Maintenance of immune tolerance by Foxp3+ regulatory T cells requires CD69 expression

Regulatory T-cell frequency and function in acute myocardial infarction patients and its correlation with ventricular dysfunction

A high percentage of patients with acute coronary syndrome develop heart failure due to the ischemic event. Regulatory T (Treg) cells are lymphocytes with suppressive capacity that control the immune response and include the conventional CD4+ CD25hi Foxp3+ cells and the CD4+ CD25var CD69+ LAP+ Foxp3- IL-10+ cells. No human follow-up studies focus on Treg cells' behavior after infarction and their possible relationship with ventricular function as a sign of postischemic cardiac remodeling. This study aimed to analyze, by flow cytometry, the circulating levels of CD69+ Treg cells and CD4+ CD25hi Foxp3+ cells, their IL-10+ production as well as their function in patients with acute myocardial infarction (AMI), and its possible relation with ventricular dysfunction. We found a significant difference in the percentage of CD4+ CD25hi Foxp3+ cells and IL-10+ MFI in patients with AMI at 72 hours compared with the healthy control group, and the levels of these cells were reduced 6 months post-AMI. Regarding the suppressive function of CD4+ CD25+ regulatory cells, they were dysfunctional at 3 and 6 months post-AMI. The frequency of CD69+ Treg cells was similar between patients with AMI at 72 hours postinfarction and the control groups. Moreover, the frequency of CD69+ Treg cells at 3 and 6 months postischemic event did not vary over time. Treg cells play a role in regulating inflammation after an AMI, and its function may be compromised in this pathology. This work is the first report to evaluate CD69+ Foxp3- Treg cells in AMI patients.

Beyond FOXP3: a 20-year journey unravelling human regulatory T-cell heterogeneity

The initial idea of a distinct group of T-cells responsible for suppressing immune responses was first postulated half a century ago. However, it is only in the last three decades that we have identified what we now term regulatory T-cells (Tregs), and subsequently elucidated and crystallized our understanding of them. Human Tregs have emerged as essential to immune tolerance and the prevention of autoimmune diseases and are typically contemporaneously characterized by their CD3+CD4+CD25high CD127lowFOXP3+ phenotype. It is important to note that FOXP3+ Tregs exhibit substantial diversity in their origin, phenotypic characteristics, and function. Identifying reliable markers is crucial to the accurate identification, quantification, and assessment of Tregs in health and disease, as well as the enrichment and expansion of viable cells for adoptive cell therapy. In our comprehensive review, we address the contributions of various markers identified in the last two decades since the master transcriptional factor FOXP3 was identified in establishing and enriching purity, lineage stability, tissue homing and suppressive proficiency in CD4+ Tregs. Additionally, our review delves into recent breakthroughs in innovative Treg-based therapies, underscoring the significance of distinct markers in their therapeutic utilization. Understanding Treg subsets holds the key to effectively harnessing human Tregs for immunotherapeutic approaches.

Immunomodulatory function of licensed human bone marrow mesenchymal stromal cell-derived apoptotic bodies

BACKGROUND

Mesenchymal stromal cells (MSCs) show great potential for immunomodulatory and anti-inflammatory treatments. Clinical trials have been performed for the treatment of Type 1 diabetes, graft-versus-host disease and organ transplantation, which offer a promise of MSCs as an immunomodulatory therapy. Nevertheless, their unstable efficacy and immunogenicity concerns present challenges to clinical translation. It has emerged that the MSC-derived secretome, which includes secreted proteins, exosomes, apoptotic bodies (ABs) and other macromolecules, may have similar therapeutic effects to parent MSCs. Among all of the components of the MSC-derived secretome, most interest thus far has been garnered by exosomes for their therapeutic potential. However, since MSCs were reported to undergo apoptosis after in vivo transplantation and release ABs, we speculated as to whether ABs have immunomodulatory effects. In this study, cytokine licensing was used to enhance the immunomodulatory potency of MSCs and ABs derived from licensed MSCs in vitro were isolated to explore their immunomodulatory effects as an effective non-viable cell therapy.

RESULTS

IFN-γ and IFN-γ/TGF-β1 licensing enhanced the immunomodulatory effect of MSCs on T cell proliferation. Further, TGF-β1 and IFN-γ licensing strengthened the immunomodulatory effect of MSC on reducing the TNF-α and IL-1β expression by M1 macrophage-like THP-1 cells. Additionally, we discovered the immunomodulatory effect mediated by MSC-derived apoptotic bodies. Licensing impacted the uptake of ABs by recipient immune cells and importantly altered their phenotypes.

CONCLUSION

ABs derived from IFN-γ/TGF-β1-licensed apoptotic MSCs significantly inhibited T cell proliferation, induced more regulatory T cells, and maintained immunomodulatory T cells but reduced pro-inflammatory T cells.

IL1R1+ cancer-associated fibroblasts drive tumor development and immunosuppression in colorectal cancer

Fibroblasts have a considerable functional and molecular heterogeneity and can play various roles in the tumor microenvironment. Here we identify a pro-tumorigenic IL1R1⁺, IL-1-high-signaling subtype of fibroblasts, using multiple colorectal cancer (CRC) patient single cell sequencing datasets. This subtype of fibroblasts is linked to T cell and macrophage suppression and leads to increased cancer cell growth in 3D co-culture assays. Furthermore, both a fibroblast-specific IL1R1 knockout and IL-1 receptor antagonist Anakinra administration reduce tumor growth in vivo. This is accompanied by reduced intratumoral Th17 cell infiltration. Accordingly, CRC patients who present with IL1R1-expressing cancer-associated-fibroblasts (CAFs), also display elevated levels of immune exhaustion markers, as well as an increased Th17 score and an overall worse survival. Altogether, this study underlines the therapeutic value of targeting IL1R1-expressing CAFs in the context of CRC.

Immuno-PET Imaging of CD69 Visualizes T-Cell Activation and Predicts Survival Following Immunotherapy in Murine Glioblastoma

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. Immunotherapy may be promising for the treatment of some patients with GBM; however, there is a need for noninvasive neuroimaging techniques to predict immunotherapeutic responses. The effectiveness of most immunotherapeutic strategies requires T-cell activation. Therefore, we aimed to evaluate an early marker of T-cell activation, CD69, for its use as an imaging biomarker of response to immunotherapy for GBM. Herein, we performed CD69 immunostaining on human and mouse T cells following in vitro activation and post immune checkpoint inhibitors (ICI) in an orthotopic syngeneic mouse glioma model. CD69 expression on tumor-infiltrating leukocytes was assessed using single-cell RNA sequencing (scRNA-seq) data from patients with recurrent GBM receiving ICI. Radiolabeled CD69 Ab PET/CT imaging (CD69 immuno-PET) was performed on GBM-bearing mice longitudinally to quantify CD69 and its association with survival following immunotherapy. We show CD69 expression is upregulated upon T-cell activation and on tumor-infiltrating lymphocytes (TIL) in response to immunotherapy. Similarly, scRNA-seq data demonstrated elevated CD69 on TILs from patients with ICI-treated recurrent GBM as compared with TILs from control cohorts. CD69 immuno-PET studies showed a significantly higher tracer uptake in the tumors of ICI-treated mice compared with controls. Importantly, we observed a positive correlation between survival and CD69 immuno-PET signals in immunotherapy-treated animals and established a trajectory of T-cell activation by virtue of CD69-immuno-PET measurements. Our study supports the potential use of CD69 immuno-PET as an immunotherapy response assessment imaging tool for patients with GBM.

Significance

Immunotherapy may hold promise for the treatment of some patients with GBM. There is a need to assess therapy responsiveness to allow the continuation of effective treatment in responders and to avoid ineffective treatment with potential adverse effects in the nonresponders. We demonstrate that noninvasive PET/CT imaging of CD69 may allow early detection of immunotherapy responsiveness in patients with GBM.

Functional heterogeneity of human skin-resident memory T cells in health and disease

The human skin is populated by a diverse pool of memory T cells, which can act rapidly in response to pathogens and cancer antigens. Tissue-resident memory T cells (TRM ) have been implicated in range of allergic, autoimmune and inflammatory skin diseases. Clonal expansion of cells with TRM properties is also known to contribute to cutaneous T-cell lymphoma. Here, we review the heterogeneous phenotypes, transcriptional programs, and effector functions of skin TRM . We summarize recent studies on TRM formation, longevity, plasticity, and retrograde migration and contextualize the findings to skin TRM and their role in maintaining skin homeostasis and altered functions in skin disease.

Liposomes loaded with vitamin D3 induce regulatory circuits in human dendritic cells

Introduction

Nanomedicine provides a promising platform for manipulating dendritic cells (DCs) and the ensuing adaptive immune response. For the induction of regulatory responses, DCs can be targeted in vivo with nanoparticles incorporating tolerogenic adjuvants and auto-antigens or allergens.

Methods

Here, we investigated the tolerogenic effect of different liposome formulations loaded with vitamin D3 (VD3). We extensively phenotyped monocyte-derived DCs (moDCs) and skin DCs and assessed DC-induced regulatory CD4+ T cells in coculture.

