Subset Of Γδ Research Articles

The molecular mechanisms supporting the homeostasis and activation of dendritic epidermal T cell and its role in promoting wound healing.

The epidermis is the outermost layer of skin and the first barrier against invasion. Dendritic epidermal T cells (DETCs) are a subset of γδ T cells and an important component of the epidermal immune microenvironment. DETCs are involved in skin wound healing, malignancy and autoimmune diseases. DETCs secrete insulin-like growth factor-1 and keratinocyte growth factor for skin homeostasis and re-epithelization and release inflammatory factors to adjust the inflammatory microenvironment of wound healing. Therefore, an understanding of their development, activation and correlative signalling pathways is indispensable for the regulation of DETCs to accelerate wound healing. Our review focuses on the above-mentioned molecular mechanisms to provide a general research framework to regulate and control the function of DETCs.

SnapshotDx Quiz: December 2020

SnapshotDx Quiz: December 2020

Single Cell Immune Profiling Reveals Distinct T Cell Clones and Functional States in in-Vitro Expanded Cord Blood Derived Gamma Delta T Cells

Gamma-delta (γδ) T cells represent a special class of unconventional T cells defined by their expression of the somatically rearranged T cell receptor (TCR) γ and δ chains. Unlike TCRαβ, it has been reported that different TCRγδ are also able to bind to their antigens in the context of non-classical MHC-like molecules or totally independent of the MHC complexes. Additionally, a variety of NK receptors are known to be expressed by γδ T cells, conferring their ability to sense alternative classes of cancer-associated antigens in a multimodal manner. Such a diverse mode of antigen recognition possibly endows γδ T cells with a wide spectrum of functional activation program. Our team had previously explored the potential of expanding cord blood (CB) derived γδ T cells (CB-gdT) as well as their corresponding ability to target primary acute myeloid leukemia (AML) cells. Using a feeder cell line-based in vitro expansion protocol, we achieved a clinically relevant scale expansion of γδ T cells over a period of 14 days. These cells exhibit variable degree of potency against a range of human AML cell lines and primary patient samples. In order to dissect the cellular and molecular programs governing the activation, differentiation and functional states of our in vitro expanded CB-gdT, we performed multiplex single cell sequencing analysis using the 10X Genomics Chromium System. After initial quality check and filtering, data from a total of 4,276 cells were retrieved. Among which, we identified 742 unique TCRγδ clonotypes, representing 18.6% of the starting 4,000 FACS purified γδ T cells seeded for expansion. The largest 10% of the clones was found to make up 60.9% of the total retrieved cells, demonstrating a significant extent of clonal focusing in our expansion cultures. Consistent to our FACS analysis, Vδ1 is the predominant TRD chain in the expanded cultures, accounting for 61.2% of all clones. Vγ4 is the most prevalent TRG chain making up to 24.9% of all clones regardless of the paired Vδ subtype. Notably, however, the largest γδ T cell clone did not utilize Vγ4, indicating that Vγ4 clones, although frequent, are not the most proliferative clone. These data are supportive of the adaptive characteristics of CB-gdTs, likely in a TCRγδ dependent manner. Based on uniform manifold approximation and projection for dimension reduction (UMAP), all cells were clustered into 11 subsets. Key cytotoxic genes including GZMB, GZMA and NKG7 were all highly expressed across all clusters, indicating that the expanded cells were indeed functionally cytotoxic. Comparing against multiple curated gene sets, we have identified 3 main subsets of γδ T cells: the Proliferative, Cytotoxic γδ T cells (P-CT), Differentiated Cytotoxic γδ T cells (D-CT) and Late Activated Cytotoxic γδ T cells (LA-CT). P-CT (~46% of all cells) shows an expression profile positively associated with cell proliferation as well as increased cell surface expression of memory T cell markers CD27, CCR7 and CD62L. Similar to cytotoxic genes, genes associated with TCR signaling and interferon response were found to be expressed across all cell clusters, yet with elevated levels in D-CT and LA-CT. Furthermore, cell surface expression of different NK receptors including NKG2D, DNAM1 and NKp30 are more enriched in LA-CT compared to the other 2 subsets, suggesting the acquisition of additional NK receptor related functions in this group of cells. Consistent with the concept of progressive γδ T cell differentiation and activation in culture, we found that in 85 (11.5%) of the γδ T cell clones bearing more than 10 cells each, all clones contain cells distributed across the 3 different γδ T cell subsets. Further analysis did not reveal any relationship between the relative proportion of the subsets within each clone with clone size nor any specific type of delta/gamma chain. Taken together, our high-resolution transcriptome analysis suggests that as CB-gdT expand and differentiate in culture, they are likely to adopt dynamic memory and signal -specific functional programs. More importantly, our data highlights the rich clonal and cellular composition of in vitro expanded CB-gdT. These unique characteristics of our CB-gdT can overcome the challenges of tumor heterogeneity and cell persistence, with the potential of improving outcomes in cell immunotherapy. Disclosures Tan: Tessa Therapeutics Ltd: Current Employment.

