Global characterization of differential gene expression profiles in mouse Vγ1+ and Vγ4+ γδ T cells

Vγ1 and Vγ4 gamma-delta T cells play opposing roles in the immunopathology of traumatic brain injury in males

Traumatic brain injury (TBI) is a leading cause of morbidity and mortality. The innate and adaptive immune responses play an important role in the pathogenesis of TBI. Gamma-delta (γδ) T cells have been shown to affect brain immunopathology in multiple different conditions, however, their role in acute and chronic TBI is largely unknown. Here, we show that γδ T cells affect the pathophysiology of TBI as early as one day and up to one year following injury in a mouse model. TCRδ^-/- mice are characterized by reduced inflammation in acute TBI and improved neurocognitive functions in chronic TBI. We find that the Vγ1 and Vγ4 γδ T cell subsets play opposing roles in TBI. Vγ4 γδ T cells infiltrate the brain and secrete IFN-γ and IL-17 that activate microglia and induce neuroinflammation. Vγ1 γδ T cells, however, secrete TGF-β that maintains microglial homeostasis and dampens TBI upon infiltrating the brain. These findings provide new insights on the role of different γδ T cell subsets after brain injury and lay down the principles for the development of targeted γδ T-cell-based therapy for TBI.

Cell autonomous expression of BCL6 is required to maintain lineage identity of mouse CCR6+ ILC3s

Innate lymphoid cells (ILC) are similar to T helper (Th) cells in expression of cytokines and transcription factors. For example, RORγt is the lineage-specific transcription factor for both ILC3 and Th17 cells. However, the ILC counterpart for BCL6-expressing T follicular helper (Tfh) cells has not been defined. Here, we report that in the ILC compartment, BCL6 is selectively co-expressed with not only CXCR5 but also RORγt and CCR6 in ILC3 from multiple tissues. BCL6-deficient ILC3 produces enhanced levels of IL-17A and IL-22. More importantly, phenotypic and single-cell ATAC-seq analysis show that absence of BCL6 in mature ILC3 increases the numbers of ILC1 and transitional cells co-expressing ILC3 and ILC1 marker genes. A lineage-tracing experiment further reveals BCL6+ ILC3 to ILC1 trans-differentiation under steady state. Finally, microbiota promote BCL6 expression in colonic CCR6+ ILC3 and thus reinforce their stability. Collectively, our data have demonstrated that CCR6+ ILC3 have both Th17 and Tfh programs and that BCL6 expression in these cells functions to maintain their lineage identity.

Skin γδ T Cells and Their Function in Wound Healing

For the skin immune system, γδ T cells are important components, which help in defensing against damage and infection of skin. Compared to the conventional αβ T cells, γδ T cells have their own differentiation, development and activation characteristics. In adult mice, dendritic epidermal T cells (DETCs), Vγ4 and Vγ6 γδ T cells are the main subsets of skin, the coordination and interaction among them play a crucial role in wound repair. To get a clear overview of γδ T cells, this review synopsizes their derivation, development, colonization and activation, and focuses their function in acute and chronic wound healing, as well as the underlining mechanism. The aim of this paper is to provide cues for the study of human epidermal γδ T cells and the potential treatment for skin rehabilitation.

Vγ4 T cell-derived IL-17A is essential for amplification of inflammatory cascades in ischemic brain tissue after stroke

BACKGROUND

Through amplifying inflammatory cascades, IL-17A produced by γδ T cells potently attracts neutrophils to the site of injury for exacerbating ischemic tissue damage. Our goal was to identify the precise role of γδ T cell subsets in ischemic brain tissue damage of stroke.

METHODS

In a model of experimental stroke, we analyzed the functions of Vγ1 and Vγ4 T cells on γδ T cell-mediated ischemic brain tissue damage of stroke.

RESULTS

We identified that, in stroke, Vγ4 T cells are essential for γδ T cell-mediated ischemic brain tissue damage through providing an early source of IL-17A. Both CCL20 and IL-1β/IL-23 are deeply involved in Vγ4 T cell-mediated amplification of inflammatory responses: CCL20 might promote Vγ4 T cells recruit to infract hemisphere, and IL-1β/IL-23 powerfully enhance IL-17A production mediated by the infiltrating Vγ4 T cells. Moreover, Vγ4 T cell-derived IL-17A enhances both CCL20 and IL-1β, and conversely, CCL20 and IL-1β further enhance both recruitment and IL-17A production of IL-17A-positive cells, in a classic positive feedback loop.

CONCLUSION

Our data suggest that in the setting of ischemic stroke, Vγ4 T cell-derived IL-17A, CCL20 and IL-1β/IL-23 in infract hemisphere coordinately to amplify inflammatory cascades and exacerbate ischemic tissue damage.

