomodulatory role of Ocimum gratissimum and ascorbic acid against nicotine-induced murine peritoneal macrophages in vitro

The aim of this present study was to evaluate the immune functions and immune responses in nicotine-induced (10 mM) macrophages and concurrently establish the immunomodulatory role of aqueous extract of Ocimum gratissimum (Ae-Og) and ascorbic acid. In this study, nitrite generations and some phenotype functions by macrophages were studied. Beside that, release of Th1 cytokines (TNF-α, IL-12) and Th2 cytokines (IL-10, TGF-β) was measured by ELISA, and the expression of these cytokines at mRNA level was analyzed by real-time PCR. Ae-Og, at a dose of 10 μg/mL, significantly reduced the nicotine-induced NO generation and iNOSII expression. Similar kinds of response were observed with supplementation of ascorbic acid (0.01 mM). The administration of Ae-Og and ascorbic acid increased the decreased adherence, chemotaxis, phagocytosis, and intracellular killing of bacteria in nicotine-treated macrophages. Ae-Og and ascorbic acid were found to protect the murine peritoneal macrophages through downregulation of Th1 cytokines in nicotine-treated macrophages with concurrent activation of Th2 responses. These findings strongly enhanced our understanding of the molecular mechanism leading to nicotine-induced suppression of immune functions and provide additional rationale for application of anti-inflammatory therapeutic approaches by O. gratissimum and ascorbic acid for different inflammatory disease prevention and treatment during nicotine toxicity.

FOXP3+ regulatory T cells: from suppression of rejection to induction of renal allograft tolerance

Naturally occurring and induced regulatory T cells (Tregs) can become hyporesponsive and anergic to antigen stimulation in autoimmune diseases and allograft rejection. The mechanisms of suppression of effector T cells by Tregs remain unclear, but there are in vitro and in vivo evidences showing that these cells are able to suppress antigen-specific responses via direct cell-to-cell contact, secrete anti-inflammatory cytokines such as TGF-β and IL-10, and inhibit the generation of memory T cells, among others. The transcription factor FOXP3 is a specific marker of Tregs and its deficiency is associated with autoimmune diseases and inflammation. During acute rejection of kidney allografts, an augmented FOXP3 gene expression as well as increased CD4(+)CD25(+)FOXP3(+) and other cell populations are observed in graft biopsies. However, it is not clear whether Tregs migrate into the graft and are retained there to suppress the inflammatory process, or whether they are directly associated with more complex mechanisms to induce immune tolerance. FOXP3(+) Tregs may direct the immune response toward a graft acceptance program, potentially affecting the long-term survival of transplanted organs and tissues. Immunosuppressive drugs modulate the number and function of circulating Tregs and FOXP3 expression. Experimental and clinical studies have shown that mTOR inhibitors have positive and calcineurin inhibitors negative effects on Tregs, but it is difficult to set apart the effect of multiple other factors known to be associated with short- and long-term renal graft outcomes. This review aimed to describe the functions of Tregs and its transcription factor FOXP3 in suppression of immune response during rejection and in induction of kidney graft tolerance, as well as to review the individual effects of immunosuppressive drugs on Tregs.

CNI induced Th17/Treg imbalance and susceptibility to renal dysfunction in renal transplantation

Calcineurin inhibitors (CNI) prevent graft rejection by blocking interleukin-2 (IL-2), which was required for development and function of Foxp3(+)CD4(+)CD25(+) regulatory T cells (Treg). Recently, IL-2 was reported to play a part in the inhibition of Th17 cells. The renal transplantation recipient who used CNI regularly might have Th17/Treg imbalance with increased Th17 cells and decreased Treg cells, which would cause renal dysfunction even rejection. To assess the effect of CNI on Th17 cells and Treg cells, we included 123 renal transplantation recipients (101 in a stable stage and 22 with renal dysfunction) and 27 healthy volunteers. Among all the recipients, 103 recipients used CNI and 20 recipients used sirolimus without CNI. The recipients who used CNI were further classified into four groups according to the blood levels of CNI: Of all these subjects, Th17 and Treg frequencies in the peripheral blood were analyzed by flow cytometry (FCM). Serums IL-17, IL-23, IL-6, IFN-r, and TGF-β were analyzed by ELISA. The results demonstrated that the transplantation recipient treated by CNI revealed an obvious increase in peripheral Th17 frequencies and a significant decrease in Treg frequencies when compared with the sirolimus group and healthy people (P<0.05). Even more, the transplantation recipient with renal dysfunction had the highest level of Th17 cells (P<0.05) while the lowest Treg cells compared with stable recipient and healthy control, with increased serums IL-6 and IL-17. Our results indicated that CNI was associated with Th17/Treg imbalance in peripheral blood, which supported the followed generation of renal dysfunction after transplantation.

