CD45RC isoform expression identifies functionally distinct T cell subsets differentially distributed between healthy individuals and AAV patients

Renal graft function in transplanted patients correlates with CD45RC T cell phenotypic signature

Biomarkers that could predict the evolution of the graft in transplanted patients and that could allow to adapt the care of the patients would be an invaluable tool. Additionally, certain biomarkers can be target of treatments and help to stratify patients. Potential effective biomarkers have been identified but still need to be confirmed. CD45RC, one of the splicing variants of the CD45 molecule, a tyrosine phosphatase that is critical in negatively or positively regulating the TCR and the BCR signaling, is one marker already described. The frequency of CD8+ T cells expressing high levels of CD45RC before transplantation is increased in patients with an increased risk of acute rejection. However, single biomarkers have limited predictive reliability and the correlation of the expression levels of CD45RC with other cell markers was not reported. In this study, we performed a fluorescent-based high dimensional immunophenotyping of T cells on a cohort of 69 kidney transplant patients either with stable graft function or having experienced acute transplant rejection during the first year after transplantation or at the time of rejection. We identified combinations of markers and cell subsets associated with activation/inflammation or Tregs/tolerance (HLA-DR, PD-1, IFNγ, CD28) as significant biomarkers associated to transplant outcome, and showed the importance of cell segregation based on the CD45RC marker to identify the signature of a stable graft function. Our study highlights potential reliable biomarkers in transplantation to predict and/or monitor easily graft-directed immune responses and adapt immunosuppression treatments to mitigate adverse effects.

Neuroinflammation: Extinguishing a blaze of T cells

Inflammation is a biological process that dynamically alters the surrounding microenvironment, including participating immune cells. As a well-protected organ surrounded by specialized barriers and with immune privilege properties, the central nervous system (CNS) tightly regulates immune responses. Yet in neuroinflammatory conditions, pathogenic immunity can disrupt CNS structure and function. T cells in particular play a key role in promoting and restricting neuroinflammatory responses, while the inflamed CNS microenvironment can influence and reshape T cell function and identity. Still, the contraction of aberrant T cell responses within the CNS is not well understood. Using autoimmunity as a model, here we address the contribution of CD4 T helper (Th) cell subsets in promoting neuropathology and disease. To address the mechanisms antagonizing neuroinflammation, we focus on the control of the immune response by regulatory T cells (Tregs) and describe the counteracting processes that preserve their identity under inflammatory challenges. Finally, given the influence of the local microenvironment on immune regulation, we address how CNS-intrinsic signals reshape T cell function to mitigate abnormal immune T cell responses.

Anti-CD45RC antibody immunotherapy prevents and treats experimental Autoimmune PolyEndocrinopathy Candidiasis Ectodermal Dystrophy syndrome

Targeted monoclonal antibody (mAb) therapies show great promise for the treatment of transplant rejection and autoimmune diseases by inducing more specific immunomodulatory effects than broadly immunosuppressive drugs routinely used. We recently described the therapeutic advantage of targeting CD45RC, expressed at high levels by conventional T cells (Tconv, CD45RChigh), their precursors and terminally differentiated T (TEMRA) cells, but not by regulatory T cells (Tregs, CD45RClow/-). We demonstrated efficacy of anti-CD45RC mAb treatment in transplantation but its potential has not been examined in autoimmune diseases. APECED is a rare genetic syndrome caused by loss-of-function mutations of the key central tolerance mediator, autoimmune regulator (AIRE) leading to abnormal auto-reactive T cell responses and autoantibodies production. Herein, we showed that, in a rat model of APECED syndrome, anti-CD45RC mAb was effective both as prevention and treatment of autoimmune manifestations and inhibited autoantibody development. Anti-CD45RC mAb intervention depleted CD45RChigh T cells, inhibited CD45RChigh B cells, and restored the Treg/Tconv ratio and the altered Tregs transcriptomic profile. In APECED patients, CD45RC was significantly increased in peripheral blood T cells and lesioned organs from APECED patients were infiltrated by CD45RChigh cells. Our observations highlight the potential role for CD45RChigh cells in the pathogenesis of experimental and human APECED syndrome and the potential of anti-CD45RC antibody treatment.

