CD3 expression distinguishes two gammadeltaT cell receptor subsets with different phenotype and effector function in tuberculous pleurisy

Invariant γδTCR natural killer-like effector T cells in the naked mole-rat

The naked mole-rat (Heterocephalus glaber) is a long-lived rodent species showing resistance to the development of cancer. Although naked mole-rats have been reported to lack natural killer (NK) cells, γδ T cell-based immunity has been suggested in this species, which could represent an important arm of the immune system for antitumor responses. Here, we investigate the biology of these unconventional T cells in peripheral tissues (blood, spleen) and thymus of the naked mole-rat at different ages by TCR repertoire profiling and single-cell gene expression analysis. Using our own TCR annotation in the naked mole-rat genome, we report that the γδ TCR repertoire is dominated by a public invariant Vγ4-2/Vδ1-4 TCR, containing the complementary-determining-region-3 (CDR3)γ CTYWDSNYAKKLF / CDR3δ CALWELRTGGITAQLVF that are likely generated by short-homology-repeat-driven DNA rearrangements. This invariant TCR is specifically found in γδ T cells expressing genes associated with NK cytotoxicity and is generated in both the thoracic and cervical thymus of the naked mole-rat until adult life. Our results indicate that invariant Vγ4-2/Vδ1-4 NK-like effector T cells in the naked mole-rat can contribute to tumor immunosurveillance by γδ TCR-mediated recognition of a common molecular signal.

Double-negative T cells ameliorate psoriasis by selectively inhibiting IL-17A-producing γδlow T cells

BACKGROUND

Psoriasis is a chronic immune-mediated skin condition. Although biologic treatments are effective in controlling psoriasis, some patients do not respond or lose response to these therapies. Thus, new strategies for psoriasis treatment are still urgently needed. Double-negative T cells (DNT) play a significant immunoregulatory role in autoimmune diseases. In this study, we aimed to evaluate the protective effect of DNT in psoriasis and explore the underlying mechanism.

METHODS

We conducted a single adoptive transfer of DNT into an imiquimod (IMQ)-induced psoriasis mouse model through tail vein injection. The skin inflammation and IL-17A producing γδ T cells were evaluated.

RESULTS

DNT administration significantly reduced the inflammatory response in mouse skin, characterized by decreased skin folds, scales, and red patches. After DNT treatment, the secretion of IL-17A by RORc+ γδlow T cells in the skin was selectively suppressed, resulting in an amelioration of skin inflammation. Transcriptomic data suggested heightened expression of NKG2D ligands in γδlow T cells within the mouse model of psoriasis induced by IMQ. When blocking the NKG2D ligand and NKG2D (expressed by DNT) interaction, the cytotoxic efficacy of DNT against RORc+IL17A+ γδlow T cells was attenuated. Using Ccr5-/- DNT for treatment yielded evidence that DNT migrates into inflamed skin tissue and fails to protect IMQ-induced skin lesions.

CONCLUSIONS

DNT could migrate to inflamed skin tissue through CCR5, selectively inhibit IL-17-producing γδlow T cells and finally ameliorate mouse psoriasis. Our study provides feasibility for using immune cell therapy for the prevention and treatment of psoriasis in the clinic.

Inhibition of Mitochondrial Translation Ameliorates Imiquimod-Induced Psoriasis-Like Skin Inflammation by Targeting Vγ4+ γδ T Cells

Psoriasis is an inflammatory skin disorder that is characterized by keratinocyte hyperproliferation in response to immune cell infiltration and cytokine secretion in the dermis. γδ T cells expressing the Vγ4 TCR chain are among the highest contributors of IL-17A, which is a major cytokine that drives a psoriasis flare, making Vγ4+ γδ T cells a suitable target to restrict psoriasis progression. In this study, we demonstrate that mitochondrial translation inhibition within Vγ4+ γδ T cells effectively reduced erythema, scaling, and skin thickening in a murine model of psoriatic disease. The antibiotic linezolid, which blocks mitochondrial translation, inhibited the production of mitochondrial-encoded protein cytochrome c oxidase in Vγ4+ γδ T cells and systemically reduced the frequencies of IL-17A+ Vγ4+ γδ T cells, effectively resolving IL-17A-dependent inflammation. Inhibiting mitochondrial translation could be a novel metabolic approach to interrupt IL-17A signaling in Vγ4+ T cells and reduce psoriasis-like skin pathophysiology.