Association of functional GITR gene polymorphisms related to expression of glucocorticoid-induced tumour necrosis factor-receptor (GITR) molecules with prognosis of autoimmune thyroid disease

The glucocorticoid-induced tumour necrosis factor (TNF)-receptor (GITR) affects the functions of regulatory T (T(reg)) and effector T (T(eff)) cells, but the significance of this phenomenon is still unclear. To examine the association of single nucleotide polymorphisms (SNPs) in the GITR gene with the expression of GITR molecules on T cells and with the pathological conditions in patients with autoimmune thyroid disease (AITD), we examined the frequencies of four candidate SNPs in AITD patients and healthy volunteers by restriction enzyme analysis and direct sequence analyses. We also analysed the GITR expression on peripheral T(reg) and T(eff) cells in AITD patients by three-colour flow cytometry. The CC genotype in the rs3753348 C/G SNP was significantly more frequent in patients with mild Hashimoto's disease (HD) than in those with severe HD [P = 0·0117, odds ratio (OR) = 3·13]. The AA genotype in the rs2298213 A/G SNP was significantly more frequent in patients with mild HD than in patients with severe HD (P = 0·010, OR = 4·43). All patients and healthy individuals had the GG genotype in rs60038293 A/G and rs11466696 A/G SNPs. The proportions of GITR(+) cells in T(reg) and T(eff) cells were significantly higher in AITD patients with the CC genotype of the rs3753348 SNP than in those with the GG genotype (P = 0·004 and P = 0·011, respectively). In conclusion, the rs3753348 C/G SNP in the GITR is associated with HD prognosis and expression on T(reg) and T(eff) cells.

Requirements for prolongation of allograft survival with regulatory T cell infusion in lymphosufficient hosts

BACKGROUND

For the clinical applicability of regulatory T cells (Tregs) in transplantation, it is critical to determine if donor antigen specificity is required for their immunosuppressive function. We developed an allospecific CD4(+) T cell receptor transgenic (TCR-tg) mouse as a source for large numbers of Tregs with defined allospecificity and tested whether they are more effective than polyclonal Tregs at suppressing allograft rejection.

MATERIALS AND METHODS

CD4(+)CD25(+)CD62L(hi) T cells were sorted from the spleen and peripheral lymph nodes of wild-type (WT-Tregs) and TCR-tg (Allo-Tregs) mice, and expanded using IL-2 and anti-CD3/anti-CD28 conjugated magnetic beads. Tregs were tested for their ability to suppress the proliferation and cytokine production of alloreactive CD4(+)CD25(-) T cells in mixed leukocyte assays. Syngeneic WT hosts were adoptively transferred 5 × 10(6) Tregs and transplanted with allogeneic hearts.

RESULTS

Using anti-CD3/anti-CD28 conjugated beads, Tregs were expanded in vitro 100-fold and maintained their suppressor phenotype and function. Allo-Tregs were 6-8 times more potent on a cell-for-cell basis than WT-Tregs in suppressing allospecific proliferation in vitro. Allo-Tregs were unable to suppress in the absence of allo-antigen. Adoptive transfer of expanded Allo-Tregs into WT recipients prolonged the graft survival in a F1 heart transplant model compared with WT-Treg or no treatment [20.0 ± 4.4 d (n = 6) versus 10.4 ± 1.2 (n = 8) and 9.7 ± 1.6 d (n = 6)].

