Peripherally circulating CD4⁺ FOXP3⁺ CXCR3⁺ T regulatory cells correlate with renal allograft function

Different Patterns of Foxp3 Gene Expression in Pre-and Post-Transplantation Kidney Biopsies and the Effect of Use Mammalian Target of Rapamycin Inhibitors

BACKGROUND

Trafficking of regulatory T cells (Tregs) modulates the inflammatory response after kidney transplantation (KTx). There is scarce information on whether circulating and intragraft Tregs are similarly affected by immunosuppressive drugs and the type of deceased kidney donor.

METHODS

FOXP3 gene expression was measured in the pretransplant kidney biopsies (PIBx) from donors who met extended (ECD) and standard (SCD) criteria donors. In the third month after KTx, the patients were divided according to tacrolimus (Tac) or everolimus (Eve) and the type of kidney they had received. FOXP3 gene expression in the peripheral blood (PB) and kidney biopsies (Bx) was analyzed using real-time polymerase chain reaction.

RESULTS

FOXP3 gene expression in the PIBx was higher in ECD kidneys. FOXP3 gene expression in the PB and Bx was greater in Eve- than in Tac-treated patients. However, SCD recipients treated with Eve (SCD/Eve) had higher FOXP3 expression than ECD/Eve.

CONCLUSION

Pretransplant kidney biopsies from ECD kidneys had higher FOXP3 gene expression than SCD, and the use of Eve may affect the expression of the FOXP3 gene only in SCD kidneys.

Human CD4+CD25+CD127lowFOXP3+ regulatory T lymphocytes and CD4+CD25-FOXP3- conventional T lymphocytes: a differential transcriptome profile

CD4+CD25+ FOXP3+ regulatory T cells (Tregs) represent a subpopulation of CD4+ T cells central for the suppression of physiological and pathological immune reactions. Although distinct cell surface antigens are expressed in regulatory T cells, those components are also present on the surface of activated CD4+CD25- FOXP3-T cells, thus making the discrimination between Tregs and conventional CD4+ T difficult and isolation of Tregs complex. Yet, the molecular components driving Tregs' function are still not fully characterized. Aiming at unraveling molecular components specifically marking Tregs, and upon using quantitative real-time PCR (qRT-PCR) followed by bioinformatics analysis, we identified, in this study, differential transcriptional profiles, in peripheral blood CD4 + CD25 + CD127low FOXP3+ Tregs versus CD4 + CD25-FOXP3- conventional T cells, for set of genes with distinct immunological roles. In conclusion, this study identifies some novel genes that appeared to be differentially transcribed in CD4+ Tregs versus conventional T cells. The identified genes could serve as novel molecular targets relevant to Tregs' function and isolation.

CD4+CD25+ T regulatory cells in renal transplantation

The immune response to an allograft activates lymphocytes with the capacity to cause rejection. Activation of CD4+CD25+Foxp3+T regulatory cells (Treg) can down-regulate allograft rejection and can induce immune tolerance to the allograft. Treg represent <10% of peripheral CD4+T cells and do not markedly increase in tolerant hosts. CD4+CD25+Foxp3+T cells include both resting and activated Treg that can be distinguished by several markers, many of which are also expressed by effector T cells. More detailed characterization of Treg to identify increased activated antigen-specific Treg may allow reduction of non-specific immunosuppression. Natural thymus derived resting Treg (tTreg) are CD4+CD25+Foxp3+T cells and only partially inhibit alloantigen presenting cell activation of effector cells. Cytokines produced by activated effector cells activate these tTreg to more potent alloantigen-activated Treg that may promote a state of operational tolerance. Activated Treg can be distinguished by several molecules they are induced to express, or whose expression they have suppressed. These include CD45RA/RO, cytokine receptors, chemokine receptors that alter pathways of migration and transcription factors, cytokines and suppression mediating molecules. As the total Treg population does not increase in operational tolerance, it is the activated Treg which may be the most informative to monitor. Here we review the methods used to monitor peripheral Treg, the effect of immunosuppressive regimens on Treg, and correlations with clinical outcomes such as graft survival and rejection. Experimental therapies involving ex vivo Treg expansion and administration in renal transplantation are not reviewed.