Exploring modulations in T-cell receptor-mediated T-cell signaling events in systemic circulation and at local disease site of patients with tubercular pleural effusion: An attempt to understand tuberculosis pathogenesis at the local disease site

Introduction

T cells are crucial for pathogenesis as well as control for tuberculosis (TB). Although much is known about the signaling pathways which are required for the activation of T cells during acute infection but the way these cells respond during persistent of infection still remained elusive. Therefore, it is rationale to understand T cell activation during tuberculous pleural effusion (TPE), which is similar to bacterial persistency system.

Methods

Herein, we will employ T cell receptor (TCR) based approaches for studying events of T cell activation pathways in cells of blood and pleural fluid among patients with TPE. We performed spectrofluorimetric analysis to study effect of M. tuberculosis antigens, ESAT-6 and Ag85A stimulation on intracellular calcium levels, Phosphorylation levels of ZAP-70 (Zeta-chain-associated protein kinase 70), PKC-θ (Protein kinase C theta), Erk1/2 (Extracellular signal-regulated kinase 1 and 2) and p-38 two important members of MAPKs (Mitogen activated Protein kinases) in CD3 and CD28 induced cells of blood and pleural fluid of same patients with TPE by western blotting. Patients with non-TPE were also included as matching disease controls in this study.

Results

We observed significantly higher intracellular calcium levels, Phosphorylation levels of ZAP-70, Erk1/2 and p-38 in CD3 and CD28 induced cells of pleural fluid as compared to the blood cells of same patients with TPE. Alteration in the activation of these events has also been noted after stimulation of ESAT-6 and Ag85A.

Discussion

Present study demonstrated up-regulated activation of TCR mediated T cell signaling events at local disease site (Pleural fluid) as compared to the blood sample of TB pleurisy patients which could be involved in T-cell dysfunctioning during the progression of the disease and also could be responsible for Th 1 dominance at local disease site in patients with TPE.

Reciprocal alterations in circulating and hepatic gamma-delta T cells in patients with primary biliary cholangitis

BACKGROUND AND AIMS

Gamma-delta (γδ) T cells are involved in the development of diverse liver and autoimmune diseases, whereas the role of γδ T cells in primary biliary cholangitis (PBC) remains unclear.

METHODS

We analyzed the number, phenotypes, and functional molecules of both circulating and hepatic γδ T cells in PBC patients and healthy controls (HCs) by flow cytometric analysis and immunohistochemistry.

RESULTS

We identified two distinct functional subsets of circulating γδ T cells according to the CD3/TCRγδ complex: the TCRγδ^high and TCRγδ^low subsets. Approximately, three-quarters of cells in the TCRγδ^high subset were Vδ1 T cells, while Vδ2 T cells were enriched in the TCRγδ^low subset in HCs. The frequency and absolute number of circulating TCRγδ^low cells were significantly decreased in PBC patients compared with HCs (p < 0.001). Furthermore, the frequency of TCRγδ^low cells was correlated with disease severity and ursodeoxycholic acid (UDCA) response. TCRγδ^low cells exhibited a similar apoptotic and proliferative phenotype, but enhanced liver-homing chemokine receptor (CXCR6) expression in PBC patients compared with HCs. In addition, circulating TCRγδ^low cells were more activated and produced higher granzyme B (GZMB) in PBC patients compared with HCs. Finally, compared with heathy liver controls, hepatic γδ T cells were increased and infiltrated in the inflamed portal tracts in PBC liver. Furthermore, the number of hepatic γδ T cells was correlated with cholestatic markers and UDCA response.

CONCLUSION

The circulating TCRγδ^low subset may migrate to the liver via the CXCR6-CXCL16 axis and be involved in the pathogenesis of PBC by increasing GZMB production.