Transient antibody targeting of CD45RC inhibits the development of graft-versus-host disease

Allogeneic bone marrow transplantation (BMT) is a widely spread treatment of many hematological diseases, but its most important side effect is graft-versus-host disease (GVHD). Despite the development of new therapies, acute GVHD (aGVHD) occurs in 30% to 50% of allogeneic BMT and is characterized by the generation of effector T (Teff) cells with production of inflammatory cytokines. We previously demonstrated that a short anti-CD45RC monoclonal antibody (mAb) treatment in a heart allograft rat model transiently decreased CD45RChigh Teff cells and increased regulatory T cell (Treg) number and function allowing long-term donor-specific tolerance. Here, we demonstrated in rat and mouse allogeneic GVHD, as well as in xenogeneic GVHD mediated by human T cells in NSG mice, that both ex vivo depletion of CD45RChigh T cells and in vivo treatment with short-course anti-CD45RC mAbs inhibited aGVHD. In the rat model, we demonstrated that long surviving animals treated with anti-CD45RC mAbs were fully engrafted with donor cells and developed a donor-specific tolerance. Finally, we validated the rejection of a human tumor in NSG mice infused with human cells and treated with anti-CD45RC mAbs. The anti-human CD45RC mAbs showed a favorable safety profile because it did not abolish human memory antiviral immune responses, nor trigger cytokine release in in vitro assays. Altogether, our results show the potential of a prophylactic treatment with anti-human CD45RC mAbs in combination with rapamycin as a new therapy to treat aGVHD without abolishing the antitumor effect.

CD8+ Tregs revisited: A heterogeneous population with different phenotypes and properties

Regulatory T cells (Tregs) play a key role in the peripheral self-tolerance and preventing autoimmunity. While classical CD4⁺ Foxp3⁺ Tregs are well established, their CD8⁺ counterparts are still controversial in many aspects including their phenotypic identity and their mechanisms of suppression. Because of these controversies and because of only a limited number of studies documenting the immunoregulatory function of CD8⁺ Tregs in vivo, the concept of CD8⁺ Tregs is still not unanimously accepted. We propose that any T-cell subset considered as true regulatory must be distinguishable from other cell types and must suppress in vivo immune responses via a known mechanism. In this article, we revisit the concept of CD8⁺ Tregs by focusing on the characterization of individual CD8⁺ T-cell subsets with proposed regulatory capacity separately. Therefore, we review the phenotype and function of CD8⁺ FOXP3⁺ T cells, CD8⁺ CD122⁺ T cells, CD8⁺ CD28^low/- T cells, CD8⁺ CD45RC^low T cells, T cells expressing CD8αα homodimer and Qa-1-restricted CD8⁺ T cells to show whether there is sufficient evidence to establish these subsets as bona fide Tregs. Based on the intrinsic ability of CD8⁺ Treg subsets to promote immune tolerance in animal models, we elaborate on their potential use in clinics.

Mass spectrometry-based proteomic exploration of the small urinary extracellular vesicles in ANCA-associated vasculitis in comparison with total urine

ANCA-associated vasculitis (AAV) is a rare, but potentially severe autoimmune disease, even nowadays displaying increased mortality and morbidity. Finding early biomarkers of activity and prognosis is thus very important. Small extracellular vesicles (EVs) isolated from urine can be considered as a non-invasive source of biomarkers. We evaluated several protocols for urinary EV isolation. To eliminate contaminating non-vesicular proteins due to AAV associated proteinuria we used proteinase K treatment. We investigated the differences in proteomes of small EVs of patients with AAV compared to healthy controls by label-free LC-MS/MS. In parallel, we performed an analogous proteomic analysis of urine samples from identical patients. The study results showed significant differences and similarities in both EV and urine proteome, the latter one being highly affected by proteinuria. Using bioinformatics tools we explored differentially changed proteins and their related pathways with a focus on the pathophysiology of AAV. Our findings indicate significant regulation of Golgi enzymes, such as MAN1A1, which can be involved in T cell activation by N-glycans glycosylation and may thus play a key role in pathogenesis and diagnosis of AAV. SIGNIFICANCE: The present study explores for the first time the changes in proteomes of small extracellular vesicles and urine of patients with renal ANCA-associated vasculitis compared to healthy controls by label-free LC-MS/MS. Isolation of vesicles from proteinuric urine samples has been modified to minimize contamination by plasma proteins and to reduce co-isolation of extraluminal proteins. Differentially changed proteins and their related pathways with a role in the pathophysiology of AAV were described and discussed. The results could be helpful for the research of potential biomarkers in renal vasculitis associated with ANCA.