BTN3A1 governs antitumor responses

Cancer Immunology T lymphocytes are immune cells that can be activated through their gamma delta (γδ) or alpha beta (αβ) receptors. Both T cell types are found in human cancers, but current immunotherapies do not harness their coordinated antitumor activity. Payne et al. found that BTN3A1 and BTN2A1, two members of the butyrophilin family of proteins, partner to activate the most abundant subset of γδ T cells in peripheral blood. Antibodies targeting BTN3A1 redirect γδ T cells to attack cancer cells while also increasing the activity of tumor-specific αβ T cells. Thus, the killing of established tumors by different T cell subsets can be achieved through BTN3A1 targeting and may provide new strategies for cancer immunotherapy. Science , this issue p. [942][1] [1]: /lookup/doi/10.1126/science.aay2767

γδ T cells in malaria: a double-edged sword.

Malaria remains a devastating global health problem, resulting in many annual deaths due to the complications of severe malaria. However, in endemic regions, individuals can acquire 'clinical immunity' to malaria, characterized by a decrease in severe malaria episodes and an increase of asymptomatic Plasmodiumfalciparum infections. Recently, it has been reported that tolerance to 'clinical malaria' and reduced disease severity correlates with a decrease in the numbers of circulating Vγ9Vδ2 T cells, the major subset of γδ T cells in the human peripheral blood. This is particularly interesting as this population typically undergoes dramatic expansions during acute Plasmodium infections and was previously shown to play antiparasitic functions. Thus, regulated γδ T-cell responses may be critical to balance immune protection with severe pathology, particularly as both seem to rely on the same pro-inflammatory cytokines, most notably TNF and IFN-γ. This has been clearly demonstrated in mouse models of experimental cerebral malaria (ECM) based on Plasmodiumberghei ANKA infection. Furthermore, our recent studies suggest that the natural course of Plasmodium infection, mimicked in mice through mosquito bite or sporozoite inoculation, includes a major pathogenic component in ECM that depends on γδ T cells and IFN-γ production in the asymptomatic liver stage, where parasite virulence is seemingly set and determines pathology in the subsequent blood stage. Here, we discuss these and other recent advances in our understanding of the complex-protective versus pathogenic-functions of γδ T cells in malaria.

Microbial exposure drives polyclonal expansion of innate γδ T cells immediately after birth

Starting at birth, the immune system of newborns and children encounters and is influenced by environmental challenges. It is still not completely understood how γδ T cells emerge and adapt during early life. Studying the composition of T cell receptors (TCRs) using next-generation sequencing (NGS) in neonates, infants, and children can provide valuable insights into the adaptation of T cell subsets. To investigate how neonatal γδ T cell repertoires are shaped by microbial exposure after birth, we monitored the γ-chain (TRG) and δ-chain (TRD) repertoires of peripheral blood T cells in newborns, infants, and young children from Europe and sub-Saharan Africa. We identified a set of TRG and TRD sequences that were shared by all children from Europe and Africa. These were primarily public clones, characterized by simple rearrangements of Vγ9 and Vδ2 chains with low junctional diversity and usage of non-TRDJ1 gene segments, reminiscent of early ontogenetic subsets of γδ T cells. Further profiling revealed that these innate, public Vγ9Vδ2+ T cells underwent an immediate TCR-driven polyclonal proliferation within the first 4 wk of life. In contrast, γδ T cells using Vδ1+ and Vδ3+TRD rearrangements did not significantly expand after birth. However, different environmental cues may lead to the observed increase of Vδ1+ and Vδ3+TRD sequences in the majority of African children. In summary, we show how dynamic γδ TCR repertoires develop directly after birth and present important differences among γδ T cell subsets.