Results

Liposomal VD3 primed-moDCs induced the development of regulatory CD4+ T cells (Tregs) that inhibited bystander memory T cell proliferation. Induced Tregs were of the FoxP3+ CD127low phenotype, also expressing TIGIT. Additionally, liposome-VD3 primed moDCs inhibited the development of T helper 1 (Th1) and T helper 17 (Th17) cells. Skin injection of VD3 liposomes selectively stimulated the migration of CD14+ skin DCs.

Discussion

These results suggest that nanoparticulate VD3 is a tolerogenic tool for DC-mediated induction of regulatory T cell responses.

Unraveling CD69 signaling pathways, ligands and laterally associated molecules

CD69 is an early leukocyte activation marker involved in the regulation of the immune response. Initial in vitro studies evaluated its function using monoclonal antibodies until knock-out mice were developed. Subsequently, four ligands for CD69 have been identified, namely galectin-1, S100A8/S100A9 complex, myosin light chains 9 and 12, and oxidized low-density lipoproteins. In addition, several molecules are laterally associated with and regulated by CD69, including calreticulin and two transmembrane receptors, sphingosine-1-phosphate receptor (S1P1) and the heterodimeric amino acid transporter complex SLC7A5-SLC3A2 (LAT1-CD98). Recently, CD69 engagement has been shown to induce the expression of the immunoregulatory receptor programmed cell death-1 (PD-1) in T cells. The molecular signaling induced by CD69 has been explored in different scenarios and cell types. This review provides a perspective on the molecular pathways, ligands and cellular functions known to be regulated by CD69.

Hypoxia-Driven Changes in a Human Intestinal Organoid Model and the Protective Effects of Hydrolyzed Whey

Many whey proteins, peptides and protein-derived amino acids have been suggested to improve gut health through their anti-oxidant, anti-microbial, barrier-protective and immune-modulating effects. Interestingly, although the degree of hydrolysis influences peptide composition and, thereby, biological function, this important aspect is often overlooked. In the current study, we aimed to investigate the effects of whey protein fractions with different degrees of enzymatic hydrolysis on the intestinal epithelium in health and disease with a novel 2D human intestinal organoid (HIO) monolayer model. In addition, we aimed to assess the anti-microbial activity and immune effects of the whey protein fractions. Human intestinal organoids were cultured from adult small intestines, and a model enabling apical administration of nutritional components during hypoxia-induced intestinal inflammation and normoxia (control) in crypt-like and villus-like HIO was established. Subsequently, the potential beneficial effects of whey protein isolate (WPI) and two whey protein hydrolysates with a 27.7% degree of hydrolysis (DH28) and a 50.9% degree of hydrolysis (DH51) were assessed. In addition, possible immune modulatory effects on human peripheral immune cells and anti-microbial activity on four microbial strains of the whey protein fractions were investigated. Exposure to DH28 prevented paracellular barrier loss of crypt-like HIO following hypoxia-induced intestinal inflammation with a concomitant decrease in hypoxia inducible factor 1 alpha (HIF1α) mRNA expression. WPI increased Treg numbers and Treg expression of cluster of differentiation 25 (CD25) and CD69 and reduced CD4+ T cell proliferation, whereas no anti-microbial effects were observed. The observed biological effects were differentially mediated by diverse whey protein fractions, indicating that (degree of) hydrolysis influences their biological effects. Moreover, these new insights may provide opportunities to improve immune tolerance and promote intestinal health.

HSF1 promotes CD69+ Treg differentiation to inhibit colitis progression

Regulatory T cells (Tregs) are critical for generating and maintaining peripheral tolerance. Treg-based immunotherapy is valuable for the clinical management of diseases resulting from dysregulation of immune tolerance. However, the lack of potency is a potential limitation of Treg therapy. In addition, CD69 positive-Treg (CD69⁺ Treg) represent a newly identified subset of Tregs with potent immune suppressive capability. Methods: Foxp3 ^YFP-Cre CD69 ^fl/fl and CD4 ^Cre CD69 ^fl/fl mice were generated to determine the relevance of CD69 to Treg. Chromatin Immunoprecipitation Assay (ChIP) and luciferase Assay were performed to detect the regulation of CD69 transcription by heat shock transcription factor 1(HSF1). Gene expression was measured by western blotting and qRT-PCR. The differentiation of naive T cells to CD69⁺Foxp3⁺ iTregs was determined by flow cytometry. The immunosuppressive ability of Tregs was analyzed by ELISA and flow cytometry. Colon inflammation in mice was reflected by changes in body weight and colon length, the disease activity index (DAI), and H&E staining of colon tissues. Results: Induced Tregs (iTregs) from CD4 ^Cre CD69 ^fl/fl mice failed to alleviate colitis. The transcription factor HSF1 interacted with the promoter of the CD69 gene to prompt its transcription during Treg differentiation. Genetic and chemical inhibition of HSF1 impaired CD69⁺ Treg differentiation and promoted the pathogenesis of colitis in mice. In contrast, HSF1 protein stabilized by inhibiting its proteasomal degradation promoted CD69⁺ Treg differentiation and alleviated colitis in mice. Moreover, adoptive transfer of iTregs with HSF1 stabilization by proteasome inhibitor (PSI) dramatically prevented the development of colitis in mice and was accompanied by decreased production of pro-inflammatory cytokines and reduced accumulation of pro-inflammatory lymphocytes in colitis tissue, whereas Tregs induced in the absence of PSI were less stable and ineffective in suppressing colitis. Conclusions: HSF1 promotes CD69⁺ Tregs differentiation by activating the CD69 transcription, which is critical for the immunosuppressive function of Tregs. Stabilization of HSF1 by PSIs results in the efficient generation of Tregs with high potency to treat colitis and probably other autoimmune diseases involving Tregs deficiency.

CD69-oxLDL ligand engagement induces Programmed Cell Death 1 (PD-1) expression in human CD4 + T lymphocytes

The mechanisms that control the inflammatory–immune response play a key role in tissue remodelling in cardiovascular diseases. T cell activation receptor CD69 binds to oxidized low-density lipoprotein (oxLDL), inducing the expression of anti-inflammatory NR4A nuclear receptors and modulating inflammation in atherosclerosis. To understand the downstream T cell responses triggered by the CD69-oxLDL binding, we incubated CD69-expressing Jurkat T cells with oxLDL. RNA sequencing revealed a differential gene expression profile dependent on the presence of CD69 and the degree of LDL oxidation. CD69-oxLDL binding induced the expression of NR4A receptors (NR4A1 and NR4A3), but also of PD-1. These results were confirmed using oxLDL and a monoclonal antibody against CD69 in CD69-expressing Jurkat and primary CD4 + lymphocytes. CD69-mediated induction of PD-1 and NR4A3 was dependent on NFAT activation. Silencing NR4A3 slightly increased PD-1 levels, suggesting a potential regulation of PD-1 by this receptor. Moreover, expression of PD-1, CD69 and NR4A3 was increased in human arteries with chronic inflammation compared to healthy controls, with a strong correlation between PD-1 and CD69 mRNA expression (r = 0.655 P < 0.0001). Moreover, PD-1 was expressed in areas enriched in CD3 infiltrating T cells. Our results underscore a novel mechanism of PD-1 induction independent of TCR signalling that might contribute to the role of CD69 in the modulation of inflammation and vascular remodelling in cardiovascular diseases.

Decoding lymphomyeloid divergence and immune hyporesponsiveness in G-CSF-primed human bone marrow by single-cell RNA-seq

Granulocyte colony-stimulating factor (G-CSF) has been widely used to mobilize bone marrow hematopoietic stem/progenitor cells for transplantation in the treatment of hematological malignancies for decades. Additionally, G-CSF is also accepted as an essential mediator in immune regulation, leading to reduced graft-versus-host disease following transplantation. Despite the important clinical roles of G-CSF, a comprehensive, unbiased, and high-resolution survey into the cellular and molecular ecosystem of the human G-CSF-primed bone marrow (G-BM) is lacking so far. Here, we employed single-cell RNA sequencing to profile hematopoietic cells in human bone marrow from two healthy donors before and after 5-day G-CSF administration. Through unbiased bioinformatics analysis, our data systematically showed the alterations in the transcriptional landscape of hematopoietic cells in G-BM, and revealed that G-CSF-induced myeloid-biased differentiation initiated from the stage of lymphoid-primed multipotent progenitors. We also illustrated the cellular and molecular basis of hyporesponsiveness of T cells and natural killer (NK) cells caused by G-CSF stimulation, including the potential direct mechanisms and indirect regulations mediated by ligand–receptor interactions. Taken together, our data extend the understanding of lymphomyeloid divergence and potential mechanisms involved in hyporesponsiveness of T and NK cells in human G-BM, which might provide basis for optimization of stem cell transplantation in hematological malignancy treatment.