Suppressive activity of Vδ2+ γδ T cells on αβ T cells is licensed by TCR signaling and correlates with signal strength

Despite recent progress in the understanding of γδ T cells' roles and functions, their interaction with αβ T cells still remains to be elucidated. In this study, we sought to clarify what precisely endows peripheral Vδ2+ T cells with immunosuppressive function on autologous αβ T cells. We found that negatively freshly isolated Vδ2+ T cells do not exhibit suppressive behavior, even after stimulation with IL-12/IL-18/IL-15 or the sheer contact with butyrophilin-3A1-expressing tumor cell lines (U251 or SK-Mel-28). On the other hand, Vδ2+ T cells positively isolated through TCR crosslinking or after prolonged stimulation with isopentenyl pyrophosphate (IPP) mediate strong inhibitory effects on αβ T cell proliferation. Stimulation with IPP in the presence of IL-15 induces the most robust suppressive phenotype of Vδ2+ T cells. This indicates that Vδ2+ T cells' suppressive activity is dependent on a TCR signal and that the degree of suppression correlates with its strength. Vδ2+ T cell immunosuppression does not correlate with their Foxp3 expression but rather with their PD-L1 protein expression, evidenced by the massive reduction of suppressive activity when using a blocking antibody. In conclusion, pharmacologic stimulation of Vδ2+ T cells via the Vδ2 TCR for activation and expansion induces Vδ2+ T cells' potent killer activity while simultaneously licensing them to suppress αβ T cell responses. Taken together, the study is a further step to understand-in more detail-the suppressive activity of Vδ2+ γδ T cells.

Human γδ T-cell receptor repertoire is shaped by influenza viruses, age and tissue compartmentalisation

Background

Although γδ T cells comprise up to 10% of human peripheral blood T cells, questions remain regarding their role in disease states and T‐cell receptor (TCR) clonal expansions. We dissected anti‐viral functions of human γδ T cells towards influenza viruses and defined influenza‐reactive γδ TCRs in the context of γδ‐TCRs across the human lifespan.

Methods

We performed ⁵¹Cr‐killing assay and single‐cell time‐lapse live video microscopy to define mechanisms underlying γδ T‐cell‐mediated killing of influenza‐infected targets. We assessed cytotoxic profiles of γδ T cells in influenza‐infected patients and IFN‐γ production towards influenza‐infected lung epithelial cells. Using single‐cell RT‐PCR, we characterised paired TCRγδ clonotypes for influenza‐reactive γδ T cells in comparison with TCRs from healthy neonates, adults, elderly donors and tissues.

Results

We provide the first visual evidence of γδ T‐cell‐mediated killing of influenza‐infected targets and show distinct features to those reported for CD8⁺ T cells. γδ T cells displayed poly‐cytotoxic profiles in influenza‐infected patients and produced IFN‐γ towards influenza‐infected cells. These IFN‐γ‐producing γδ T cells were skewed towards the γ9δ2 TCRs, particularly expressing the public GV9‐TCRγ, capable of pairing with numerous TCR‐δ chains, suggesting their significant role in γδ T‐cell immunity. Neonatal γδ T cells displayed extensive non‐overlapping TCRγδ repertoires, while adults had enriched γ9δ2‐pairings with diverse CDR3γδ regions. Conversely, the elderly showed distinct γδ‐pairings characterised by large clonal expansions, a profile also prominent in adult tissues.

Conclusion

Human TCRγδ repertoire is shaped by age, tissue compartmentalisation and the individual's history of infection, suggesting that these somewhat enigmatic γδ T cells indeed respond to antigen challenge.