CD8+ T cells: The past and future of immune regulation

Regulation of the adaptive immune response is critical for health. Regulatory activity can be found in multiple components of the immune system, however, the focus on particular components of the immune regulatory network has left many aspects of this critical immune component understudied. Here we review the evidence for activities of CD8+ T cells in immune homeostasis and regulation of autoimmune reactivity. The heterogeneous nature of identified CD8+ cell types are examined, and common phenotypes associated with functional activities are defined. The varying types of antigen signal crucial for CD8+ T cell regulatory activity are identified and the implications of these activation pathways for control of adaptive responses is considered. Finally, the promising capacity for transgenic antigen receptor directed cytotoxicity as a mechanism for modulation of autoimmunity is detailed.

CD45RC Expression of Circulating CD8+ T Cells Predicts Acute Allograft Rejection: A Cohort Study of 128 Kidney Transplant Patients

Predictive biomarkers of acute rejection (AR) are lacking. Pre-transplant expression of CD45RC on blood CD8⁺ T cells has been shown to predict AR in kidney transplant (KT) patients. The objective of the present study was to study CD45RC expression in a large cohort of KT recipients exposed to modern immunosuppressive regimens. CD45RC expression on T cells was analyzed in 128 KT patients, where 31 patients developed AR, of which 24 were found to be T-cell mediated (TCMR). Pre-transplant CD4⁺ and CD8⁺ CR45RC^high T cell proportions were significantly higher in patients with AR. The frequency of CD45RC^high T cells was significantly associated with age at transplantation but was not significantly different according to gender, history of transplantation, pre-transplant immunization, and de novo donor specific anti-Human Leucocyte Antigen (HLA) antibody. Survival-free AR was significantly better in patients with CD8⁺ CD45RC^high T cells below 58.4% (p = 0.0005), but not different according to CD4⁺ T cells (p = 0.073). According to multivariate analysis, CD8⁺ CD45RC^high T cells above 58.4% increased the risk of AR 4-fold (HR 3.96, p = 0.003). Thus, pre-transplant CD45RC expression on CD8⁺ T cells predicted AR, mainly TCMR, in KT patients under modern immunosuppressive therapies. We suggest that CD45RC expression should be evaluated in a prospective study to validate its usefulness to quantify the pre-transplant risk of AR.

Pre-transplant CD45RC expression on blood T cells differentiates patients with cancer and rejection after kidney transplantation

Background

Biological biomarkers to stratify cancer risk before kidney transplantation are lacking. Several data support that tumor development and growth is associated with a tolerant immune profile. T cells expressing low levels of CD45RC preferentially secrete regulatory cytokines and contain regulatory T cell subset. In contrast, T cells expressing high levels of CD45RC have been shown to secrete proinflammatory cytokines, to drive alloreactivity and to predict acute rejection (AR) in kidney transplant patients. In the present work, we evaluated whether pre-transplant CD45RC^low T cell subset was predictive of post-transplant cancer occurrence.

Methods

We performed an observational cohort study of 89 consecutive first time kidney transplant patients whose CD45RC T cell expression was determined by flow cytometry before transplantation. Post-transplant events including cancer, AR, and death were assessed retrospectively.

Results

After a mean follow-up of 11.1±4.1 years, cancer occurred in 25 patients (28.1%) and was associated with a decreased pre-transplant proportion of CD4⁺CD45RC^high T cells, with a frequency below 51.9% conferring a 3.7-fold increased risk of post-transplant malignancy (HR 3.71 [1.24–11.1], p = 0.019). The sensibility, specificity, negative predictive and positive predictive values of CD4⁺CD45RC^high<51.9% were 84.0, 54.7, 89.8 and 42.0% respectively. Confirming our previous results, frequency of CD8⁺CD45RC^high T cells above 52.1% was associated with AR, conferring a 20-fold increased risk (HR 21.7 [2.67–176.2], p = 0.0004). The sensibility, specificity, negative predictive and positive predictive values of CD8⁺CD45RC^high>52.1% were 94.5, 68.0, 34.7 and 98.6% respectively. Frequency of CD4⁺CD45RC^high T cells was positively correlated with those of CD8⁺CD45RC^high (p<0.0001), suggesting that recipients with high AR risk display a low cancer risk.

Conclusion

High frequency of CD45RC^high T cells was associated with AR, while low frequency was associated with cancer. Thus, CD45RC expression on T cells appears as a double-edged sword biomarker of promising interest to assess both cancer and AR risk before kidney transplantation.