Influence of air pollutants on circulating inflammatory cells and microRNA expression in acute myocardial infarction

Air pollutants increase the risk and mortality of myocardial infarction (MI). The aim of this study was to assess the inflammatory changes in circulating immune cells and microRNAs in MIs related to short-term exposure to air pollutants. We studied 192 patients with acute coronary syndromes and 57 controls with stable angina. For each patient, air pollution exposure in the 24-h before admission, was collected. All patients underwent systematic circulating inflammatory cell analyses. According to PM_2.5 exposure, 31 patients were selected for microRNA analyses. STEMI patients exposed to PM_2.5 showed a reduction of CD4⁺ regulatory T cells. Furthermore, in STEMI patients the exposure to PM_2.5 was associated with an increase of miR-146a-5p and miR-423-3p. In STEMI and NSTEMI patients PM_2.5 exposure was associated with an increase of miR-let-7f-5p. STEMI related to PM_2.5 short-term exposure is associated with changes involving regulatory T cells, miR-146a-5p and miR-423-3p.

Investigating the Potential of Isolating and Expanding Tumour-Infiltrating Lymphocytes from Adult Sarcoma

Simple Summary

Sarcomas are rare cancers that arise from connective tissue. There are more than 50 subtypes, many of which are associated with a high risk of metastasis and poor prognosis. Subtype-specific treatment is limited and conventional treatment for advanced disease has varying effects across individuals and tumour subtypes. Adoptive cell therapy shows potential to provide more personalized treatment; this study aims to explore the potential of using tumour-infiltrating lymphocytes (TIL) to treat sarcoma. We optimized a sarcoma-specific expansion protocol and successfully expanded TILs from 54 of 92 sarcoma specimens. We characterized primarily CD4⁺ and CD8⁺ T-cells in the expanded TIL cultures and demonstrated their reactivity to general stimuli. Although sarcomas in general do not have abundant lymphocytic infiltration, our expansion protocol allowed for successful expansions of viable and reactive lymphocytes, thus showing the prospects of adopting TIL therapy in sarcoma.

Abstract

Sarcomas are a heterogeneous group of mesenchymal neoplasms, many of which are associated with a high risk of metastasis and poor prognosis. Conventional chemotherapy and targeted therapies have varying effects across individuals and tumour subtypes. The current therapies frequently provide limited clinical benefit; hence, more effective treatments are urgently needed. Recent advances in immunotherapy, such as checkpoint inhibition or adoptive cell therapy (ACT), show potential in increasing efficacy by providing a more personalized treatment. Therapy with tumour-infiltrating lymphocytes (TILs) is an emerging field in immunotherapy. Here, we collected 190 sarcoma tumour specimens from patients without pre-operative adjuvant treatment in order to isolate TILs. We compared different methods of TIL expansion and optimized a protocol specifically for efficacy in culturing TILs from sarcoma. The expanded TIL populations were characterized by flow cytometry analysis using CD3, CD4, CD8, CD14, CD19 and CD56 markers. The TIL populations were non-specifically stimulated to establish TIL reactivity. Through an optimized expansion protocol, TILs were isolated and cultured from 54 of 92 primary sarcoma specimens. The isolated TILs varied in CD4⁺ and CD8⁺ T-cell compositions and retained their ability to release IFNγ upon stimulation. Our results suggest that certain sarcoma subtypes have the potential to yield a sufficient number of TILs for TIL therapy.

SARS-CoV-2 Proteome Harbors Peptides Which Are Able to Trigger Autoimmunity Responses: Implications for Infection, Vaccination, and Population Coverage

Autoimmune diseases (ADs) could occur due to infectious diseases and vaccination programs. Since millions of people are expected to be infected with SARS-CoV-2 and vaccinated against it, autoimmune consequences seem inevitable. Therefore, we have investigated the whole proteome of the SARS-CoV-2 for its ability to trigger ADs. In this regard, the entire proteome of the SARS-CoV-2 was chopped into more than 48000 peptides. The produced peptides were searched against the entire human proteome to find shared peptides with similar experimentally confirmed T-cell and B-cell epitopes. The obtained peptides were checked for their ability to bind to HLA molecules. The possible population coverage was calculated for the most potent peptides. The obtained results indicated that the SARS-CoV-2 and human proteomes share 23 peptides originated from ORF1ab polyprotein, nonstructural protein NS7a, Surface glycoprotein, and Envelope protein of SARS-CoV-2. Among these peptides, 21 peptides had experimentally confirmed equivalent epitopes. Amongst, only nine peptides were predicted to bind to HLAs with known global allele frequency data, and three peptides were able to bind to experimentally confirmed HLAs of equivalent epitopes. Given the HLAs which have already been reported to be associated with ADs, the ESGLKTIL, RYPANSIV, NVAITRAK, and RRARSVAS were determined to be the most harmful peptides of the SARS-CoV-2 proteome. It would be expected that the COVID-19 pandemic and the vaccination against this pathogen could significantly increase the ADs incidences, especially in populations harboring HLA-B*08:01, HLA-A*024:02, HLA-A*11:01 and HLA-B*27:05. The Southeast Asia, East Asia, and Oceania are at higher risk of AD development.

Characteristics of Circulatory γδ T cells in Patients with Symptomatic Chronic Hepatitis B Infection

Hepatitis B is a viral infection that can cause serious liver disease. Chronic hepatitis B (CHB) infection places individuals at higher risk of developing cirrhosis of the liver and hepatocellular cancer. Immune dysfunction, including altered distribution and functional status of T cell immunity, is a contributor to hepatitis B virus (HBV) pathogenesis. In this study, we examined the distribution of circulating γδ T cell subpopulations and levels of cell surface expression of suppressive markers on γδ T cells in individuals with CHB infection and clinical liver disease. A significantly higher proportion of terminally differentiated (T_EMRA) (CD27^-CD45RA⁺) γδ T cells along with significantly lower percentages of central memory (CD27⁺CD45RA^-) and effector memory (CD27^-CD45RA^-) γδ T cells were observed in peripheral blood of these individuals. The expression of exhaustion markers-Tim-3 and Lag-3 was elevated in γδ T cells from CHB-infected individuals compared with healthy controls (HC) and blockade of these exhaustion markers resulted in restoration of interferon gamma (IFN-γ) secretion by γδ T cells. In addition, γδ T cells from CHB patients expressed increased levels of CD69, another important regulator of immune responses. Together, these results suggest that CHB patients with clinical sign of liver disease have T_EMRA γδ T cells with a potentially exhausted phenotype that may in turn impair their immunoregulatory role and facilitate pathogenesis of CHB disease.

Tofacitinib downregulates antiviral immune defence in keratinocytes and reduces T cell activation

BACKGROUND

Tofacitinib is a novel Janus kinase (JAK) inhibitor approved for the treatment of rheumatoid arthritis, psoriatic arthritis, and ulcerative colitis. In clinical trials, the most common adverse events observed were nasopharyngitis, upper respiratory tract infections, and zoster. JAKs are found downstream of the type II cytokine receptor family used by a number of T_H17 cell-associated cytokines for signal transduction. These cytokines lead to the secretion of antiviral and antimicrobial peptides (AMPs) by keratinocytes or synoviocytes. Blocking the JAK pathway might result in a diminished secretion of antimicrobial and antiviral peptides causing higher susceptibility to infections in patients treated with JAK inhibitors.

METHODS

We treated primary human keratinocytes and synoviocytes with tofacitinib and subsequently added various cytokines and bacterial surface proteins before evaluation of the response via RT-qPCR. CD69 expression on tofacitinib-treated PBMCs was investigated via flow cytometry.

RESULTS

We found a markedly reduced gene expression of all tested antiviral peptides such as MX1 or ISG15 in keratinocytes and synoviocytes in the presence of tofacitinib in vitro. Additionally, we found that JAK inhibition reduced activation of T cells after stimulation with bacterial LPS or viral VZV gE.

CONCLUSIONS

The antiviral immunity is strongly inhibited in the presence of tofacitinib in vitro, while the antimicrobial immunity does not seem to be affected. In T cells, the overall activation process seems to be influenced by tofacitinib. These findings suggest that tofacitinib has an impact on antiviral immunity such as patients treated with tofacitinib often show adverse events like herpes zoster.

Everolimus, an mTORC1/2 inhibitor, in ART-suppressed individuals who received solid organ transplantation: A prospective study

Pharmacologic inhibition of the mammalian target of rapamycin (mTOR) in the setting of renal transplantation has previously been associated with lower human immunodeficiency virus 1 (HIV-1) DNA burden, and in vitro studies suggest that mTOR inhibition may lead to HIV transcriptional silencing. Because prospective clinical trials are lacking, we conducted an open-label, single-arm study to determine the impact of the broad mTOR inhibitor, everolimus, on residual HIV burden, transcriptional gene expression profiles, and immune responses in HIV-infected adult solid organ transplant (SOT) recipients on antiretroviral therapy. Whereas everolimus therapy did not have an overall effect on cell-associated HIV-1 DNA and RNA levels in the entire cohort, participants who maintained everolimus time-averaged trough levels >5 ng/mL during the first 2 months of therapy had significantly lower RNA levels up to 6 months after the cessation of study drug. Time-averaged everolimus trough levels significantly correlated with greater inhibition of mTOR gene pathway transcriptional activity. Everolimus treatment also led to decreased PD-1 expression on certain T cell subsets. These data support the rationale for further study of the effects of mTOR inhibition on HIV transcriptional silencing in non-SOT populations, either alone or in combination with other strategies. Trial Registration: ClinicalTrials.gov NCT02429869.