Temporal and sex-dependent gene expression patterns in a renal ischemia-reperfusion injury and recovery pig model

Men are more prone to acute kidney injury (AKI) and chronic kidney disease (CKD), progressing to end-stage renal disease (ESRD) than women. Severity and capacity to regenerate after AKI are important determinants of CKD progression, and of patient morbidity and mortality in the hospital setting. To determine sex differences during injury and recovery we have generated a female and male renal ischemia/reperfusion injury (IRI) pig model, which represents a major cause of AKI. Although no differences were found in blood urea nitrogen (BUN) and serum creatinine (SCr) levels between both sexes, females exhibited higher mononuclear infiltrates at basal and recovery, while males showed more tubular damage at injury. Global transcriptomic analyses of kidney biopsies from our IRI pig model revealed a sexual dimorphism in the temporal regulation of genes and pathways relevant for kidney injury and repair, which was also detected in human samples. Enrichment analysis of gene sets revealed five temporal and four sexual patterns governing renal IRI and recovery. Overall, this study constitutes an extensive characterization of the time and sex differences occurring during renal IRI and recovery at gene expression level and offers a template of translational value for further study of sexual dimorphism in kidney diseases.

Different subpopulations of regulatory T cells in human autoimmune disease, transplantation, and tumor immunity

CD4⁺CD25⁺ regulatory T cells (Tregs), a subpopulation of naturally CD4⁺ T cells that characteristically express transcription factor Forkhead box P3 (FOXP3), play a pivotal role in the maintenance of immune homeostasis and the prevention of autoimmunity. With the development of biological technology, the understanding of plasticity and stability of Tregs has been further developed. Recent studies have suggested that human Tregs are functionally and phenotypically diverse. The functions and mechanisms of different phenotypes of Tregs in different disease settings, such as tumor microenvironment, autoimmune diseases, and transplantation, have gradually become hot spots of immunology research that arouse extensive attention. Among the complex functions, CD4⁺CD25⁺FOXP3⁺ Tregs possess a potent immunosuppressive capacity and can produce various cytokines, such as IL‐2, IL‐10, and TGF‐β, to regulate immune homeostasis. They can alleviate the progression of diseases by resisting inflammatory immune responses, whereas promoting the poor prognosis of diseases by helping cells evade immune surveillance or suppressing effector T cells activity. Therefore, methods for targeting Tregs to regulate their functions in the immune microenvironment, such as depleting them to strengthen tumor immunity or expanding them to treat immunological diseases, need to be developed. Here, we discuss that different subpopulations of Tregs are essential for the development of immunotherapeutic strategies involving Tregs in human diseases.

Immune-Related Genes for Predicting Future Kidney Graft Loss: A Study Based on GEO Database

Objective

We aimed to identify feature immune-related genes that correlated with graft rejection and to develop a prognostic model based on immune-related genes in kidney transplantation.

Methods

Gene expression profiles were obtained from the GEO database. The GSE36059 dataset was used as a discovery cohort. Then, differential expression analysis and a machine learning method were performed to select feature immune-related genes. After that, univariate and multivariate Cox regression analyses were used to identify prognosis-related genes. A novel Riskscore model was built based on the results of multivariate regression. The levels of these feature genes were also confirmed in an independent single-cell dataset and other GEO datasets.