CD3ε Expression Defines Functionally Distinct Subsets of Vδ1 T Cells in Patients With Human Immunodeficiency Virus Infection

Human γδ T cells expressing the Vδ1 T cell receptor (TCR) recognize self and microbial antigens and stress-inducible molecules in a major histocompatibility complex-unrestricted manner and are an important source of innate interleukin (IL)-17. Vδ1 T cells are expanded in the circulation and intestines of patients with human immunodeficiency virus (HIV) infection. In this study, we show that patients with HIV have elevated frequencies, but not absolute numbers, of circulating Vδ1 T cells compared to control subjects. This increase was most striking in the patients with Candida albicans co-infection. Using flow cytometry and confocal microscopy, we identify two populations of Vδ1 T cells, based on low and high expression of the ε chain of the CD3 protein complex responsible for transducing TCR-mediated signals (denoted CD3ε^lo and CD3ε^hi Vδ1 T cells). Both Vδ1 T cell populations expressed the CD3 ζ-chain, also used for TCR signaling. Using lines of Vδ1 T cells generated from healthy donors, we show that CD3ε can be transiently downregulated by activation but that its expression is restored over time in culture in the presence of exogenous IL-2. Compared to CD3ε^hi Vδ1 T cells, CD3ε^lo Vδ1 T cells more frequently expressed terminally differentiated phenotypes and the negative regulator of T cell activation, programmed death-1 (PD-1), but not lymphocyte-activation gene 3, and upon stimulation in vitro, only the CD3ε^hi subset of Vδ1 T cells, produced IL-17. Thus, while HIV can infect and kill IL-17-producing CD4⁺ T cells, Vδ1 T cells are another source of IL-17, but many of them exist in a state of exhaustion, mediated either by the induction of PD-1 or by downregulation of CD3ε expression.

ORAI1 mutations abolishing store-operated Ca2+ entry cause anhidrotic ectodermal dysplasia with immunodeficiency

BACKGROUND

Store-operated Ca²⁺ entry (SOCE) through Ca²⁺ release-activated Ca²⁺ channels is an essential signaling pathway in many cell types. Ca²⁺ release-activated Ca²⁺ channels are formed by ORAI1, ORAI2, and ORAI3 proteins and activated by stromal interaction molecule (STIM) 1 and STIM2. Mutations in the ORAI1 and STIM1 genes that abolish SOCE cause a combined immunodeficiency (CID) syndrome that is accompanied by autoimmunity and nonimmunologic symptoms.

OBJECTIVE

We performed molecular and immunologic analysis of patients with CID, anhidrosis, and ectodermal dysplasia of unknown etiology.

METHODS

We performed DNA sequencing of the ORAI1 gene, modeling of mutations on ORAI1 crystal structure, analysis of ORAI1 mRNA and protein expression, SOCE measurements, immunologic analysis of peripheral blood lymphocyte populations by using flow cytometry, and histologic and ultrastructural analysis of patient tissues.

RESULTS

We identified 3 novel autosomal recessive mutations in ORAI1 in unrelated kindreds with CID, autoimmunity, ectodermal dysplasia with anhidrosis, and muscular dysplasia. The patients were homozygous for p.V181SfsX8, p.L194P, and p.G98R mutations in the ORAI1 gene that suppressed ORAI1 protein expression and SOCE in the patients' lymphocytes and fibroblasts. In addition to impaired T-cell cytokine production, ORAI1 mutations were associated with strongly reduced numbers of invariant natural killer T and regulatory T (Treg) cells and altered composition of γδ T-cell and natural killer cell subsets.

CONCLUSION

ORAI1 null mutations are associated with reduced numbers of invariant natural killer T and Treg cells that likely contribute to the patients' immunodeficiency and autoimmunity. ORAI1-deficient patients have dental enamel defects and anhidrosis, representing a new form of anhidrotic ectodermal dysplasia with immunodeficiency that is distinct from previously reported patients with anhidrotic ectodermal dysplasia with immunodeficiency caused by mutations in the nuclear factor κB signaling pathway (IKBKG and NFKBIA).

High Interferon-γ Uniquely in Vδ1 T Cells Correlates with Markers of Inflammation and Axonal Damage in Early Multiple Sclerosis

We have identified a population of T lymphocytes in peripheral blood, Vδ1 TCRγδ T lymphocytes, which unexpectedly was uniquely expressing high production of interferon-γ in newly diagnosed, untreated multiple sclerosis (MS) patients. IFN-γ production in this population distinctly correlated to parameters of clinical disease activity, inflammation, and neuronal damage. These Vδ1 T lymphocytes belong to a population of innate T lymphocytes that recognize antigen in the context of CD1d/CD1c and which include reactivity to the myelin glycosphingolipid sulfatide. Importantly, patients treated with natalizumab, blocking leukocyte transmigration to central nervous system, had completely normalized levels of interferon-γ-producing Vδ1 T lymphocytes. A biomarker and early sign of demyelinating disease in MS is much warranted and would help identify immunopathogenesis and prognosis of disease as well as monitor success with adequate treatment. The present study identifies the Vδ1 T lymphocytes as an early marker of MS and a possible link to understanding the disease etiology.