An examination of the relationship between regulatory T cells and symptom flare-ups in children and adolescents diagnosed with chronic tic disorder and Tourette syndrome

BACKGROUND

Tourette syndrome (TS) is a childhood-onset neurodevelopmental disorder characterized by several motor and phonic tics.

AIMS

In this study, we aimed to compare activated regulatory T cell (Treg) values between patients with TS/chronic tic disorder (CTD) and age- and sex-matched healthy controls (HCs).

MATERIALS AND METHOD

Patients with TS/CTD and age- and sex-matched HCs were included in the study. The severity of the disease was evaluated using the Yale Global Tic Severity Scale. CD4⁺CD25⁺CD127^low Tregs from the patient group and the control group were compared using flow cytometry.

RESULTS

The study included 48 patients diagnosed with TS/CTD (36 males and 12 females, mean age: 11.58 ± 2.61) and 24 HCs (18 males and 6 females, mean age: 11.63 ± 2.60). The TS/CTD group had significantly higher activated regulatory T percentile with respect to the T helper value compared to the HCs (p = 0.010). Lymphocyte count, T lymphocyte count, T lymphocyte percentage, T-helper lymphocyte count, and T-helper lymphocyte percentage were lower in the patient group compared to the control group (p = 0.024, 0.003, 0.007, <0.001, <0.001, respectively). The comparison of three groups (mild, moderate-severe, and HCs) revealed that T lymphocyte number and percentage and the T helper number and percentage were significantly higher in the HC group compared to the moderate-severe group, whereas the activated Treg percentage with respect to the T helper value was significantly higher in the moderate-severe group compared to the HC group (0.002, 0.026, <0.001, <0.001, 0.027, respectively).

CONCLUSION

Our results suggest that Tregs may have a role in the pathogenesis of TS/CTD.

Erythroid Differentiation Regulator 1 Ameliorates Collagen-Induced Arthritis via Activation of Regulatory T Cells

Erythroid differentiation regulator 1 (Erdr1) has been identified as an anti-inflammatory factor in several disease models, including collagen-induced arthritis (CIA), but its exact mechanisms are still not fully understood. Here, the involvement of regulatory T (Treg) cells in Erdr1-improved CIA was investigated. In the CIA model, Erdr1 was confirmed to reduce collagen-specific IgM in plasma and plasma cells in draining lymph nodes. Importantly, the downregulated Treg cell ratio in draining lymph nodes from CIA mice was recovered by Erdr1 treatment. In addition, administration of Erdr1 improved the CIA score and joint tissue damage, while it revealed no effect in Treg cell-depleted CIA mice, indicating that Treg cells mediate the therapeutic effects of Erdr1 in the CIA model. Results from in vitro experiments also demonstrated that Erdr1 significantly induced Treg cell differentiation and the expression of Treg activation markers, including CD25, CD69, and CTLA4 in CD4⁺Foxp3⁺ cells. Furthermore, Erdr1-activated Treg cells dramatically suppressed the proliferation of responder T cells, suggesting that they are functionally active. Taken together, these results show that Erdr1 induces activation of Treg cells and ameliorates rheumatoid arthritis via Treg cells.

Novel human immunomodulatory T cell receptors and their double-edged potential in autoimmunity, cardiovascular disease and cancer

In the last decade, approaches based on T cells and their immunomodulatory receptors have emerged as a solid improvement in treatments for various types of cancer. However, the roles of these molecules in the therapeutic context of autoimmune and cardiovascular diseases are still relatively unexplored. Here, we review the best known and most commonly used immunomodulatory T cell receptors in clinical practice (PD-1 and CTLA-4), along with the rest of the receptors with known functions in animal models, which have great potential as modulators in human pathologies in the medium term. Among these other receptors is the receptor CD69, which has recently been described to be expressed in mouse and human T cells in autoimmune and cardiovascular diseases and cancer. However, inhibition of these receptors individually or in combination by drugs or monoclonal antibodies generates a loss of immunological tolerance and can trigger multiple autoimmune disorders in different organs and immune-related adverse effects. In the coming decades, knowledge on the functions of different immunomodulatory receptors will be pivotal for the development of new and better therapies with less harmful side effects. In this review, we discuss the roles of these receptors in the control of immunity from a perspective focused on therapeutic potential in not only cancer but also autoimmune diseases, such as systemic lupus erythematosus, autoimmune diabetes and rheumatoid arthritis, and cardiovascular diseases, such as atherosclerosis, acute myocardial infarction, and myocarditis.

Enhanced antitumor immunity through sequential targeting of PI3Kδ and LAG3

BACKGROUND

Despite striking successes, immunotherapies aimed at increasing cancer-specific T cell responses are unsuccessful in most patients with cancer. Inactivating regulatory T cells (Treg) by inhibiting the PI3Kδ signaling enzyme has shown promise in preclinical models of tumor immunity and is currently being tested in early phase clinical trials in solid tumors.

METHODS

Mice bearing 4T1 mammary tumors were orally administered a PI3Kδ inhibitor (PI-3065) daily and tumor growth, survival and T cell infiltrate were analyzed in the tumor microenvironment. A second treatment schedule comprised PI3Kδ inhibitor with anti-LAG3 antibodies administered sequentially 10 days later.

RESULTS

As observed in human immunotherapy trials with other agents, immunomodulation by PI3Kδ-blockade led to 4T1 tumor regressor and non-regressor mice. Tumor infiltrating T cells in regressors were metabolically fitter than those in non-regressors, with significant enrichments of antigen-specific CD8+ T cells, T cell factor 1 (TCF1)+ T cells and CD69- T cells, compatible with induction of a sustained tumor-specific T cell response. Treg numbers were significantly reduced in both regressor and non-regressor tumors compared with untreated tumors. The remaining Treg in non-regressor tumors were however significantly enriched with cells expressing the coinhibitory receptor LAG3, compared with Treg in regressor and untreated tumors. This striking difference prompted us to sequentially block PI3Kδ and LAG3. This combination enabled successful therapy of all mice, demonstrating the functional importance of LAG3 in non-regression of tumors on PI3Kδ inhibition therapy. Follow-up studies, performed using additional cancer cell lines, namely MC38 and CT26, indicated that a partial initial response to PI3Kδ inhibition is an essential prerequisite to a sequential therapeutic benefit of anti-LAG3 antibodies.

CONCLUSIONS

These data indicate that LAG3 is a key bottleneck to successful PI3Kδ-targeted immunotherapy and provide a rationale for combining PI3Kδ/LAG3 blockade in future clinical studies.

Regulatory T Cell Plasticity and Stability and Autoimmune Diseases

CD4⁺CD25⁺ regulatory T cells (Tregs) are a class of CD4⁺ T cells with immunosuppressive functions that play a critical role in maintaining immune homeostasis. However, in certain disease settings, Tregs demonstrate plastic differentiation, and the stability of these Tregs, which is characterized by the stable expression or protective epigenetic modifications of the transcription factor Foxp3, becomes abnormal. Plastic Tregs have some features of helper T (Th) cells, such as the secretion of Th-related cytokines and the expression of specific transcription factors in Th cells, but also still retain the expression of Foxp3, a feature of Tregs. Although such Th-like Tregs can secrete pro-inflammatory cytokines, they still possess a strong ability to inhibit specific Th cell responses. Therefore, the plastic differentiation of Tregs not only increases the complexity of the immune circumstances under pathological conditions, especially autoimmune diseases, but also shows an association with changes in the stability of Tregs. The plastic differentiation and stability change of Tregs play vital roles in the progression of diseases. This review focuses on the phenotypic characteristics, functions, and formation conditions of several plastic Tregs and also summarizes the changes of Treg stability and their effects on inhibitory function. Additionally, the effects of Treg plasticity and stability on disease prognosis for several autoimmune diseases were also investigated in order to better understand the relationship between Tregs and autoimmune diseases.

Sympathetic nervous tone limits the development of myeloid-derived suppressor cells

Sympathetic nerves that innervate lymphoid organs regulate immune development and function by releasing norepinephrine that is sensed by immune cells via their expression of adrenergic receptors. Here, we demonstrate that ablation of sympathetic nervous system (SNS) signaling suppresses tumor immunity, and we dissect the mechanism of such immune suppression. We report that disruption of the SNS in mice removes a critical α-adrenergic signal required for maturation of myeloid cells in normal and tumor-bearing mice. In tumor-bearing mice, disruption of the α-adrenergic signal leads to the accumulation of immature myeloid-derived suppressor cells (MDSCs) that suppress tumor immunity and promote tumor growth. Furthermore, we show that these SNS-responsive MDSCs drive expansion of regulatory T cells via secretion of the alarmin heterodimer S100A8/A9, thereby compounding their immunosuppressive activity. Our results describe a regulatory framework in which sympathetic tone controls the development of innate and adaptive immune cells and influences their activity in health and disease.