Description of CD8+ Regulatory T Lymphocytes and Their Specific Intervention in Graft-versus-Host and Infectious Diseases, Autoimmunity, and Cancer

Gershon and Kondo described CD8⁺ Treg lymphocytes as the first ones with regulating activity due to their tolerance ability to foreign antigens and their capacity to inhibit the proliferation of other lymphocytes. Regardless, CD8⁺ Treg lymphocytes have not been fully described-unlike CD4⁺ Treg lymphocytes-because of their low numbers in blood and the lack of specific and accurate population markers. Still, these lymphocytes have been studied for the past 30 years, even after finding difficulties during investigations. As a result, studies have identified markers that define their subpopulations. This review is focused on the expression of cell membrane markers as CD25, CD122, CD103, CTLA-4, CD39, CD73, LAG-3, and FasL as well as soluble molecules such as FoxP3, IFN-γ, IL-10, TGF-β, IL-34, and IL-35, in addition to the lack of expression of cell activation markers such as CD28, CD127 CD45RC, and CD49d. This work also underlines the importance of identifying some of these markers in infections with several pathogens, autoimmunity, cancer, and graft-versus-host disease as a strategy in their prevention, monitoring, and cure.

Identification of potential gene targets in systemic vasculitis using DNA microarray analysis

The present study aimed to identify the involvement of critical genes in systemic vasculitis, to gain an improved understanding of the molecular circuity and to investigate novel potential gene targets for systemic vasculitis treatment. The dual-color cDNA microarray data of GSE16945, consisting of peripheral mononuclear blood cell specimens from 13 patients with systemic vasculitis and 16 healthy controls, was downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were screened in systemic vasculitis compared with controls using BRB ArrayTools, followed by the construction of a protein-protein interaction (PPI) network using the clusterProfiler package, and significant functional interaction (FI) module selection. Furthermore, transcriptional factors (TFs) among the identified DEGs were predicted and a transcriptional regulation network was constructed. A total of 173 up- and 93 downregulated genes were identified, which were mainly associated with immune response pathways. FBJ murine osteosarcoma viral oncogene homolog (FOS), ubiquitin B (UBB), signal transducer and activator of transcription 1 (STAT1) and MX dynamin-like GTPase 1 (MX1) were identified as hub proteins in the PPI network. Furthermore, UBB, FOS, and STAT1 were hub proteins in the three identified FI modules, respectively. In total, nine TFs were predicted among the DEGs. Of the DEGs that were predicted to be TFs, STAT1, v-maf avian musculoaponeurotic fibrosarcoma oncogene homolog B (MAFB) and tyrosine 3-monooxygenase/tryptophan 5-monooxygenase activation protein Z (YWHAZ), which interacted with each other, were identified to regulate further DEGs as target genes. Various genes, including FOS, UBB, MX1, STAT1, MAFB, and YWHAZ may be potential targets useful for the treatment of systemic vasculitis.

Transient antibody targeting of CD45RC induces transplant tolerance and potent antigen-specific regulatory T cells

Rat and human CD4⁺ and CD8⁺ Tregs expressing low levels of CD45RC have strong immunoregulatory properties. We describe here that human CD45 isoforms are nonredundant and identify distinct subsets of cells. We show that CD45RC is not expressed by CD4⁺ and CD8⁺ Foxp3⁺ Tregs, while CD45RA/RB/RO are. Transient administration of a monoclonal antibody (mAb) targeting CD45RC in a rat cardiac allotransplantation model induced transplant tolerance associated with inhibition of allogeneic humoral responses but maintained primary and memory responses against cognate antigens. Anti-CD45RC mAb induced rapid death of CD45RC^high T cells through intrinsic cell signaling but preserved and potentiated CD4⁺ and CD8⁺ CD45RC^low/- Tregs, which are able to adoptively transfer donor-specific tolerance to grafted recipients. Anti-CD45RC treatment results in distinct transcriptional signature of CD4⁺ and CD8⁺ CD45RC^low/- Tregs. Finally, we demonstrate that anti-human CD45RC treatment inhibited graft-versus-host disease (GVHD) in immune-humanized NSG mice. Thus, short-term anti-CD45RC is a potent therapeutic candidate to induce transplantation tolerance in human.