Results

15 immune-related genes were expressed differently between non-rejection and rejection kidney allografts. Those differentially expressed immune-related genes (DE-IRGs) were mainly associated with immune-related biological processes and pathways. Subsequently, a 5-immune-gene signature was constructed and showed favorable predictive results in the GSE21374 dataset. Recipients were divided into the high-risk and low-risk groups according to the median value of RiskScore. The GO and KEGG analysis indicated that the differentially expressed genes (DEGs) between high-risk and low-risk groups were mainly involved in inflammatory pathways, chemokine-related pathways, and rejection-related pathways. Immune infiltration analysis demonstrated that RiskScore was potentially related to immune infiltration. Kaplan-Meier survival analysis suggested that recipients in the high-risk group had poor graft survival. AUC values of 1- and 3-year graft survival were 0.804 and 0.793, respectively.

Conclusion

Our data suggest that this immune-related prognostic model had good sensitivity and specificity in predicting the 1- and 3-year kidney graft survival and might act as a useful tool for predicting kidney graft loss.

Human chorionic gonadotropin potentially affects pregnancy outcome in women with recurrent implantation failure by regulating the homing preference of regulatory T cells

PROBLEM

Human chorionic gonadotropin (hCG) and regulatory T cells (Tregs) have been suggested to play important roles during the initial stage of pregnancy. However, the clinical relevance and mechanism of the effects of hCG on Treg functions in women with recurrent implantation failure (RIF) remain to be elucidated.

METHOD OF STUDY

Thirty-four RIF and twenty-three control women were included in the study. Endometrial and peripheral Tregs were analyzed by immunohistochemistry and flow cytometry, respectively. Tregs were generated from naïve CD4⁺ T cells by stimulation with anti-CD3/CD28 in the presence or absence of hCG, and the subsets were analyzed by flow cytometry, Western blotting, and qPCR.

RESULTS

The percentages of endometrial FOXP3⁺ Tregs and peripheral CCR4⁺ FOXP3⁺ Tregs were significantly lower in the women with RIF than in the healthy controls. In addition, the percentages of CCR4⁺ FOXP3⁺ Tregs and TGF-β-expressing FOXP3⁺ Tregs were increased following the stimulation of naïve CD4⁺ T cells with anti-CD3/CD28, and these increases were concomitant with AKT and ERK dephosphorylation.

CONCLUSIONS

The results of this study provide novel evidence supporting a role of hCG in regulating the differentiation of peripheral FOXP3⁺ Tregs. The alterations of circulating Tregs may positively affect the pregnancy outcomes of patients with a history of RIF.

Protective Effect of CXCR3⁺CD4⁺CD25⁺Foxp3⁺ Regulatory T Cells in Renal Ischemia-Reperfusion Injury

Regulatory T cells (Tregs) suppress excessive immune responses and are potential therapeutic targets in autoimmune disease and organ transplantation rejection. However, their role in renal ischemia-reperfusion injury (IRI) is unclear. Levels of Tregs and expression of CXCR3 in Tregs were analyzed to investigate their function in the early phase of renal IRI. Mice were randomly divided into Sham, IRI, and anti-CD25 (PC61) + IRI groups. The PC61 + IRI group was established by i.p. injection of PC61 monoclonal antibody (mAb) to deplete Tregs before renal ischemia. CD4⁺CD25⁺Foxp3⁺ Tregs and CXCR3 on Tregs were analyzed by flow cytometry. Blood urea nitrogen (BUN), serum creatinine (Scr) levels, and tubular necrosis scores, all measures of kidney injury, were greater in the IRI group than in the Sham group. Numbers of Tregs were increased at 72 h after reperfusion in kidney. PC61 mAb preconditioning decreased the numbers of Tregs and aggravated kidney injury. There was no expression of CXCR3 on Tregs in normal kidney, while it expanded at 72 h after reperfusion and inversely correlated with BUN, Scr, and kidney histology score. This indicated that recruitment of Tregs into the kidney was related to the recovery of renal function after IRI and CXCR3 might be involved in the migration of Tregs.