Oridonin inhibits 4T1 tumor growth by suppressing Treg differentiation via TGF-β receptor

The Chinese herbal medicine oridonin has potent anti-inflammatory and antitumor activities. In addition, oridonin treatment effectively suppresses breast cancer growth. However, the underlying mechanisms are poorly defined. Here, we reported that oridonin decreased Treg differentiation in vitro and in vivo. Oridonin inhibition of Treg differentiation was dependent on decreasing TGF-β receptor expression. Oridonin attenuated Tregs' immunosuppressive ability; thus, oridonin did not inhibit CD8⁺ T cell proliferation very well in vitro. Oridonin greatly delayed the progression of 4T1 tumors in vivo. In addition, oridonin combined with anti-PD-1 activated a robust antitumor immune response and suppressed 4T1 tumor growth. Therefore, our results indicate that oridonin inhibits TNBC growth by modulating Treg differentiation, which provides new directions for the clinical treatment of TNBC.

P2X7 Receptor at the Crossroads of T Cell Fate

The P2X7 receptor is a ligand-gated, cation-selective channel whose main physiological ligand is ATP. P2X7 receptor activation may also be triggered by ARTC2.2-dependent ADP ribosylation in the presence of extracellular NAD. Upon activation, this receptor induces several responses, including the influx of calcium and sodium ions, phosphatidylserine externalization, the formation of a non-selective membrane pore, and ultimately cell death. P2X7 receptor activation depends on the availability of extracellular nucleotides, whose concentrations are regulated by the action of extracellular nucleotidases such as CD39 and CD38. The P2X7 receptor has been extensively studied in the context of the immune response, and it has been reported to be involved in inflammasome activation, cytokine production, and the migration of different innate immune cells in response to ATP. In adaptive immune responses, the P2X7 receptor has been linked to T cell activation, differentiation, and apoptosis induction. In this review, we will discuss the evidence of the role of the P2X7 receptor on T cell differentiation and in the control of T cell responses in inflammatory conditions.

The pivotal role of CD69 in autoimmunity

Autoimmune disorders are outcomes of impaired activity of the immune system regarding the maintenance of tolerance, which results in tissue damage secondary to an excess in the inflammatory response. Under normal conditions, the cells in the adaptive immune system are highly controlled to remain unresponsive against self-antigens (self-Ags) through various mechanisms and during different stages of maturation. CD69 (cluster of differentiation 69), a C-type lectin disulfide-linked homodimer, is expressed on different leukocytes, including newly-activated lymphocytes, certain subtypes of memory T-cells, infiltrating lymphocytes isolated from patients with chronic inflammatory disorders, and regulatory T-cells (Tregs). Cumulative evidence from in vitro and in vivo studies has revealed an immunoregulatory role for CD69. This marker has been reported to play a controversial role in chronic human inflammatory disorders. Many investigations have linked the absence of CD69 with a predisposition to inflammatory and/or autoimmune conditions, which indicates an immunoregulatory function for CD69 by mechanisms such as controlling the balance between differentiation of Th/Treg cells and enhancing the suppressive activity of Tregs. However, some reports from human studies have indicated that CD69 may exert a stimulatory effect on the inflammatory response. In this review, we first present a brief summary of the concept of 'immune tolerance' and, subsequently, review previous studies to uncover the details that underlie the immunoregulatory effects of CD69.

Inflammation Alters the Secretome and Immunomodulatory Properties of Human Skin-Derived Precursor Cells

Human skin-derived precursors (SKP) represent a group of somatic stem/precursor cells that reside in dermal skin throughout life that harbor clinical potential. SKP have a high self-renewal capacity, the ability to differentiate into multiple cell types and low immunogenicity, rendering them key candidates for allogeneic cell-based, off-the-shelf therapy. However, potential clinical application of allogeneic SKP requires that these cells retain their therapeutic properties under all circumstances and, in particular, in the presence of an inflammation state. Therefore, in this study, we investigated the impact of pro-inflammatory stimulation on the secretome and immunosuppressive properties of SKP. We demonstrated that pro-inflammatory stimulation of SKP significantly changes their expression and the secretion profile of chemo/cytokines and growth factors. Most importantly, we observed that pro-inflammatory stimulated SKP were still able to suppress the graft-versus-host response when cotransplanted with human PBMC in severe-combined immune deficient (SCID) mice, albeit to a much lesser extent than unstimulated SKP. Altogether, this study demonstrates that an inflammatory microenvironment has a significant impact on the immunological properties of SKP. These alterations need to be taken into account when developing allogeneic SKP-based therapies.

The small chain fatty acid butyrate antagonizes the TCR-stimulation-induced metabolic shift in murine epidermal gamma delta T cells

The metabolic requirements change during cell proliferation and differentiation. Upon antigen-stimulation, effector T cells switch from adenosine-triphospate (ATP)-production by oxidative phosphorylation in the mitochondria to glycolysis. In the gut it was shown that short chain fatty acids (SCFA), fermentation products of the microbiota in colon, ameliorate inflammatory reactions by supporting the differentiation of regulatory T cells. SCFA are a major energy source, but they are also anabolic metabolites, histone-deacetylase-inhibitors and activators of G protein receptors. Recently, it was reported that a topical application of the SCFA butyrate promotes regulatory T cells in the skin. Here we ask if the SCFA butyrate, propionate and acetate affect the energy metabolism and inflammatory potential of dendritic epidermal T cells (DETC), the innate resident skin γδ T cell population. Using the Seahorse™ technology, we measured glycolysis and oxidative phosphorylation (OXPHOS) in a murine DETC cell line, 7-17, upon TCR-stimulation by CD3/CD28 crosslinking, with or without SCFA addition. TCR engagement resulted in a change of the ratio glycolysis/OXPHOS. A similar metabolic shift has been described for activated CD4 T cells. Addition of 5 mM SCFA, in particular butyrate, antagonized the effect. Stimulated DETC secrete cytokines, e.g. the pro-inflammatory cytokine interferon-gamma (IFNγ), and thereby regulate skin homeostasis. Addition of butyrate and propionate to the cultures at non-toxic concentrations decreased secretion of IFNγ by DETC and increased the expression of the immunoregulatory surface receptor CD69. We hypothesize that SCFA can dampen the inflammatory activity of DETC.

CD38, a Receptor with Multifunctional Activities: From Modulatory Functions on Regulatory Cell Subsets and Extracellular Vesicles, to a Target for Therapeutic Strategies

CD38 is a multifunctional cell surface protein endowed with receptor/enzymatic functions. The protein is generally expressed at low/intermediate levels on hematological tissues and some solid tumors, scoring the highest levels on plasma cells (PC) and PC-derived neoplasia. CD38 was originally described as a receptor expressed by activated cells, mainly T lymphocytes, wherein it also regulates cell adhesion and cooperates in signal transduction mediated by major receptor complexes. Furthermore, CD38 metabolizes extracellular NAD+, generating ADPR and cyclic ADPR. This ecto-enzyme controls extra-cellular nucleotide homeostasis and intra-cellular calcium fluxes, stressing its relevance in multiple physiopathological conditions (infection, tumorigenesis and aging). In clinics, CD38 was adopted as a cell activation marker and in the diagnostic/staging of leukemias. Quantitative surface CD38 expression by multiple myeloma (MM) cells was the basic criterion used for therapeutic application of anti-CD38 monoclonal antibodies (mAbs). Anti-CD38 mAbs-mediated PC depletion in autoimmunity and organ transplants is currently under investigation. This review analyzes different aspects of CD38's role in regulatory cell populations and how these effects are obtained. Characterizing CD38 functional properties may widen the extension of therapeutic applications for anti-CD38 mAbs. The availability of therapeutic mAbs with different effects on CD38 enzymatic functions may be rapidly translated to immunotherapeutic strategies of cell immune defense.

Oxidized Low-Density Lipoprotein Receptor in Lymphocytes Prevents Atherosclerosis and Predicts Subclinical Disease

BACKGROUND

Although the role of Th17 and regulatory T cells in the progression of atherosclerosis has been highlighted in recent years, their molecular mediators remain elusive. We aimed to evaluate the association between the CD69 receptor, a regulator of Th17/regulatory T cell immunity, and atherosclerosis development in animal models and in patients with subclinical disease.

METHODS

Low-density lipoprotein receptor-deficient chimeric mice expressing or not expressing CD69 on either myeloid or lymphoid cells were subjected to a high fat diet. In vitro functional assays with human T cells were performed to decipher the mechanism of the observed phenotypes. Expression of CD69 and NR4A nuclear receptors was evaluated by reverse transcription-polymerase chain reaction in 305 male participants of the PESA study (Progression of Early Subclinical Atherosclerosis) with extensive (n=128) or focal (n=55) subclinical atherosclerosis and without disease (n=122).