IL-34 is a Treg-specific cytokine and mediates transplant tolerance

Cytokines and metabolic pathway-controlling enzymes regulate immune responses and have potential as powerful tools to mediate immune tolerance. Blockade of the interaction between CD40 and CD40L induces long-term cardiac allograft survival in rats through a CD8+CD45RClo Treg potentiation. Here, we have shown that the cytokine IL-34, the immunoregulatory properties of which have not been previously studied in transplantation or T cell biology, is expressed by rodent CD8+CD45RClo Tregs and human FOXP3+CD45RCloCD8+ and CD4+ Tregs. IL-34 was involved in the suppressive function of both CD8+ and CD4+ Tregs and markedly inhibited alloreactive immune responses. Additionally, in a rat cardiac allograft model, IL-34 potently induced transplant tolerance that was associated with a total inhibition of alloantibody production. Treatment of rats with IL-34 promoted allograft tolerance that was mediated by induction of CD8+ and CD4+ Tregs. Moreover, these Tregs were capable of serial tolerance induction through modulation of macrophages that migrate early to the graft. Finally, we demonstrated that human macrophages cultured in the presence of IL-34 greatly expanded CD8+ and CD4+ FOXP3+ Tregs, with a superior suppressive potential of antidonor immune responses compared with non-IL-34-expanded Tregs. In conclusion, we reveal that IL-34 serves as a suppressive Treg-specific cytokine and as a tolerogenic cytokine that efficiently inhibits alloreactive immune responses and mediates transplant tolerance.

T cells in vascular inflammatory diseases

Inflammation of the human vasculature is a manifestation of many different diseases ranging from systemic autoimmune diseases to chronic inflammatory diseases, in which multiple types of immune cells are involved. For both autoimmune diseases and chronic inflammatory diseases several observations support a key role for T lymphocytes in these disease pathologies, but the underlying mechanisms are poorly understood. Previous studies in several autoimmune diseases have demonstrated a significant role for a specific subset of CD4⁺ T cells termed effector memory T (T_EM) cells. This expanded population of T_EM cells may contribute to tissue injury and disease progression. These cells exert multiple pro-inflammatory functions through the release of effector cytokines. Many of these cytokines have been detected in the inflammatory lesions and participate in the vasculitic reaction, contributing to recruitment of macrophages, neutrophils, dendritic cells, natural killer cells, B cells, and T cells. In addition, functional impairment of regulatory T cells paralyzes anti-inflammatory effects in vasculitic disorders. Interestingly, activation of T_EM cells is uniquely dependent on the voltage-gated potassium Kv1.3 channel providing an anchor for specific drug targeting. In this review, we focus on the CD4⁺ T cells in the context of vascular inflammation and describe the evidence supporting the role of different T cell subsets in vascular inflammation. Selective targeting of pathogenic T_EM cells might enable a more tailored therapeutic approach that avoids unwanted adverse side effects of generalized immunosuppression by modulating the effector functions of T cell responses to inhibit the development of vascular inflammation.

MHC-derived allopeptide activates TCR-biased CD8+ Tregs and suppresses organ rejection

In a rat heart allograft model, preventing T cell costimulation with CD40Ig leads to indefinite allograft survival, which is mediated by the induction of CD8+CD45RClo regulatory T cells (CD8+CD40Ig Tregs) interacting with plasmacytoid dendritic cells (pDCs). The role of TCR-MHC-peptide interaction in regulating Treg activity remains a topic of debate. Here, we identified a donor MHC class II-derived peptide (Du51) that is recognized by TCR-biased CD8+CD40Ig Tregs and activating CD8+CD40Ig Tregs in both its phenotype and suppression of antidonor alloreactive T cell responses. We generated a labeled tetramer (MHC-I RT1.Aa/Du51) to localize and quantify Du51-specific T cells within rat cardiac allografts and spleen. RT1.Aa/Du51-specific CD8+CD40Ig Tregs were the most suppressive subset of the total Treg population, were essential for in vivo tolerance induction, and expressed a biased, restricted Vβ11-TCR repertoire in the spleen and the graft. Finally, we demonstrated that treatment of transplant recipients with the Du51 peptide resulted in indefinite prolongation of allograft survival. These results show that CD8+CD40Ig Tregs recognize a dominant donor antigen, resulting in TCR repertoire alterations in the graft and periphery. Furthermore, this allopeptide has strong therapeutic activity and highlights the importance of TCR-peptide-MHC interaction for Treg generation and function.