Adaptive γδ T cell function is subverted by Yersinia pseudotuberculosis outer proteins

Abstract γδ T cells are an unconventional subset of multifunctional T cells enriched in mucosal barrier tissues. After foodborne Listeria monocytes (Lm) infection, an activated CD44hiCD27loVγ4 subset of γδ T cells formed in the mesenteric lymph nodes (MLN) that shared numerous characteristics with traditional T cells including anamnestic responses. While attempting to uncover the specificity of Lm-elicited memory cells utilizing heterologous challenge infections we observed that Lm-elicited γδ T cell function was induced with heat-killed Yersinia pseudotuberculosis (Yptb) but not live Yptb suggesting that Yptb employs immune evasion strategies to limit anti-pathogen adaptive γδ T cell functions. Live Yptb inhibited CD44hiCD27loVγ4 T cell IL-17A and IFNγ production integral for anti-pathogen immunity. Tracking Yptb translocation through a FRET-based reporter assay revealed preferential translocation of Yptb outer proteins (Yop) into adaptive γδ T cells over conventional T cells and an abrogated cytokine response compared to their non-translocated counterparts within the same environment. Using a series of Yptb mutants deficient in translocated effector proteins, we determined that YopH inhibited IL-17A production while YopJ inhibited IFNγ production. Inhibition of Stat4 phosphorylation in γδ T cells was observed in a translocation, YopJ, and IL-12/IL-23p40 dependent manner, suggesting that YopJ inhibits IFNγ production through Stat4 phosphorylation. Collectively, these data demonstrate direct inhibitory mechanisms of γδ T cell function mediated by the Yptb effectors YopH and YopJ and identify an unknown pathogenesis pathway utilized by Yptb to subvert immune function.

MHC Restriction: Where Are We Now?

MHC Restriction: Where Are We Now?

γδ T Cells Kill Plasmodium falciparum in a Granzyme- and Granulysin-Dependent Mechanism during the Late Blood Stage

Plasmodium spp., the causative agent of malaria, have a complex life cycle. The exponential growth of the parasites during the blood stage is responsible for almost all malaria-associated morbidity and mortality. Therefore, tight immune control of the intraerythrocytic replication of the parasite is essential to prevent clinical malaria. Despite evidence that the particular lymphocyte subset of γδ T cells contributes to protective immunity during the blood stage in naive hosts, their precise inhibitory mechanisms remain unclear. Using human PBMCs, we confirmed in this study that γδ T cells specifically and massively expanded upon activation with Plasmodium falciparum culture supernatant. We also demonstrate that these activated cells gain cytolytic potential by upregulating cytotoxic effector proteins and IFN-γ. The killer cells bound to infected RBCs and killed intracellular P. falciparum via the transfer of the granzymes, which was mediated by granulysin in a stage-specific manner. Several vital plasmodial proteins were efficiently destroyed by granzyme B, suggesting proteolytic degradation of these proteins as essential in the lymphocyte-mediated death pathway. Overall, these data establish a granzyme- and granulysin-mediated innate immune mechanism exerted by γδ T cells to kill late-stage blood-residing P. falciparum.

Dangerous γδ T cells in aged mice.

Progressive susceptibility to tumors and infectious diseases in the elderly are a serious threat to public health in aging societies. For this reason, there is growing interest in mechanisms and predictive biomarkers that accompany and potentially cause this process. In this issue of EMBO Reports, Chen etal [1] report the surprising finding that a specific subset of γδ T cells with very limited clonal diversity strongly expands in lymph nodes of aging mice. These T cells uniformly express a T-cell receptor (TCR) composed of a Vγ6 and a Vδ1 chain and show an effector T-cell phenotype characterized by the swift production of the pro-inflammatory cytokine interleukin-17 (IL-17) upon exvivo stimulation (γδT17 cells). Since γδT17 cells are suspected to be pro-tumorigenic [2], the authors next compared how mice of different age coped with an experimental lung cancer challenge and found impaired anti-tumor responses in old mice. Based on these observations, they propose a link between changes of the composition of γδ T cells in the aging lymph nodes and increased risk of cancer development in aged mice.