CONCLUSIONS

Unlike polyclonal Tregs, allospecific Tregs are able to prolong allograft survival. However, large numbers of Allo-Tregs were unable to induce tolerance, suggesting that Treg therapy in immunocompetent recipients will require conditioning and/or additional immunomodulation for the induction of tolerance.

Clinical significance of regulatory T-cell-related gene expression in peripheral blood after renal transplantation

BACKGROUND

Regulatory T cells (Tregs) have been suggested to be deeply associated with immune tolerance and long-term graft survival in transplantation. Some recipients with stable graft function (ST) could possibly minimize immunosuppression during the maintenance period. However, effective assays for assessing the suitability of patients have yet to be established. The purpose of this study was to elucidate the clinical relevance of Treg-related gene expression such as forkhead box P3 (Foxp3) in peripheral blood after renal transplantation.

METHODS

Several key molecules related to the function of immune cells such as Treg, including Foxp3, transforming growth factor-β, cytotoxic T-lymphocyte antigen-4, chemokine receptor 7, toll-like receptor 4, granzyme B, T-bet, GATA3, RORC, α1,2-mannosidase, and proteasome subunit β 10 were examined in the peripheral blood of 272 renal transplant recipients by quantitative real-time reverse-transcriptase polymerase chain reaction. The expression levels were compared between recipients with chronic rejection and ST.

RESULTS

Foxp3 messenger RNA (mRNA) levels were reduced immediately after transplantation and gradually recovered. Pretransplantation levels were closely correlated with 1 year posttransplantation levels. Recipients with chronic rejection had significantly lower levels of Foxp3, chemokine receptor 7, and granzyme B mRNA, and higher levels of toll-like receptor 4 and proteasome subunit β 10 mRNA compared with those with ST, although Foxp3 was the most relevant marker.

CONCLUSION

There is a possibility that monitoring mRNA expression levels of Treg-related molecules in peripheral blood might offer useful information on patient selection and early detection of rejection when immunosuppression minimization strategy is implemented in renal transplantation.

Toward managing chronic rejection after lung transplant: the fate and effects of inhaled cyclosporine in a complex environment

The fate and effects of inhaled cyclosporine A (CsA) are considered after deposition on the lung surface. Special emphasis is given to a post-lung transplant environment and to the potential effects of the drug on the various cell types it is expected to encounter. The known stability, metabolism, pharmacokinetics and pharmacodynamics of the drug have been reviewed and discussed in the context of the lung microenvironment. Arguments support the contention that the immuno-inhibitory and anti-inflammatory effects of CsA are not restricted to T-cells. It is likely that pharmacologically effective concentrations of CsA can be sustained in the lungs but due to the complexity of uptake and action, the elucidation of effective posology must ultimately rely on clinical evidence.

TGF-beta, IL-6, IL-17 and CTGF direct multiple pathologies of chronic cardiac allograft rejection

Cardiac transplantation is an effective treatment for heart failure refractive to therapy. Although immunosuppressive therapeutics have increased first year survival rates, chronic rejection remains a significant barrier to long-term graft survival. Chronic rejection manifests as patchy interstitial fibrosis, vascular occlusion and progressive loss of graft function. Recent evidence from experimental and patient studies suggests that the development of cardiomyocyte hypertrophy is another hallmark of chronic cardiac allograft rejection. This pathologic hypertrophy is tightly linked to the immune cytokine IL-6, which promotes facets of chronic rejection in concert with TGF-beta and IL-17. These factors potentiate downstream mediators, such as CTGF, which promote the fibrosis associated with the disease. In this article, we summarize contemporary findings that have revealed several elements involved in the induction and progression of chronic rejection of cardiac allografts. Further efforts to elucidate the interplay between these factors may direct the development of targeted therapies for this disease.