RESULTS

After a high fat diet, mice lacking CD69 on lymphoid cells developed large atheroma plaque along with an increased Th17/regulatory T cell ratio in blood. Oxidized low-density lipoprotein was shown to bind specifically and functionally to CD69 on human T lymphocytes, inhibiting the development of Th17 cells through the activation of NR4A nuclear receptors. Participants of the PESA study with evidence of subclinical atherosclerosis displayed a significant CD69 and NR4A1 mRNA downregulation in peripheral blood leukocytes compared with participants without disease. The expression of CD69 remained associated with the risk of subclinical atherosclerosis in an adjusted multivariable logistic regression model (odds ratio, 0.62; 95% CI, 0.40-0.94; P=0.006) after adjustment for traditional risk factors, the expression of NR4A1, the level of oxidized low-density lipoprotein, and the counts of different leucocyte subsets.

CONCLUSIONS

CD69 depletion from the lymphoid compartment promotes a Th17/regulatory T cell imbalance and exacerbates the development of atherosclerosis. CD69 binding to oxidized low-density lipoprotein on T cells induces the expression of anti-inflammatory transcription factors. Data from a cohort of the PESA study with subclinical atherosclerosis indicate that CD69 expression in PBLs inversely correlates with the presence of disease. The expression of CD69 remained an independent predictor of subclinical atherosclerosis after adjustment for traditional risk factors.

Diammonium Glycyrrhizinate Mitigates Liver Injury Via Inhibiting Proliferation Of NKT Cells And Promoting Proliferation Of Tregs

Purpose

Diammonium glycyrrhizinate (DG) is a replacement for glycyrrhizic acid, which is used as a hepatic protector in clinical practice for most liver diseases. The potential role of immune response during autoimmune hepatitis—induced by concanavalin A (Con A)—remains to be elucidated.

Methods

C57BL/6J mice were treated with two different doses of DG (75 and 200 mg/kg) 2 hrs before administering Con A. The mice were sacrificed after administering Con A for 0, 6, and 24 hrs. Liver damage grade and serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin levels were evaluated. The expression level of cleaved-caspase 3 in liver was detected by Western blotting. Inflammatory cytokines such as tumor necrosis factor α (TNF-α), interleukin-6 (IL-6), and interferon γ (IFN-γ) in liver were detected by RT-PCR. Thymus, peripheral blood, spleen, and liver tissues were collected to analyze the percentages of NKT cells, subsets of CD4⁺CD25⁻CD69⁺ and CD8⁺CD69⁺ T cells, and subsets of regulatory T cells (Tregs).

Results

Our results revealed that DG pre-treatment significantly decreased the serum ALT and AST levels and improved the histological damage in Con A-induced autoimmune liver injury. Pre-treatment with DG down-regulated the inflammatory cytokines upon challenge with Con A. The DG pre-treatment inhibited the apoptosis of T lymphocytes in the thymus. Further, it effectively suppressed the proliferation of CD4⁺CD25⁻CD69⁺ and CD8⁺CD69⁺ subsets in the peripheral blood and spleen. In addition, the DG pretreatment significantly downregulated the frequency of NKT cells, while upregulating the frequency of Tregs in the liver.

Conclusion

We believe that the potential protective effect of DG against Con A-induced hepatitis may be partially attributed to its inhibitory activities on inflammatory cytokines in the livers, lymphocyte apoptosis in the thymus, NKT cells proliferation, and activation of CD8⁺T cells; further, there may also be a possibility of DC promoting Tregs proliferation.

CD69 Targeting Enhances Anti-vaccinia Virus Immunity

CD69 is highly expressed on the leukocyte surface upon viral infection, and its regulatory role in the vaccinia virus (VACV) immune response has been recently demonstrated using CD69^-/- mice. Here, we show augmented control of VACV infection using the anti-human CD69 monoclonal antibody (MAb) 2.8 as both preventive and therapeutic treatment for mice expressing human CD69. This control was related to increased natural killer (NK) cell reactivity and increased numbers of cytokine-producing T and NK cells in the periphery. Moreover, similarly increased immunity and protection against VACV were reproduced over both long and short periods in anti-mouse CD69 MAb 2.2-treated immunocompetent wild-type (WT) mice and immunodeficient Rag2^-/- CD69^+/+ mice. This result was not due to synergy between infection and anti-CD69 treatment since, in the absence of infection, anti-human CD69 targeting induced immune activation, which was characterized by mobilization, proliferation, and enhanced survival of immune cells as well as marked production of several innate proinflammatory cytokines by immune cells. Additionally, we showed that the rapid leukocyte effect induced by anti-CD69 MAb treatment was dependent on mTOR signaling. These properties suggest the potential of CD69-targeted therapy as an antiviral adjuvant to prevent derived infections.IMPORTANCE In this study, we demonstrate the influence of human and mouse anti-CD69 therapies on the immune response to VACV infection. We report that targeting CD69 increases the leukocyte numbers in the secondary lymphoid organs during infection and improves the capacity to clear the viral infection. Targeting CD69 increases the numbers of gamma interferon (IFN-γ)- and tumor necrosis factor alpha (TNF-α)-producing NK and T cells. In mice expressing human CD69, treatment with an anti-CD69 MAb produces increases in cytokine production, survival, and proliferation mediated in part by mTOR signaling. These results, together with the fact that we have mainly worked with a human-CD69 transgenic model, reveal CD69 as a treatment target to enhance vaccine protectiveness.

Plasmacytoid dendritic cell depletion modifies FoxP3+ T cell homeostasis and the clinical course of bacterial pneumonia in mice

Plasmacytoid dendritic cells (pDC) are critical to antiviral defense because of their high production of type I IFNs; less is known regarding their functions in bacterial infection. Moreover, pDC are involved in immunomodulation. A stable pool of regulatory T cells (Treg) is crucial for maintaining immune homeostasis. However, interactions between pDC and Treg regarding the regulation of Treg homeostasis are understudied. By using BDCA2-DTR mice as a systemic pDC depletion model, we identified increased steady-state numbers of FoxP3⁺ T cells with an effector Treg-like phenotype in lungs, liver, and spleen tissues. During sublethal, pulmonary Klebsiella pneumoniae infection, pDC deficiency also elevated respiratory FoxP3⁺ T cell numbers. Additionally, the improvement in acute pneumonia survival until day 5 post infection was accompanied by impaired proinflammatory cytokine production. In contrast, pDC-depleted mice exhibited a delayed clinical recovery during the post-acute phase. Therefore, we assume that pDC act as immunomodulators supporting the rapid onset of immune response in a proinflammatory manner and regulate inflammation or tissue regeneration in the post-acute phase. In summary, pDC assist in FoxP3⁺ T cell homeostasis and the regulation of Klebsiella-pneumonia progression.

Regulation of regulatory T cells in cancer

The inflammatory response to transformed cells forms the cornerstone of natural or therapeutically induced protective immunity to cancer. Regulatory T (Treg) cells are known for their critical role in suppressing inflammation, and therefore can antagonize effective anti-cancer immune responses. As such, Treg cells can play detrimental roles in tumour progression and in the response to both conventional and immune-based cancer therapies. Recent advances in our understanding of Treg cells reveal complex niche-specific regulatory programmes and functions, which are likely to extrapolate to cancer. The regulation of Treg cells is reliant on upstream cues from haematopoietic and non-immune cells, which dictates their genetic, epigenetic and downstream functional programmes. In this review we will discuss how Treg cells are themselves regulated in normal and transformed tissues, and the implications of this cross talk on tumour growth.

Emerging Roles of Complement Protein C1q in Neurodegeneration

The innate immune system is an ancient and primary component system that rapidly reacts to defend the body against external pathogens. C1 is the initial responder of classical pathway of the innate immune system. C1 is comprised of C1q, C1r, and C1s. Among them, C1q is known to interact with diverse ligands, which can perform various functions in physiological and pathophysiological conditions. Because C1q participates in the clearance of pathogens, its interaction with novel receptors is expected to facilitate apoptosis induction, which could prevent the onset or progression of neurodegenerative diseases and could delay the aging process. Because senescence-associated secreting phenotype determinants are generally inflammatory cytokines or immune factors to activate immune cells. In the central nervous system, C1q has diverse neuroprotective roles against pathogens and inflammation. Most of neurodegenerative diseases show region specific pathology feature in the brain. It has been suggested the evidences that the active site and amount of C1q may be disease specific. This review considers currently the emerging and under-recognized roles of C1q in neurodegeneration and highlights the need for further research to clarify these roles. Future studies on the roles of C1q in regulating disease progression should consider these aspects, including the age-dependent onset time of each neurodegenerative disease progression.