Abstract 934: γδ CAR T-cell therapy significantly mitigates bone metastatic castrate-resistant prostate cancer

Abstract Bone metastasis is a frequent complication in advanced prostate cancer, with the resultant lesions significantly contributing to patient morbidity and mortality. While next generation hormone ablation therapies and bone protecting bisphosphonates alleviate these symptoms, the disease remains incurable, and new therapeutic approaches are of urgent need. In this regard, we have focused on tapping the tumor-seeking potential of chimeric antigen receptor (CAR) T cells. CAR T cells have shown remarkable anti-tumor responses in hematologic malignancies, but unique physical and biological challenges have hindered their activity in solid tumors. Interestingly, patients treated with bisphosphonates such as zoledronate exhibit enhanced recruitment and activation of the γδ subset of T cells in bone due intracellular accumulation of isopentenyl pyrophosphate (IPP) phosphoantigen. Whereas conventional CAR T cell therapies utilize αβ T cells, we posit that designing γδ CAR T cells could improve homing to bone metastases when administered with bisphosphonates. First, to test the impact of prostate specific stem cell antigen (PSCA)-specific γδ CAR T cells against bone metastatic prostate cancer in vivo, NSG mice (n=10) were intratibially injected with PSCA/luciferase-expressing C4-2B (2x105) castrate resistant prostate cancer cells. Tumors were allowed to establish for 10 days and then randomized into control or γδ CAR T (1.5x107 via tail vein) groups. Subsequent bioluminescent imaging indicated a rapid and significant (p=0.0006) regression of tumors in the γδ CAR T cell group, leading to increased overall survival (5/5 γδ CAR T vs. 0/5 control after 68 days, p=0.0002). Ex vivo bone morphometry analysis also demonstrated the significant protective effect of γδ CAR T associated bone disease. To determine whether bisphosphonates could further enhance the homing of γδ CAR T to bone, NSG mice (n=30) were intratibially injected with C4-2B (2x105), and randomized into control and zoledronate (30µg/kg) groups. After 10 days, mice received γδ T cells (3x106). Subsets were sacrificed at 1, 3, and 5 days post-T cell administration, and peripheral blood, tibia bone marrow, and spleens isolated. CD3-Vδ2 flow cytometry indicated increased γδ T cells in the tibia bone marrow from zoledronate groups (Day 1=61%, Day 3=32%, and Day 5=57%). Furthermore, decreased tumor growth rates were observed in the zoledronate group, suggesting that increased homing of γδ T cells induced anti-tumor effects. Our data to date demonstrate that γδ CAR T cells significantly mitigate bone metastatic prostate cancer and associated bone disease. Further, bisphosphonates (already used in the clinical setting) enhance the homing of γδ CAR T cells to the tumor-bone microenvironment. We posit that γδ CAR T will be an effective immunotherapy approach for the treatment of men with incurable bone metastatic prostate cancer. Citation Format: Jeremy Steven Frieling, Maria Cecilia Ramello, Ismahene Benzaid, Emiliano Roselli, Chen Hao Lo, Conor C. Lynch, Daniel Abate-Daga. γδ CAR T-cell therapy significantly mitigates bone metastatic castrate-resistant prostate cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 934.

Production of IL-17A by different subsets of γδ T cells in response to the commensal Corynebacterium mastitidis has distinct requirements for IL-1R and TCR recognition