Immunotherapy following hematopoietic stem cell transplantation: potential for synergistic effects

Hematopoietic stem cell transplantation (HSCT) is a particularly important treatment for hematologic malignancies. Unfortunately, following allogeneic HSCT, graft-versus-host disease, immunosuppression and susceptibility to opportunistic infections remain among the most substantial problems restricting the efficacy and use of this procedure, particularly for cancer. Adoptive immunotherapy and/or manipulation of the graft offer ways to attack residual cancer as well as other transplant-related complications. Recent exciting discoveries have demonstrated that HSCT could be expanded to solid tissue cancers with profound effects on the effectiveness of adoptive immunotherapy. This review will provide a background regarding HSCT, discuss the complications that make it such a complex treatment procedure following up with current immunotherapeutic strategies and discuss emerging approaches in applying immunotherapy in HSCT for cancer.

Do cannabinoids have a therapeutic role in transplantation?

Cannabinoids have emerged as powerful drug candidates for the treatment of inflammatory and autoimmune diseases due to their immunosuppressive properties. Significant clinical and experimental data on the use of cannabinoids as anti-inflammatory agents exist in many autoimmune disease settings, but virtually no studies have been undertaken on their potential role in transplant rejection. Here we suggest a theoretical role for the use of cannabinoids in preventing allograft rejection. The psychotropic properties of CB1 agonists limit their clinical use, but CB2 agonists may offer a new avenue to selectively target immune cells involved in allograft rejection. Moreover, development of mixed CB1/CB2 agonists that cannot cross the blood-brain barrier may help prevent their undesired psychotropic properties. In addition, manipulation of endocannabinoids in vivo by activating their biosynthesis and inhibiting cellular uptake and metabolism may offer another pathway to regulate immune response during allograft rejection.

Connective tissue growth factor promotes fibrosis downstream of TGFbeta and IL-6 in chronic cardiac allograft rejection

Cardiac transplantation is an effective treatment for multiple types of heart failure refractive to therapy. Although immunosuppressive therapeutics have increased survival rates within the first year posttransplant, chronic rejection (CR) remains a significant barrier to long-term graft survival. Indicators of CR include patchy interstitial fibrosis, vascular occlusion and progressive loss of graft function. Multiple factors have been implicated in the onset and progression of CR, including TGFbeta, IL-6 and connective tissue growth factor (CTGF). While associated with CR, the role of CTGF in CR and the factors necessary for CTGF induction in vivo are not understood. To this end, we utilized forced expression and neutralizing antibody approaches. Transduction of allografts with CTGF significantly increased fibrotic tissue development, though not to levels observed with TGFbeta transduction. Further, intragraft CTGF expression was inhibited by IL-6 neutralization whereas TGFbeta expression remained unchanged, indicating that IL-6 effects may potentiate TGFbeta-mediated induction of CTGF. Finally, neutralizing CTGF significantly reduced graft fibrosis without reducing TGFbeta and IL-6 expression levels. These findings indicate that CTGF functions as a downstream mediator of fibrosis in CR, and that CTGF neutralization may ameliorate fibrosis and hypertrophy associated with CR.

Challenges in clinical design of immunotherapy trials for malignant glioma

Glioblastoma multiforme (GBM) is the most common and lethal primary malignant brain tumor. The traditional treatments for GBM, including surgery, radiation, and chemotherapy, only modestly improve patient survival. Therefore, immunotherapy has emerged as a novel therapeutic modality. Immunotherapeutic strategies exploit the immune system's ability to recognize and mount a specific response against tumor cells, but not normal cells. Current immunotherapeutic approaches for glioma can be divided into 3 categories: immune priming (active immunotherapy), immunomodulation (passive immunotherapy), and adoptive immunotherapy. Immune priming sensitizes the patient's immune cells to tumor antigens using various vaccination protocols. In the case of immunomodulation, strategies are aimed at reducing suppressive cytokines in the tumor microenvironment or using immune molecules to specifically target tumor cells. Adoptive immunotherapy involves harvesting the patient's immune cells, followed by ex vivo activation and expansion before reinfusion. This article provides an overview of the interactions between the central nervous system and the immune system, and discusses the challenges facing current immunotherapeutic strategies.