A new therapeutic target: the CD69-Myl9 system in immune responses

CD69 is an activation marker on leukocytes. Early studies showed that the CD69⁺ cells were detected in the lung of patients with asthmatic and eosinophilic pneumonia, suggesting that CD69 might play crucial roles in the pathogenesis of such inflammatory diseases, rather than simply being an activation marker. Intensive studies using mouse models have since clarified that CD69 is a functional molecule regulating the immune responses. We discovered that Myosin light chain 9, 12a, 12b (Myl9/12) are ligands for CD69 and that platelet-derived Myl9 forms a net-like structure (Myl9 nets) that is strongly detected inside blood vessels in inflamed lung. CD69-expressing activated T cells attached to the Myl9 nets can thereby migrate into the inflamed tissues through a system known as the CD69-Myl9 system. In this review, we summarize the discovery of the CD69-Myl9 system and discuss how this system is important in inflammatory immune responses. In addition, we discuss our recent finding that CD69 controls the exhaustion status of tumor-infiltrating T cells and that the blockade of the CD69 function enhances anti-tumor immunity. Finally, we discuss the possibility of CD69 as a new therapeutic target for patients with intractable inflammatory disorders and tumors.

Response kinetics reveal novel features of ageing in murine T cells

The impact of ageing on the immune system results in defects in T cell responsiveness. The search for ageing hallmarks has been challenging due to the complex nature of immune responses in which the kinetics of T cell responsiveness have largely been neglected. We aimed to unravel hallmarks of ageing in the kinetics of the murine T cell response. To this end, we assessed ageing-related T-cell response kinetics by studying the effect of the duration and strength of in vitro stimulation on activation, proliferation, and cytokine secretion by T cells of young and aged mice. Collectively, our data show that stimulatory strength and time kinetics of cytokine secretion, activation markers, and proliferation of Th, Tc, and Treg cells are crucial in understanding the impact of ageing on T cells. Despite low proliferative capacity, T cell subsets of aged mice do respond to stimulation by upregulation of activation markers and secretion of cytokines. These findings therefore indicate that replicative senescence of aged T cells is not a measure of unresponsiveness per se, but rather stress that ageing influences the kinetics of proliferation, upregulation of activation markers and cytokine secretion each to a different extent.

Risk variants disrupting enhancers of TH1 and TREG cells in type 1 diabetes

Functional interpretation of noncoding genetic variants identified by genome-wide association studies is a major challenge in human genetics and gene regulation. We generated epigenomics data using primary cells from type 1 diabetes patients. Using these data, we identified and validated multiple novel risk variants for this disease. In addition, our ranked list of candidate risk SNPs represents the most comprehensive annotation based on T1D-specific T-cell data. Because many autoimmune diseases share some genetic underpinnings, our dataset may be used to understand causal noncoding mutations in related autoimmune diseases.

Genome-wide association studies (GWASs) have revealed 59 genomic loci associated with type 1 diabetes (T1D). Functional interpretation of the SNPs located in the noncoding region of these loci remains challenging. We perform epigenomic profiling of two enhancer marks, H3K4me1 and H3K27ac, using primary T_H1 and T_REG cells isolated from healthy and T1D subjects. We uncover a large number of deregulated enhancers and altered transcriptional circuitries in both cell types of T1D patients. We identify four SNPs (rs10772119, rs10772120, rs3176792, rs883868) in linkage disequilibrium (LD) with T1D-associated GWAS lead SNPs that alter enhancer activity and expression of immune genes. Among them, rs10772119 and rs883868 disrupt the binding of retinoic acid receptor α (RARA) and Yin and Yang 1 (YY1), respectively. Loss of binding by YY1 also results in the loss of long-range enhancer–promoter interaction. These findings provide insights into how noncoding variants affect the transcriptomes of two T-cell subtypes that play critical roles in T1D pathogenesis.

Regulatory T Cells in an Endogenous Mouse Lymphoma Recognize Specific Antigen Peptides and Contribute to Immune Escape

Foxp3⁺ regulatory T cells (Tregs) sustain immune homeostasis and may contribute to immune escape in malignant disease. As a prerequisite for developing immunologic approaches in cancer therapy, it is necessary to understand the ontogeny and the antigenic specificities of tumor-infiltrating Tregs. We addressed this question by using a λ-MYC transgenic mouse model of endogenously arising B-cell lymphoma, which mirrors key features of human Burkitt lymphoma. We show that Foxp3⁺ Tregs suppress antitumor responses in endogenous lymphoma. Ablation of Foxp3⁺ Tregs significantly delayed tumor development. The ratio of Treg to effector T cells was elevated in growing tumors, which could be ascribed to differential proliferation. The Tregs detected were mainly natural Tregs that apparently recognized self-antigens. We identified MHC class II-restricted nonmutated self-epitopes, which were more prevalent in lymphoma than in normal B cells and could be recognized by Tregs. These epitopes were derived from proteins that are associated with cellular processes related to malignancy and may be overexpressed in the tumor.

CD69 enhances immunosuppressive function of regulatory T-cells and attenuates colitis by prompting IL-10 production

Foxp3⁺ regulatory T cells (Tregs) can inhibit immune responses and maintain immune tolerance by secreting immunosuppressive TGF-β1 and IL-10. However, the efficiency of Tregs become the major obstacle to their use for immunotherapy. In this study, we investigated the relevance of the C-type lectin receptor CD69 to the suppressive function. Compared to CD4⁺Foxp3⁺CD69⁻ Tregs (CD69⁻ Tregs), CD4⁺Foxp3⁺CD69⁺ Tregs (CD69⁺ Tregs) displayed stronger ability to maintain immune tolerance. CD69⁺ Tregs expressed higher levels of suppression-associated markers such as CTLA-4, ICOS, CD38 and GITR, and secreted higher levels of IL-10 but not TGF-β1. CD69⁺ Tregs from Il10^+/+ rather than Il10^−/− mice significantly inhibit the proliferation of CD4⁺ T cells. CD69 over-expression stimulated higher levels of IL-10 and c-Maf expression, which was compromised by silencing of STAT3 or STAT5. In addition, the direct interaction of STAT3 with the c-Maf promoter was detected in cells with CD69 over-expression. Moreover, adoptive transfer of CD69⁺ Tregs but not CD69⁻Tregs or CD69⁺ Tregs deficient in IL-10 dramatically prevented the development of inflammatory bowel disease (IBD) in mice. Taken together, CD69 is important to the suppressive function of Tregs by promoting IL-10 production. CD69⁺ Tregs have the potential to develop new therapeutic approach for autoimmune diseases like IBD.

Immunological Properties of Human Embryonic Stem Cell-Derived Retinal Pigment Epithelial Cells

Age-related macular degeneration is caused by dysfunction and loss of retinal pigment epithelium (RPE) cells, and their transplantation may rescue visual functions and delay disease progression. Human embryonic stem cells (hESCs) may be an unlimited source of RPE cells for allotransplantation. We analyzed the immunomodulatory properties of hESC-derived RPE (hESC-RPE) cells, and showed that they inhibited T cell responses. Co-culture experiments showed that RPE cells inhibited interfon-γ secretion and proliferation of activated T cells. Furthermore, hESC-RPE cells enhanced T cell apoptosis and secretion of the anti-inflammatory cytokine interleukin-10 (IL-10). In addition, RPE cells altered the expression of T cell activation markers, CD69 and CD25. RPE cells transplanted into RCS rats without immunosuppression survived, provided retinal rescue, and enhanced IL-10 blood levels. Our data suggest that hESC-RPE cells have immunosuppressive properties. Further studies will determine if these properties are sufficient to alleviate the need for immunosuppression therapy after their clinical allotransplantation.

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T cells proliferation and IFN-γ secretion are inhibited by hESC-RPE cells

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T cells apoptosis and secretion of IL-10 are enhanced by hESC-RPE cells

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RPE cells survive, provide retinal rescue, and enhance IL-10 blood levels in vivo

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These findings are relevant to immunosuppressive regimens for RPE cell therapies

NAT2 Gene Polymorphisms in Turkish Patients with Psoriasis Vulgaris

Psoriasis is a common, chronic, and autoimmune skin disease. Factors that play a role in etiopathogenesis of psoriasis include internal factors such as genetic susceptibility and immunological factors and external factors such as stress, infection, trauma, drug, and environmental compounds. N-acetyltransferase 2 (NAT2) is a xenobiotic enzyme that is involved in the metabolism of drugs, environmental toxins, and carcinogens. In this study, we aimed to demonstrate whether the variations in the NAT2 gene lead to a predisposition to psoriasis by affecting the enzyme's ability to metabolize drugs and environmental components or not. Three polymorphisms (rs1799929, rs1799930, and rs1799931) in NAT2 gene were genotyped and compared by real-time PCR method in 260 psoriasis vulgaris patients and 200 healthy controls. There was no difference in the genotype distributions and allele frequencies of polymorphisms between psoriasis vulgaris patients and controls. When the effects of polymorphisms on the clinical features of the disease, such as onset age and severity, are assessed, it has been found that rs1799930 and rs1799929 are, respectively, associated with early onset age and severity of the disease. In conclusion, rs1799929, rs1799930, and rs1799931 polymorphisms of the NAT-2 gene do not appear to be a risk factor for the development of psoriasis. Conversely, they may have an effect on either more severe or early onset cases of the disease.