Abstract The ocular surface is a mucosal site that interacts with the environment and protects the eye. We previously identified an ocular surface commensal, Corynebacterium mastitidis (C. mast.), which induced IL-17A production from γδ T cells in the conjunctiva, affording protection from infection. In the current study we dissect the requirement for IL-17A production in response to C. mast by Vγ4+and Vγ4−γδ T cell subsets. We found that colonization of C. mast-negative mice with C. mast. increased the frequency of IL-17A+ cells in eye-draining lymph nodes by several fold in both subsets. However, whereas Vγ4−γδ T cells upregulated their expression of IL-1R, Vγ4+γδ cells downregulated their CD3 expression, possibly secondary to TCR engagement. To examine this further, we performed in vitro co-cultures of dendritic cells and γδ T cells. With C. mast as the sole stimulant, only Vγ4+ cells, but not Vγ4− cells, produced IL-17A. Addition of exogenous IL1 to the co-cultures elicited production of IL-17A also from the Vγ4− subset, whereas inhibition of downstream TCR signaling events by FK-506 or CsA abrogated IL-17A production in the Vγ4+ subset. Furthermore, C. mast produced a positive Nur77-GFP signal only in the Vγ4+ subset. IL-1R blocking antibody abrogated IL-17A production in both subsets. We propose that Vγ4+and Vγ4− subsets may sense and respond to C. mast by IL-17A production using distinct pathways. Although an IL-1R signal is needed by both subsets, their level of dependence on this signal differs. IL-1R signaling is dominant in Vγ4−γδ T cells, whose TCR does not appear to respond to C. mast. In contrast, a much lower level of IL-1 appears to be sufficient for triggering IL-17A production from Vγ4+ γδ T cells, which recognize C. mast via their TCR.

A Longitudinal Study of γδ T Cell Subsets Post Lung Transplant: Potential Players in CMV Immunity

Purpose Cytomegalovirus (CMV) is the predominant opportunistic infection in lung transplant (LTx) recipients and there is a need to develop biomarkers that indicate CMV immunity. To this end, we have recently reported that natural killer (NK) cells expressing the activating receptor, CD94-NKG2C, may be important in the control of CMV following LTx. γδ T cells can also aid in CMV immunity, yet their role following LTx is unknown. In this study, we longitudinally assessed the phenotype of γδ T cells in the blood of LTx recipients with and without CMV reactivation. Methods Cryopreserved peripheral blood mononuclear cells (PBMC) from LTx recipients treated at the Alfred Hospital were examined by multicolour flow cytometry. Patients were stratified by risk of CMV infection into low risk (CMV donor (D) negative (-), CMV recipient (R) -, n=6), moderate risk (CMV R positive (+), n=13 (n=6 no CMV reactivation, n=7 with CMV reactivation) or high risk (CMV D+, R-) n=12 (n=5 no CMV reactivation, n=7 with CMV reactivation). CMV reactivation was classified as CMV PCR positive (>150 copies/ml) in blood and/or BAL within the first 12-months following LTx. The phenotype of γδ T cells from the LTx recipients was assessed at pre-LTx and 0.5, 1.5, 3, 6, 9, 12- and 18-months post-LTx (where available). We then compared γδ T cell phenotype between LTx recipients with and without CMV reactivation to healthy non-transplant donors (n=12). Results There was an increase in the proportion of γδ T cells expressing the Vδ1 receptor in LTx recipients compared to healthy controls, reaching significance in all CMV risk groups at 18-months post-LTx. At all time-points, there was a higher proportion of γδ T cells expressing NKG2C in moderate CMV risk recipients only without CMV reactivation compared to healthy controls. Conversely, in high CMV risk recipients with CMV, an increased proportion of γδ T cells expressed NKG2C at 18-months post-transplant compared to healthy controls. Conclusion Subsets of γδ T cells could be linked with control of CMV following LTx. Moreover, the NK cell receptor CD94-NKG2C is seemingly important in the control of CMV by multiple cell types. In conclusion, we have demonstrated that γδ T cells are an active and dynamic component of the LTx environment and may have utility as a biomarker following LTx, particularly when used in combination with NK cell analysis.

Increased frequency of systemic pro-inflammatory V\u03b41+ \u03b3\u03b4 T cells in HIV elite controllers correlates with gut viral load

γδ T cells predominate in the intestinal mucosa and help maintain gut homeostasis and mucosal immunity. Although HIV infection significantly alters these cells, what drives these perturbations is unclear. Growing evidence suggests that impaired intestinal immune function in HIV leads to chronic immune activation and disease progression. This occurs even in HIV controllers – individuals with undetectable HIV viremia without antiretroviral therapy (ART). We show that Vδ1+ cells, a subset of γδ T cells described as being important in intestinal barrier function, increase in frequency in HIV-infected individuals, including HIV controllers. These cells resemble terminally differentiated effector memory cells, producing the pro-inflammatory cytokines IFNγ, TNFα, and MIP-1β upon stimulation. Importantly, pro-inflammatory Vδ1+ cell frequency correlates with levels of HIV RNA in intestinal tissue but not in plasma. This study supports a model in which local viral replication in the gut in HIV controllers disrupts the phenotype and function of Vδ1+ cells, a cell type involved in the maintenance of epithelial barrier integrity, and may thereby contribute to systemic immune activation and HIV disease progression.