TGFbeta neutralization within cardiac allografts by decorin gene transfer attenuates chronic rejection

Chronic allograft rejection (CR) is the leading cause of late graft failure following organ transplantation. CR is a progressive disease, characterized by deteriorating graft function, interstitial fibrosis, cardiac hypertrophy, and occlusive neointima development. TGFbeta, known for its immunosuppressive qualities, plays a beneficial role in the transplant setting by maintaining alloreactive T cells in a hyporesponsive state, but has also been implicated in promoting graft fibrosis and CR. In the mouse vascularized cardiac allograft model, transient depletion of CD4(+) cells promotes graft survival but leads to CR, which is associated with intragraft TGFbeta expression. Decorin, an extracellular matrix protein, inhibits both TGFbeta bioactivity and gene expression. In this study, gene transfer of decorin into cardiac allografts was used to assess the impact of intragraft TGFbeta neutralization on CR, systemic donor-reactive T cell responses, and allograft acceptance. Decorin gene transfer and neutralization of TGFbeta in cardiac allografts significantly attenuated interstitial fibrosis, cardiac hypertrophy, and improved graft function, but did not result in systemic donor-reactive T cell responses. Thus, donor-reactive T and B cells remained in a hyporesponsive state. These findings indicate that neutralizing intragraft TGFbeta inhibits the cytokine's fibrotic activities, but does not reverse its beneficial systemic immunosuppressive qualities.

Role of T cell TGFbeta signaling and IL-17 in allograft acceptance and fibrosis associated with chronic rejection

Chronic allograft rejection (CR) is the main barrier to long-term transplant survival. CR is a progressive disease defined by interstitial fibrosis, vascular neointimal development, and graft dysfunction. The underlying mechanisms responsible for CR remain poorly defined. TGFbeta has been implicated in promoting fibrotic diseases including CR, but is beneficial in the transplant setting due to its immunosuppressive activity. To assess the requirement for T cell TGFbeta signaling in allograft acceptance and the progression of CR, we used mice with abrogated T cell TGFbeta signaling as allograft recipients. We compared responses from recipients that were transiently depleted of CD4(+) cells (that develop CR and express intragraft TGFbeta) with responses from mice that received anti-CD40L mAb therapy (that do not develop CR and do not express intragraft TGFbeta). Allograft acceptance and suppression of graft-reactive T and B cells were independent of T cell TGFbeta signaling in mice treated with anti-CD40L mAb. In recipients transiently depleted of CD4(+) T cells, T cell TGFbeta signaling was required for the development of fibrosis associated with CR, long-term graft acceptance, and suppression of graft-reactive T and B cell responses. Furthermore, IL-17 was identified as a critical element in TGFbeta-driven allograft fibrosis. Thus, IL-17 may provide a therapeutic target for preventing graft fibrosis, a measure of CR, while sparing the immunosuppressive activity of TGFbeta.

Expression of a CD200 transgene is necessary for induction but not maintenance of tolerance to cardiac and skin allografts

CD200, a type 2 transmembrane molecule of the Ig supergene family, can induce immunosuppression in a number of biological systems, as well as promote increased graft acceptance, following binding to its receptors (CD200Rs). Skin and cardiac allograft acceptance are readily induced in transgenic mice overexpressing CD200 under control of a doxycycline-inducible promoter, both of which are associated with increased intragraft expression of mRNAs for a number of genes associated with altered T cell subset differentiation, including GATA-3, type 2 cytokines (IL-4, IL-13), GITR, and Foxp3. Interestingly, some 12-15 days after grafting, induction of transgenic CD200 expression can be stopped (by doxycycline withdrawal), without obvious significant effect on graft survival. However, neutralization of all CD200 expression (including endogenous CD200 expression) by anti-CD200 mAb caused graft loss, as did introduction of an acute inflammatory stimulus (LPS, 10 microg/mouse, delivered by i.p. injection). We conclude that even with apparently stably accepted tissue allografts, disruption of the immunoregulatory balance by an intense inflammatory stimulus can cause graft loss.