Spatial distribution and function of T follicular regulatory cells in human lymph nodes

T follicular regulatory (Tfr) cells are a population of CD4⁺ T cells that express regulatory T cell markers and have been shown to suppress humoral immunity. However, the precise mechanisms and location of Tfr-mediated suppression in the lymph node (LN) microenvironment are unknown. Using highly multiplexed quantitative imaging and functional assays, we examined the spatial distribution, suppressive function, and preferred interacting partners of Tfr cells in human mesenteric LNs. We find that the majority of Tfr cells express low levels of PD-1 and reside at the border between the T cell zone and B cell follicle, with very few found in the germinal centers (GCs). Although PD-1⁺ Tfr cells expressed higher levels of CD38, CTLA-4, and GARP than PD-1^Neg Tfr cells, both potently suppressed antibody production in vitro. These findings highlight the phenotypic diversity of human Tfr cells and suggest that Tfr-mediated suppression is most efficient at the T-B border and within the follicle, not in the GC.

Crucial role for CD69 in allergic inflammatory responses: CD69-Myl9 system in the pathogenesis of airway inflammation

CD69 has been known as an early activation marker of lymphocytes; whereas, recent studies demonstrate that CD69 also has critical functions in immune responses. Early studies using human samples revealed the involvement of CD69 in various inflammatory diseases including asthma. Moreover, murine disease models using Cd69^-/- mice and/or anti-CD69 antibody (Ab) treatment have revealed crucial roles for CD69 in inflammatory responses. However, it had not been clear how the CD69 molecule contributes to the pathogenesis of inflammatory diseases. We recently elucidated a novel mechanism, in which the interaction between CD69 and its ligands, myosin light chain 9, 12a and 12b (Myl9/12) play a critical role in the recruitment of activated T cells into the inflammatory lung. In this review, we first summarize CD69 function based on its structure and then introduce the evidence for the involvement of CD69 in human diseases and murine disease models. Then, we will describe how we discovered CD69 ligands, Myl9 and Myl12, and how the CD69-Myl9 system regulates airway inflammation. Finally, we will discuss possible therapeutic usages of the blocking Ab to the CD69-Myl9 system.

CD69: from activation marker to metabolic gatekeeper

CD69 is a membrane-bound, type II C-lectin receptor. It is a classical early marker of lymphocyte activation due to its rapid appearance on the surface of the plasma membrane after stimulation. CD69 is expressed by several subsets of tissue resident immune cells, including resident memory T (TRM) cells and gamma delta (γδ) T cells, and is therefore considered a marker of tissue retention. Recent evidence has revealed that CD69 regulates some specific functions of selected T-cell subsets, determining the migration-retention ratio as well as the acquisition of effector or regulatory phenotypes. Specifically, CD69 regulates the differentiation of regulatory T (Treg) cells as well as the secretion of IFN-γ, IL-17, and IL-22. The identification of putative CD69 ligands, such as Galectin-1 (Gal-1), suggests that CD69-induced signaling can be regulated not only during cognate contacts between T cells and antigen-presenting cells in lymphoid organs, but also in the periphery, where cytokines and other metabolites control the final outcome of the immune response. Here, we will discuss new aspects of the molecular signaling mediated by CD69 and its involvement in the metabolic reprogramming regulating TH-effector lineages.

Distinctive Surface Glycosylation Patterns Associated With Mouse and Human CD4+ Regulatory T Cells and Their Suppressive Function

Regulatory T-cells (Treg) are essential for maintaining immune homeostasis and tolerance. Surface glycosylation is ubiquitous on mammalian cells and regulates diverse biological processes. While it is currently well accepted that surface glycan expression influences multiple aspects of T-cell function, little is known about the relevance of glycosylation to Treg biology. This study aimed to profile the surface glycosylation characteristics of Treg in various lymphoid compartments of mouse and in human peripheral blood with comparison to non-regulatory, conventional CD4⁺ T-cells (Tconv). It also sought to determine the relationship between the surface glycosylation characteristics and suppressive potency of Treg. Lectin-based flow cytometric profiling demonstrated that Treg surface glycosylation differs significantly from that of Tconv in the resting state and is further modified by activation stimuli. In mouse, the surface glycosylation profiles of FoxP3⁺ Treg from spleen and lymph nodes were closely comparable but greater variability was observed for Treg in thymus, bone marrow, and blood. Surface levels of tri/tetra-antennary N-glycans correlated with expression of proteins known to be involved in Treg suppressive functions, including GITR, PD-1, PD-L1, CD73, CTLA-4, and ICOS. In coculture experiments involving purified Treg subpopulations and CD4⁺ or CD8⁺ Tconv, higher surface tri/tetra-antennary N-glycans was associated with greater Treg suppressive potency. Enzymatic manipulation of mouse Treg surface glycosylation resulting in a temporary reduction of surface N-glycans significantly reduced Treg capacity to suppress Tconv activation through contact-dependent mechanisms. Overall, these findings demonstrate that Treg have distinctive surface glycan characteristics that show variability across anatomical locations and are modulated by activation events. They also provide evidence of an important role for surface glycosylation in determining Treg phenotype and suppressive potency. These insights may prove relevant to the analysis of Treg in disease settings and to the further development of Treg-based immunotherapies.

Sexual Dimorphic Responses in Lymphocytes of Healthy Individuals after Carica papaya Consumption

Sexual dimorphism in immune response is widely recognized, but few human studies have observed this distinction. Food with endo-immunomodulatory potential may reveal novel sex-biased in vivo interactions. Immunomodulatory effects of Carica papaya were compared between healthy male and female individuals. Volunteers were given fixed meals supplemented with papaya for 2 days. Changes in blood immune profiles and hormone levels were determined. In females, total natural killer (NK) cell percentages decreased (12.7 ± 4.4 vs 14.6 ± 5.8%, p = 0.018, n = 18) while B cells increased (15.2 ± 5.5 vs 14.5 ± 5.0, p = 0.037, n = 18) after papaya consumption. Increased 17β-estradiol (511.1 ± 579.7 vs 282.7 ± 165.0 pmol/l, p = 0.036, n = 9) observed in females may be crucial to this change. Differentiation markers (CD45RA, CD69, CD25) analyzed on lymphocytes showed naïve (CD45RA⁺) non-CD4⁺ lymphocytes were reduced in females (40.7 ± 8.1 vs 46.8 ± 5.4%, p = 0.012, n = 8) but not males. A general suppressive effect of papaya on CD69⁺ cells, and higher percentage of CD69⁺ populations in females and non-CD4 lymphocytes, may be relevant. CD107a⁺ NK cells were significantly increased in males (16.8 ± 7.0 vs 14.7 ± 4.8, p = 0.038, n = 9) but not females. Effect in females may be disrupted by the action of progesterone, which was significantly correlated with this population (R = 0.771, p = 0.025, n = 8) after papaya consumption. In males, total T helper cells were increased (33.4 ± 6.4 vs 32.4 ± 6.1%, p = 0.040, n = 15). Strong significant negative correlation between testosterone and CD25⁺CD4⁺ lymphocytes, may play a role in the lower total CD4⁺ T cells reported in males. Thus, dissimilar immune profiles were elicited in the sexes after papaya consumption and may have sex hormone influence.

Thymus-Derived Regulatory T Cell Development Is Regulated by C-Type Lectin-Mediated BIC/MicroRNA 155 Expression

Thymus-derived regulatory T (tTreg) cells are key to preventing autoimmune diseases, but the mechanisms involved in their development remain unsolved. Here, we show that the C-type lectin receptor CD69 controls tTreg cell development and peripheral Treg cell homeostasis through the regulation of BIC/microRNA 155 (miR-155) and its target, suppressor of cytokine signaling 1 (SOCS-1). Using Foxp3-mRFP/cd69^+/- or Foxp3-mRFP/cd69^-/- reporter mice and short hairpin RNA (shRNA)-mediated silencing and miR-155 transfection approaches, we found that CD69 deficiency impaired the signal transducer and activator of transcription 5 (STAT5) pathway in Foxp3⁺ cells. This results in BIC/miR-155 inhibition, increased SOCS-1 expression, and severely impaired tTreg cell development in embryos, adults, and Rag2^-/- γc^-/- hematopoietic chimeras reconstituted with cd69^-/- stem cells. Accordingly, mirn155^-/- mice have an impaired development of CD69⁺ tTreg cells and overexpression of the miR-155-induced CD69 pathway, suggesting that both molecules might be concomitantly activated in a positive-feedback loop. Moreover, in vitro-inducible CD25⁺ Treg (iTreg) cell development is inhibited in Il2rγ^-/-/cd69^-/- mice. Our data highlight the contribution of CD69 as a nonredundant key regulator of BIC/miR-155-dependent Treg cell development and homeostasis.