Quantification and phenotypic characterization of peripheral blood Vδ1 + T cells in chronic lymphocytic leukemia and monoclonal B cell lymphocytosis.

Vδ1+ T cells, a subset of γδ T cells, are responsible for innate-like immune responses. Recently, an anti-tumor function mediated by MHC-unrestricted recognition of lipid and stress molecules, has also been described in these cells. This study aimed to quantify and phenotypically characterize circulating Vδ1+ T cells in B cell Chronic Lymphocytic Leukemia (CLL) and Monoclonal B cell lymphocytosis (MBL). This study enrolled 58 individuals distributed in five groups: Binet B and C CLL (n = 9), Binet A CLL (n = 26), High count-MBL (n = 10), Low count-MBL (n = 5), and a control group (n = 8). The phenotypic characterization of Vδ1+ T cells, as well as the other T cell subpopulations (CD4+ , CD8+ , CD4+ /CD8+ , and Vδ1- γδT cells), were assessed by flow cytometry, evaluating the frequency of each subset expressing CD27, CD69, and cytoplasmic granzyme B. We observed an increasing percentage of Vδ1+ T cells belonging to CD27- compartment from controls to advanced stages of the disease, which was accompanied by an increasing percentage of these cells expressing granzyme B, a phenotypic pattern that was also observed in the other T cell subpopulations under study since earlier stages of the disease. Moreover, a striking expansion of Vδ1+ T cells in Binet B and C CLL was observed. These experiment findings point to an expansion of CD27- Vδ1+ T cells with a cytotoxic profile, from controls to advanced stages of the disease, which points to a role of Vδ1+ T cells in the host's anti-tumor responses against clonal B-cells in MBL and CLL. © 2018 Clinical Cytometry Society.

Syndecan-1 Regulates Psoriasiform Dermatitis by Controlling Homeostasis of IL-17-Producing γδ T Cells.

IL-17 is a potent proinflammatory cytokine that drives pathogenesis of multiple autoimmune diseases, including psoriasis. A major source of pathogenic IL-17 is a subset of γδ T cells (Tγδ17) that acquires the ability to produce IL-17 while developing in the thymus. The mechanisms that regulate homeostasis of Tγδ17 cells and their roles in psoriasis, however, are not fully understood. In this paper, we show that the heparan sulfate proteoglycan syndecan-1 (sdc1) plays a critical role in regulating homeostasis of Tγδ17 cells and modulating psoriasis-like skin inflammation in mice. sdc1 was predominantly expressed by Tγδ17 cells (but not IL-17- Tγδ cells) in the thymus, lymph nodes, and dermis. sdc1 deficiency significantly and selectively increased the frequency and absolute numbers of Tγδ17 cells by mechanisms that included increased proliferation and decreased apoptosis. Adoptive transfer experiments ruled out a significant role of sdc1 expressed on nonhematopoietic cells in halting expansion and proliferation of sdc1-deficient Tγδ17 cells. When subjected to imiquimod-induced psoriasiform dermatitis, Tγδ17 cells in sdc1KO mice displayed heightened responses accompanied by significantly increased skin inflammation than their wild-type counterparts. Furthermore, transferred sdc1-deficient γδ T cells caused more severe psoriasiform dermatitis than their sdc1-sufficient counterparts in TCR-βδ KO hosts. The results uncover a novel role for sdc1 in controlling homeostasis of Tγδ17 cells and moderating host responses to psoriasis-like inflammation.