Current understanding of the pathogenesis of granulomatosis with polyangiitis (Wegener's)

Granulomatosis with polyangiitis (Wegener's) (GPA) is a multisystem disease of unknown etiology, characterized by granulomata of the respiratory tract and systemic necrotizing vasculitis. Antineutrophil cytoplasmic antibodies (ANCA) with specificity for proteinase 3 (PR3) are a defining feature of this disease. GPA usually starts as a granulomatous disease of the respiratory tract and, in the majority of patients, progresses to systemic disease with PR3-ANCA-associated vasculitis. Today, epidemiological evidence indicates that GPA develops as a result of complex gene-environment interactions. The nature of these risk factors and pathogenic mechanisms involved, however, are only just beginning to be understood. Clinical data and in vitro experimental results point to the pathogenic pathways involved in tissue lesion development, in which ANCA, cellular immunity, neutrophils extracellular traps, fibroblasts, vascular endothelial cells and inflammatory mediators play a major role. Today, the pathophysiological significance of PR3-ANCA is still unclear and the pathogenic pathways leading to granuloma formation are not explained. New data unexpectedly suggest that the destruction of nasal cartilage in GPA is mainly mediated by fibroblasts that can be blocked by corticosteroids.

A higher risk of acute rejection of human kidney allografts can be predicted from the level of CD45RC expressed by the recipients' CD8 T cells

Although transplantation is the common treatment for end-stage renal failure, allograft rejection and marked morbidity from the use of immunosuppressive drugs remain important limitations. A major challenge in the field is to identify easy, reliable and noninvasive biomarkers allowing the prediction of deleterious alloreactive immune responses and the tailoring of immunosuppressive therapy in individuals according to the rejection risk. In this study, we first established that the expression of the RC isoform of the CD45 molecule (CD45RC) on CD4 and CD8 T cells from healthy individuals identifies functionally distinct alloreactive T cell subsets that behave differently in terms of proliferation and cytokine secretion. We then investigated whether the frequency of the recipients CD45RC T cell subsets before transplantation would predict acute graft rejection in a cohort of 89 patients who had undergone their first kidney transplantation. We showed that patients exhibiting more than 54.7% of CD8 CD45RC(high) T cells before transplantation had a 6 fold increased risk of acute kidney graft rejection. In contrast, the proportions of CD4 CD45RC T cells were not predictive. Thus, a higher risk of acute rejection of human kidney allografts can be predicted from the level of CD45RC expressed by the recipients' CD8 T cells.

Impact of bacterial colonization on exhaled inflammatory markers in wheezing preschool children

Wheeze is a common symptom in preschool children. The role of bacteria, regulatory T (T(reg)) cells and their association with airway inflammation in preschool wheeze is largely unknown. We evaluated inflammatory markers in exhaled breath condensate (EBC), bacterial colonization and circulating T(reg) cells in preschool children with and without recurrent wheeze. We recruited 252 children (aged two to four years) with (N = 202) and without (N = 50) recurrent wheeze. EBC was collected using an efficient closed glass condenser. Inflammatory markers in EBC (Interleukin(IL)-2, IL-4, IL-8, IL-10, IL-13) were assessed using multiplex immunoassay. Nasal and throat swabs were analysed for presence of Streptococcus pneumoniae, Haemophilus (para)influenzae and Staphylococcus aureus. Proportions of T(reg) cells (CD4(+)CD25(high)CD127(-)) were quantified by flow cytometry. Recurrent wheezing children had elevated EBC levels of IL-2, IL-4, IL-10 and IL-13 compared to non-wheezers (odds ratio (95% confidence interval): 1.67 (1.23-2.27): 1.58 (1.15-2.18): 1.47 (1.14-1.90): 1.55 (1.16-2.06), p <0.05, respectively). Bacteria were frequently present in children with and without wheeze, with no difference in prevalence (16-52% versus 16-50%, respectively). Moreover, the proportion of T(reg) cells did not differ between both groups. Wheezing children with bacterial colonization did not significantly differ in exhaled levels of inflammatory markers or proportion of T(reg) cells compared to wheezing children without colonization. The analysis of EBC might serve as a helpful non-invasive tool to early assess airway inflammation in wheezing children. The various elevated exhaled inflammatory markers indicate increased airway inflammation in wheezing preschool children. In the presence of wheeze, we found no evidence for bacterial induced airway inflammation.

Increased frequency of CCR4+ and CCR6+ memory T-cells including CCR7+CD45RAmed very early memory cells in granulomatosis with polyangiitis (Wegener's)

INTRODUCTION

Chemokine receptors play an important role in mediating the recruitment of T cells to inflammatory sites. Previously, small proportions of circulating Th1-type CCR5+ and Th2-type CCR3+ cells have been shown in granulomatosis with polyangiitis (GPA). Wondering to what extent CCR4 and CCR6 expression could also be implicated in T cell recruitment to inflamed sites in GPA, we investigated the expression of CCR4 and CCR6 on T cells and its association with T cell diversity and polarization.