CD3bright signals on γδ T cells identify IL-17A-producing Vγ6Vδ1+ T cells

Interleukin-17A (IL-17A) is a pro-inflammatory cytokine that has an important role at mucosal sites in a wide range of immune responses including infection, allergy and auto-immunity. γδ T cells are recognized as IL-17 producers, but based on the level of CD3 expression, we now define the remarkable ability of a CD3(bright) γδ T-cell subset with an effector memory phenotype to rapidly produce IL-17A, but not interferon-γ. CD3(bright) γδ T cells uniformly express the canonical germline encoded Vγ6/Vδ1(+) T-cell receptor. They are widely distributed with a preferential representation in the lungs and skin are negatively impacted in the absence of retinoic acid receptor-related orphan receptor gammat expression or endogenous flora. This population responded rapidly to various stimuli in a mechanism involving IL-23 and NOD-like receptor family, pyrin domain containing 3 (NLRP3)-inflammasome-dependent IL-1β. Finally, we demonstrated that IL-17-producing CD3(bright) γδ T cells responded promptly and strongly to pneumococcal infection and during skin inflammation. Here, we propose a new way to specifically analyze IL-17-producing Vγ6/Vδ1(+) T cells based on the level of CD3 signals. Using this gating strategy, our data reinforce the crucial role of this γδ T-cell subset in respiratory and skin disorders.

Microbe-specific unconventional T cells induce human neutrophil differentiation into antigen cross-presenting cells

The early immune response to microbes is dominated by the recruitment of neutrophils whose primary function is to clear invading pathogens. However, there is emerging evidence that neutrophils play additional effector and regulatory roles. The present study demonstrates that human neutrophils assume Ag cross-presenting functions and suggests a plausible scenario for the local generation of APC-like neutrophils through the mobilization of unconventional T cells in response to microbial metabolites. Vγ9/Vδ2 T cells and mucosal-associated invariant T cells are abundant in blood, inflamed tissues, and mucosal barriers. In this study, both human cell types responded rapidly to neutrophils after phagocytosis of Gram-positive and Gram-negative bacteria producing the corresponding ligands, and in turn mediated the differentiation of neutrophils into APCs for both CD4(+) and CD8(+) T cells through secretion of GM-CSF, IFN-γ, and TNF-α. In patients with acute sepsis, circulating neutrophils displayed a similar APC-like phenotype and readily processed soluble proteins for cross-presentation of antigenic peptides to CD8(+) T cells, at a time when peripheral Vγ9/Vδ2 T cells were highly activated. Our findings indicate that unconventional T cells represent key controllers of neutrophil-driven innate and adaptive responses to a broad range of pathogens.

Human pleural B-cells regulate IFN-γ production by local T-cells and NK cells in a Mycobacterium tuberculosis-induced delayed hypersensitivity reaction

DTH (delayed type hypersensitivity) reactions are secondary cellular immune responses that appear 24-72 h after antigen exposure. Tuberculous pleurisy is a common manifestation of extrapulmonary TB (tuberculosis) and is considered a human model of Th1-mediated DTH. In order to identify functional cross-talk among cellular populations sited in this inflammatory microenvironment, we analysed phenotypic and functional features of human B-cells isolated from the PF (pleural fluid) of TB patients. Freshly isolated PF-B-cells displayed a lower expression of CD20, CD1d and HLA-DR, and a higher expression of CD95, CD38, CD25, CXCR3 (CXC chemokine receptor 3) and CXCR4 (CXC chemokine receptor 4) than their PB (peripheral blood) counterparts, suggesting a non-classical in situ activation. Although memory PF-T-cell frequencies were increased, the frequencies of memory PF-B-cells were not. We demonstrated that, upon stimulation with γ-irradiated M. tuberculosis, mycobacterially secreted proteins or a lectin mitogen, PF-B-cells had a strong activation and produced IL-10 by a mechanism that was dependent on bystander activation of CD19(-) PF cells. Besides, within PF cells, B-cells diminished in vitro M. tuberculosis-induced IFN (interferon)-γ production by T-cells and NK (natural killer) cells in an IL-10-dependent manner. Finally, we found that the lower the frequency of B-cells, the higher the ratio of IFN-γ/IL-10 within PF. Thus our results suggest that B-cells can regulate a human DTH reaction induced by M. tuberculosis.