Expression of regulatory T-cell-related molecule genes and clinical outcome in kidney transplant recipients

BACKGROUND

Naturally occurring regulatory T cells have been associated with long-term allograft survival. We investigated whether gene transcripts of Treg-related molecules are upregulated or downregulated in kidney transplant recipients with different clinical outcomes and may serve as markers of operative tolerance.

METHODS

Expression levels of transcription factor (forkhead box P3 [FOXP3], t-bet, and GATA3), regulatory molecule (cytotoxic T-lymphocyte antigen-4, glucocorticoid-induced tumor necrosis factor receptor-related protein, tribbles protein-1, and transforming growth factor-beta), and chemokine receptor (CCR7 and CXCR4) genes were measured in kidney graft recipients with long-term (> or = 9 years) stable renal function (LTS) or chronic rejection (ChrRx). Patients on dialysis and healthy individuals served as controls.

RESULTS

The level of FOXP3 transcripts was lower in ChrRx patients than in LTS patients (P<0.01). The highest transforming growth factor-beta transcripts were observed in ChrRx and the highest CCR7 and CXCR4 transcripts were observed in LTS patients. In LTS patients, FOXP3 gene expression was associated with CXCR4 gene expression (P=0.015). FOXP3 and CCR7 transcript levels were higher in LTS patients without calcineurin inhibitor therapy than in LTS patients with calcineurin inhibitors.

CONCLUSION

Our results suggest that high expression of FOXP3 and chemokine receptor genes in LTS patients are possible indicators of a regulatory process that contributes to long-term allograft acceptance. Markers that were increased in LTS patients were found to be decreased in ChrRx patients, suggesting that rejection may partly be the result of a lack of this regulatory process. FOXP3 and CCR7 and CXCR4 transcripts might be used as markers to distinguish patients who developed long-term allograft acceptance from patients who are prone to ChrRx.

Regulatory, effector, and cytotoxic T cell profiles in long-term kidney transplant patients

Animal studies have suggested a potential role for regulatory T cells (Tregs) in allograft tolerance, but these FOXP3+ cells seem to be an inherent component of acute rejection (AR) in human recipients of renal transplants. The balance between regulatory cells and effector/cytotoxic cells may determine graft outcome; this balance has not been described for chronic allograft injury. We investigated the expression of key regulatory, effector, and cytotoxic transcripts (i.e., FOXP3, T-bet, and granzyme B, respectively) in the grafts and peripheral blood of long-term-surviving renal transplant patients. We found that, whereas neither intragraft nor peripheral blood FOXP3 or T-bet mRNA could distinguish between rejection and nonrejection status, granzyme B (GrzB) mRNA could: It was significantly increased in the graft and significantly decreased in the peripheral blood of patients with chronic antibody-mediated rejection (CAMR). Quantifying peripheral blood GrzB mRNA demonstrated potential to aid in the noninvasive diagnosis of CAMR. In summary, these data affirm GrzB as a marker not only for AR but also for CAMR. In addition, we identified several previously unreported clinical or demographic factors influencing regulatory/effector/cytotoxic profiles in the peripheral blood, highlighting the necessity to consider confounding variables when considering the use of potential biomarkers, such as FOXP3, for diagnosis or prognosis in kidney transplantation.

Regulatory T cells after organ transplantation: where does their action take place?

Regulatory T cells are considered to be pivotal for the induction of tolerance to donor antigens. In the past decades, several regulatory T-cell subsets have been identified, such as CD4(+)CD25(+) regulatory T cells and the CD8(+)CD28(-) suppressor T cells. Although many studies have investigated the role of these regulators in transplant tolerance, relatively little attention has focused on the exact place where these cells suppress immune responses directed to donor antigens. The localization of regulatory T cells may influence their effect on allogeneic immune responses. More insight into the localization and migration of regulatory T cells in transplant recipients is therefore important, especially when these cells are to be used for monitoring purposes and for cellular immune therapy. In the present review we summarize current knowledge about the presence of functional donor-directed regulatory T cells in the secondary lymphoid organs, peripheral blood, and the transplanted organ itself. In addition, we discuss the importance of the appropriate localization for the control of anti-donor immune reactivity.