Infiltrating Foxp3(+) regulatory T cells from spontaneously tolerant kidney allografts demonstrate donor-specific tolerance

Foxp3(+) regulatory T cells (Tregs) have an essential role in immune and allograft tolerance. However, in both kidney and liver transplantation in humans, FOXP3(+) Tregs have been associated with clinical rejection. Therefore, the role and function of graft infiltrating Tregs have been of great interest. In the studies outlined, we demonstrated that Foxp3(+) Tregs were expanded in tolerant kidney allografts and in draining lymph nodes in the DBA/2 (H-2(d) ) to C57BL/6 (H-2(b) ) mouse spontaneous kidney allograft tolerance model. Kidney allograft tolerance was abrogated after deletion of Foxp3(+) Tregs in DEpletion of REGulatory T cells (DEREG) mice. Kidney allograft infiltrating Foxp3(+) Tregs (K-Tregs) expressed elevated levels of TGF-β, IL-10, interferon gamma (IFN-γ), the transcriptional repressor B lymphocyte-induced maturation protein-1 (Blimp-1) and chemokine receptor 3 (Cxcr3). These K-Tregs had the capacity to transfer dominant tolerance and demonstrate donor alloantigen-specific tolerance to skin allografts. This study demonstrated the crucial role, potency and specificity of graft infiltrating Foxp3(+) Tregs in the maintenance of spontaneously induced kidney allograft tolerance.

Foxp3+ Helios+ regulatory T cells are expanded in active systemic lupus erythematosus

OBJECTIVES

Recent data debate the suitability of Helios, an Ikaros family member, as a marker for thymic-derived regulatory T cells (Treg). Nevertheless, Foxp3(+) Helios(+) Treg may be of particular relevance in mediating immune tolerance in chronic autoimmunity, such as systemic lupus erythematosus (SLE), as they possess enhanced suppressive function, compared to Foxp3(+) Helios(-) Treg.

METHODS

Multicolour flow cytometry was performed to analyse Foxp3 and Helios expression in peripheral blood CD4 T cells from SLE patients, compared to healthy controls (HC) and systemic sclerosis (SSc) and rheumatoid arthritis (RA) patients. Cytokine production, chemokine receptor expression for CXCR3 and CCR4, basal signal transducer and activator of transcription 5 (STAT5)a phosphorylation levels and T-cell receptor (TCR) Vβ repertoire were analysed by flow cytometry, and the methylation status of the Foxp3 locus (Treg-specific demethylated region, TSDR) by real-time PCR.

RESULTS

Frequencies of Foxp3(+) Helios(+) Treg, unlike Foxp3(+) Helios(-) T cells, were significantly increased in SLE patients and positively correlated with disease activity, whereas they were unaltered in SSc and RA patients. Compared to HC, Foxp3(+) Helios(+) Treg in SLE predominantly displayed a CD45RA(-)/CD31(-)/FoxP3(low) memory phenotype with increased Ki-67 expression, enhanced basal pSTAT5a levels and a restricted TCR repertoire. Nonetheless, similar to HC, Foxp3(+) Helios(+) Treg in SLE lacked effector cytokine production, possessed a highly demethylated TSDR and expressed comparable levels of CXCR3 and CCR4.

CONCLUSIONS

Our data suggest that Helios-expressing Foxp3(+) Treg with functional suppressive capacity and migratory potential into inflamed tissues are expanded in active SLE, presumably through γ-chain signalling cytokines and TCR stimulation, to compensate for autoreactive effector responses.

The need for inducing tolerance in vascularized composite allotransplantation

Successful hand and face transplantation in the last decade has firmly established the field of vascularized composite allotransplantation (VCA). The experience in VCA has thus far been very similar to solid organ transplantation in terms of the morbidity associated with long-term immunosuppression. The unique immunological features of VCA such as split tolerance and resistance to chronic rejection are being investigated. Simultaneously there has been laboratory work studying tolerogenic protocols in animal VCA models. In order to optimize VCA outcomes, translational studies are needed to develop less toxic immunosuppression and possibly achieve donor-specific tolerance. This article reviews the immunology, animal models, mixed chimerism & tolerance induction in VCA and the direction of future research to enable better understanding and wider application of VCA.