Nonclassical T cells and their antigens in tuberculosis

T cells that recognize nonpeptidic antigens, and thereby are identified as nonclassical, represent important yet poorly characterized effectors of the immune response. They are present in large numbers in circulating blood and tissues and are as abundant as T cells recognizing peptide antigens. Nonclassical T cells exert multiple functions including immunoregulation, tumor control, and protection against infections. They recognize complexes of nonpeptidic antigens such as lipid and glycolipid molecules, vitamin B2 precursors, and phosphorylated metabolites of the mevalonate pathway. Each of these antigens is presented by antigen-presenting molecules other than major histocompatibility complex (MHC), including CD1, MHC class I-related molecule 1 (MR1), and butyrophilin 3A1 (BTN3A1) molecules. Here, we discuss how nonclassical T cells participate in the recognition of mycobacterial antigens and in the mycobacterial-specific immune response.

Levels of inflammatory cytokines, adrenal steroids, and mRNA for GRα, GRβ and 11βHSD1 in TB pleurisy

Our previous work on the immune-endocrine features of patients with pulmonary tuberculosis (TB) showed markedly decreased plasma levels of dehydroepiandrosterone (DHEA) together with augmented concentrations of Cortisol and pro- and anti-inflammatory cytokines. Studies in peripheral blood mononuclear cells (PBMC) indicated a lower mRNA α/β ratio of glucocorticoid receptors -GR- together with a higher 11β-hydroxysteroid dehydrogenase type 1 (11βHSD1) mRNA expression in cases with severe pulmonary TB. Since Pleural TB (PLTB) is a rather benign manifestation of TB, we now analyzed the systemic and local immune-endocrine profile as well as the GRα, GRβ, 11βHSD1 and 11βHSD2 transcripts in PBMC and pleural effusion mononuclear cells (PEMC) of patients with PLTB. PLTB patients had increased levels of IL-1β, IL-6 and IFNγ together with reduced Cortisol and DHEA concentrations in pleural fluids. Also, a significantly increased expression of 11βHSD1 and GRα was found in PEMC compared to PBMC. Findings point out to an appropriate immune response and a substantial inflammatory reaction, wherein the low Cortisol concentrations may be equally effective, because of the increased expression of GRα and 11βHSD1 transcripts which may optimize the immunomodulatory properties of Cortisol.

An abnormal phenotype of lung Vγ9Vδ2 T cells impairs their responsiveness in tuberculosis patients

Antigen-specific γδ T cells represent an early innate defense known to play an important role in anti-mycobacterial immunity. We have investigated the immune functions of Vγ9Vδ2 T cells from Broncho-Alveolar lavages (BAC) samples of active TB patients. We observed that BAC Vγ9Vδ2 T cells presented a strong down-modulation of CD3 expression compared with Vγ9Vδ2 T cells from peripheral blood. Furthermore, Vγ9Vδ2 T cells mainly showed a central memory phenotype, expressed high levels of NK inhibitory receptors and TEMRA cells showed low expression of CD16 compared to circulating Vγ9Vδ2 T cells. Interestingly, the ability of BAC Vγ9Vδ2 T cells to respond to antigen stimulation was dramatically reduced, differently from blood counterpart. These observations indicate that γδ T cell functions are specifically impaired in situ by active TB, suggesting that the alveolar ambient during tuberculosis may affect resident γδ T cells in comparison to circulating cells.