LB1559 Gut microbe sensing IL17+Vγ6+ γδ T-cells modulate cutaneous inflammation

The microbiota colonizes all barrier sites where it is known to dramatically influence local immunity. We set out to address the question of whether the microbiota also promotes crosstalk between barrier tissues. To address this question, we monocolonized germ-free with the gut-resident bacteria, segmented filamentous bacteria (SFB) that is known to promote type 17 immune responses. We found that in addition of classical T cells, SFB leads to accumulation of IL17+Vγ6+ gd T-cells both within the gut and systemically. We then treated these mice with FTY720, which inhibits egress from lymph nodes and showed that IL17+Vγ6+ still accumulate in gut-associated tissues while leading to fewer IL17+Vγ6+ in the skin. We then tested the pathological relevance of this finding by using the imiquimod murine model of psoriasis. We found that gut-bacteria colonized mice had a more robust skin inflammatory response. We then hypothesized that high-fat diet (HFD) induced gut dysbiosis could lead to a similar phenotype. Indeed, we found that a HFD leads to a massive expansion of IL17+Vγ6+ in the skin, an effect that is completely abrogated upon the administration of the gut specific antibiotics vancomycin and neomycin. Additionally, we found that a HFD leads to more robust inflammation in the imiquimod model of psoriasis, and that this effect can be ameliorated with gut-specific antibiotics or with the abolition of IL-1 signaling. These findings support the idea that the gut microbiota can have a profound influence in the severity of skin inflammatory disorders and that this effect may be mediated by a defined subset of γδ T cells. One can speculate that such a mechanism could be beneficial in certain contexts where microbial insults to the host at one barrier site can heighten the host’s defenses systemically for preparation against subsequent attacks. However, this mechanism can be detrimental in the context of inflammatory disease, where in the context of a genetically predisposed individual, microbial fluctuations in the gut can lead to flares and exacerbations of psoriasis.

From the Editor’s desk....: September 2018

From the Editor’s desk....: September 2018

New Insights Into the Regulation of Natural-Killer Group 2 Member D (NKG2D) and NKG2D-Ligands: Endoplasmic Reticulum Stress and CEA-Related Cell Adhesion Molecule 1.

Natural-killer group 2 member D (NKG2D) is a well-characterized activating receptor expressed by natural killer (NK) cells, NKT cells, activated CD8+ T cells, subsets of γδ+ T cells, and innate-like T cells. NKG2D recognizes multiple ligands (NKG2D-ligands) to mount an innate immune response against stressed, transformed, or infected cells. NKG2D-ligand surface expression is tightly restricted on healthy cells through transcriptional and post-transcriptional mechanisms, while transformed or infected cells express the ligands as a danger signal. Recent studies have revealed that unfolded protein response pathways during endoplasmic reticulum (ER) stress result in upregulation of ULBP-related protein via the protein kinase RNA-like ER kinase-activating factor 4-C/EBP homologous protein (PERK-ATF4-CHOP) pathway, which can be linked to the pathogenesis of autoimmune diseases. Transformed cells, however, possess mechanisms to escape NKG2D-mediated immune surveillance, such as upregulation of carcinoembryonic antigen (CEA)-related cell adhesion molecule 1 (CEACAM1), a negative regulator of NKG2D-ligands. In this review, we discuss mechanisms of NKG2D-ligand regulation, with a focus on newly discovered mechanisms that promote NKG2D-ligand expression on epithelial cells, including ER stress, and mechanisms that suppress NKG2D-ligand-mediated killing of cancer cells, namely by co-expression of CEACAM1.

Lymph node \u03b3\u03b4 and \u03b1\u03b2 CD8+ T cells share migratory properties

During immune responses, T cells differentiate into subsets with different functions and migratory properties. Here we characterize migratory behavior of endogenous αβ CD8+ and γδ T cells in lymph nodes by long-term tracking following in vivo photoconversion. We identified subsets of γδ T cells with distinct circulation kinetics that closely mirrored migratory subsets of αβ CD8+ T cells. Notably, αβ CD8+ and γδ T cells both comprised resident populations which stayed in lymph nodes for 4 weeks without circulation or proliferation. Furthermore, in contrast to the common conception, we observed that central memory αβ CD8+ T cells circulate with slower kinetics than naïve cells. Our results show that, similar to αβ T cells, γδ T cells can acquire distinct migratory properties during their development and differentiation and reveal unexpected intricacies of T cell migratory patterns.