METHODS

Multicolor flow cytometry was used to analyze CCR4, CCR6, and intracellular cytokine expression of T cells from whole blood of GPA-patients (n = 26) and healthy controls (n = 20). CCR7 and CD45RA were included for phenotypic characterization.

RESULTS

We found a significant increase in the percentages of circulating CCR4+ and CCR6+ cells within the total CD4+ T cell population in GPA. In contrast, there was no difference in the percentages of CD8+CCR4+ and CD8+CCR6+ T cells between GPA and healthy controls. CCR4 and CCR6 expression was largely confined to central (TCM) and effector memory T cells (TEM, TEMRA). A significant increase in the frequency of CCR4+ and CCR6+ TEMRA and CCR6+ TCM was shown in GPA. Of note, we could dissect CCR4 and CCR6 expressing CCR7+CD45RAmed very early memory T cells (TVEM) from genuine CCR7+CD45RAhigh naïve T cells lacking CCR4 and CCR6 expression for peripheral tissue-migration within the CCR7+CD45RA+ compartment. The frequencies of CCR4+ and CCR6+ TVEM were also significantly increased in GPA. An increased percentage of IL-17+ and IL-22+ cells was detected in the CCR6+ cell subsets and IL-4+ cells in the CRR4+ cell subset when compared with CD4+ cells lacking CCR4 and CCR6 expression.

CONCLUSIONS

Increased frequencies of circulating CCR4+ and CCR6+ memory T cell subsets including hitherto unreported TVEM suggest persistent T cell activation with the accumulation of CCR4+ and CCR6+ cells in GPA. CCR4 and CCR6 could be involved in the recruitment of T cells including cytokine-producing subsets to inflamed sites in GPA.

T-helper cells as new players in ANCA-associated vasculitides

In anti-neutrophil cytoplasmic autoantibody-associated vasculitides (AAV), several observations support a key role of T-helper cells (CD4(+) T cells) in disease pathophysiology. An expanded population of effector memory CD4(+) T cells in AAV patients may contribute to tissue injury and disease progression. In addition, functional impairment of regulatory T cells (T(Regs)) is reported in AAV patients. A fraction of T(Regs) have the capacity to differentiate into Th17 cells in the context of a proinflammatory environment. Therefore, nonfunctionality of T(Regs) described in AAV patients may be caused by their conversion into IL-17-producing cells that may contribute to granulomatous vasculitis. Further investigations directed at the plasticity of T(Regs) in AAV patients are warranted.

Differential actions of glycodelin-A on Th-1 and Th-2 cells: a paracrine mechanism that could produce the Th-2 dominant environment during pregnancy

BACKGROUND

The maternal-fetal interface has a unique immunological response towards the implanting placenta. It is generally accepted that a T-helper type-2 (Th-2) cytokine prevailing environment is important in pregnancy. The proportion of Th-2 cells in the peripheral blood and decidua is significantly higher in pregnant women in the first trimester than in non-pregnant women. Glycodelin-A (GdA) is a major endocrine-regulated decidual glycoprotein thought to be related to fetomaternal defence. Yet the relationship between its immunoregulatory activities and the shift towards Th-2 cytokine profile during pregnancy is unclear.

METHODS

GdA was immunoaffinity purified from human amniotic fluid. T-helper, T-helper type-1 (Th-1) and Th-2 cells were isolated from the peripheral blood. The viability of these cells was studied by XTT assay. Immunophenotyping of CD4/CD294, cell death and GdA-binding were determined by flow cytometry. The mRNA expression, surface expression and secretion of Fas/Fas ligand (FasL) were determined by quantitative polymerase chain reaction, flow cytometry and ELISA, respectively. The activities of caspase-3, -8 and -9 were measured. The phosphorylation of extracellular signal-regulated kinases (ERK), p38 and, c-Jun N-terminal kinase was determined by western blotting.

RESULTS

Although GdA bound to both Th-1 and Th-2 cells, it had differential actions on the two cell-types. GdA induced cell death of the Th-1 cells but not the Th-2 cells. The cell death was mediated through activation of caspase -3, -8 and -9 activities. GdA up-regulated the expression of Fas and inhibited ERK activation in the Th-1 cells, which might enhance the vulnerability of the cells to cell death caused by a trophoblast-derived FasL.

CONCLUSIONS

The data suggest that GdA could be an endometrial factor that contributes to the Th-2/Th-1 shift during pregnancy.

Phenotypic and functional characterization of CD8(+) T regulatory cells

Increasing evidence shows the presence and significance of CD8+ T regulatory cells (CD8+ Tregs) in both human and rodent transplant recipients, as well as in autoimmune disease models. We, hereafter, review all available data on the phenotypic and functional characterization of CD8+ Tregs, and we also provide detailed protocols to purify them and analyze their suppressive function. Different subsets of dendritic cells (DCs) and CD4+ effector T cells may modulate the suppression mediated by CD8+ Tregs. By analyzing the proliferation of CFSE-labeled naïve CD4+CD25- T cells in coculture MLR and transwell experiments, we explored the mutual modulation of CD8+ Tregs, DC subsets, and CD4+ T effector cells. The suppressive function of CD8+ Tregs was mediated by both cell-contact-dependent and -independent mechanisms.

Pathogenesis of ANCA-associated vasculitis

Antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) comprises a group of systemic inflammatory vasculitides associated with circulating autoantibodies directed against the neutrophil granule components proteinase 3 and myeloperoxidase. ANCA interact with their target antigens on cytokine primed neutrophils, causing neutrophil activation via several signaling pathways that culminates in endothelial interaction, degranulation, cytokine production, and endothelial and tissue damage. The presence of autoantibodies implies the assistance of autoreactive T-helper cells and B cells, and a failure of regulatory mechanisms. This article reviews the current evidence for the pathogenic mechanisms culminating in autoantibody production, the effects of ANCA-neutrophil and neutrophil-endothelial interactions, and the mechanisms of tissue damage.

T cells in ANCA-associated vasculitis: what can we learn from lesional versus circulating T cells?

Anti-neutrophil cytoplasmic antibody (ANCA) - associated vasculitis (AAV) is a life-threatening autoimmune disease characterized by an antibody-mediated glomerulonephritis and necrotizing vasculitis. Apart from antibodies, T cells are also involved in disease pathogenesis. This review stresses the hallmarks of T cell-mediated pathology in AAV and highlights the characteristics of lesional and circulating T cells in the immune response in AAV. Circulating effector T-cell populations are expanded and are in a persistent state of activation. Circulating regulatory T-cell subsets are less well characterized but seem to be impaired in function. Lesional effector T cells are present in granulomas, vasculitic lesions, and nephritis. Lesional T cells usually show pro-inflammatory properties and promote granuloma formation. Apart from T cells, dendritic cells are abundantly present at the sites of inflammation and locally orchestrate the immune response. Targeting the above-mentioned T cell-mediated disease mechanisms will potentially provide powerful therapeutic tools for AAV.

Vitamin D status is positively correlated with regulatory T cell function in patients with multiple sclerosis

BACKGROUND

In several autoimmune diseases, including multiple sclerosis (MS), a compromised regulatory T cell (Treg) function is believed to be critically involved in the disease process. In vitro, the biologically active metabolite of vitamin D has been shown to promote Treg development. A poor vitamin D status has been linked with MS incidence and MS disease activity. In the present study, we assess a potential in vivo correlation between vitamin D status and Treg function in relapsing remitting MS (RRMS) patients.

METHODOLOGY/PRINCIPAL FINDINGS

Serum levels of 25-hydroxyvitamin D (25(OH)D) were measured in 29 RRMS patients. The number of circulating Tregs was assessed by flow-cytometry, and their functionality was tested in vitro in a CFSE-based proliferation suppression assay. Additionally, the intracellular cytokine profile of T helper cells was determined directly ex-vivo by flow-cytometry. Serum levels of 25(OH)D correlated positively with the ability of Tregs to suppress T cell proliferation (R = 0.590, P = 0.002). No correlation between 25(OH)D levels and the number of Tregs was found. The IFN-gamma/IL-4 ratio (Th1/Th2-balance) was more directed towards IL-4 in patients with favourable 25(OH)D levels (R = -0.435, P = 0.023).

CONCLUSIONS/SIGNIFICANCE

These results show an association of high 25(OH)D levels with an improved Treg function, and with skewing of the Th1/Th2 balance towards Th2. These findings suggest that vitamin D is an important promoter of T cell regulation in vivo in MS patients. It is tempting to speculate that our results may not only hold for MS, but also for other autoimmune diseases. Future intervention studies will show whether modulation of vitamin D status results in modulation of the T cell response and subsequent amelioration of disease activity.