Gamma Delta T Cells and Their Pathogenic Role in Psoriasis

γδT cells are an unconventional population of T lymphocytes that play an indispensable role in host defense, immune surveillance, and homeostasis of the immune system. They display unique developmental, distributional, and functional patterns and rapidly respond to various insults and contribute to diverse diseases. Although γδT cells make up only a small portion of the total T cell pool, emerging evidence suggest that aberrantly activated γδT cells may play a role in the pathogenesis of psoriasis. Dermal γδT cells are the major IL-17-producing cells in the skin that respond to IL-23 stimulation. Furthermore, γδT cells exhibit memory-cell-like characteristics that mediate repeated episodes of psoriatic inflammation. This review discusses the differentiation, development, distribution, and biological function of γδT cells and the mechanisms by which they contribute to psoriasis. Potential therapeutic approaches targeting these cells in psoriasis have also been detailed.

Lactobacillus acidipiscis Induced Regulatory Gamma Delta T Cells and Attenuated Experimental Autoimmune Encephalomyelitis

Multiple sclerosis is a chronic autoimmune disease involving the central nervous system, and shows a high disability rate. Its pathogenesis is complicated, and there is no good treatment. In recent years, with in-depth studies on the regulation of gastrointestinal flora, the relationship between the mammalian immune system and the intestinal flora has been extensively explored. Changes in the composition and structure of the gastrointestinal flora can affect the characteristics and development of the host immune system and even induce a series of central nervous system inflammation events. The occurrence and development of multiple sclerosis are closely related to the continuous destruction of the intestinal barrier caused by intestinal dysbacteriosis. In this study, we analyzed Lactobacillus acidipiscis in a mouse model of experimental autoimmune encephalomyelitis (EAE). We found that the amount of L. acidipiscis in the intestinal tract was inversely proportional to the progress of EAE development. In addition, the number of CD4+ FOXP3+ regulatory T cells in the mesenteric lymph nodes of mice increased significantly after the mice were fed with L. acidipiscis, and the differentiation of CD4+ T cells to Th1 and Th17 cells was inhibited. However, the protective effect of L. acidipiscis was lost in γδ T cell-deficient mice and hence was concluded to depend on the presence of regulatory γδ T cells in the intestinal epithelium. Moreover, including L. acidipiscis enhanced the development of Vγ1+γδ T cells but suppressed that of Vγ4+γδ T cells. In summary, our results demonstrated the ability of L. acidipiscis to induce generation of regulatory γδ T cells that suppress the development of the encephalomyelitic Th1 and Th17 cells and the progress of EAE.

γδ T cells shape memory-phenotype αβ T cell populations in non-immunized mice

Size and composition of γδ T cell populations change dramatically with tissue location, during development, and in disease. Given the functional differentiation of γδ T cell subsets, such shifts might alter the impact of γδ T cells on the immune system. To test this concept, and to determine if γδ T cells can affect other immune cells prior to an immune response, we examined non-immunized mice derived from strains with different genetically induced deficiencies in γδ T cells, for secondary changes in their immune system. We previously saw extensive changes in pre-immune antibodies and B cell populations. Here, we report effects on αβ T cells. Similarly to the B cells, αβ T cells evidently experience the influence of γδ T cells at late stages of their pre-immune differentiation, as single-positive heat stable antigen-low thymocytes. Changes in these and in mature αβ T cells were most prominent with memory-phenotype cells, including both CD8+ and CD4+ populations. As previously observed with B cells, most of the effects on αβ T cells were dependent on IL-4. Unexpectedly, IL-4 seemed to be produced mainly by αβ T cells in the non-immunized mice, albeit strongly regulated by γδ T cells. Similarly to our findings with B cells, changes of αβ T cells were less pronounced in mice lacking all γδ T cells than in mice lacking only some, suggesting that the composition of the γδ T cell population determines the nature of the γδ-influence on the other pre-immune lymphocytes.

Vγ4+γδT Cells Aggravate Severe H1N1 Influenza Virus Infection-Induced Acute Pulmonary Immunopathological Injury via Secreting Interleukin-17A

The influenza A (H1N1) pdm09 virus remains a critical global health concern and causes high levels of morbidity and mortality. Severe acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are the major outcomes among severely infected patients. Our previous study found that interleukin (IL)-17A production by humans or mice infected with influenza A (H1N1) pdm09 substantially contributes to ALI and subsequent morbidity and mortality. However, the cell types responsible for IL-17A production during the early stage of severe influenza A (H1N1) pdm09 infection remained unknown. In this study, a mouse model of severe influenza A (H1N1) pdm09 infection was established. Our results show that, in the lungs of infected mice, the percentage of γδT cells, but not the percentages of CD4⁺Th and CD8⁺Tc cells, gradually increased and peaked at 3 days post-infection (dpi). Further analysis revealed that the Vγ4⁺γδT subset, but not the Vγ1⁺γδT subset, was significantly increased among the γδT cells. At 3 dpi, the virus induced significant increases in IL-17A in the bronchoalveolar lavage fluid (BALF) and serum. IL-17A was predominantly secreted by γδT cells (especially the Vγ4⁺γδT subset), but not CD4⁺Th and CD8⁺Tc cells at the early stage of infection, and IL-1β and/or IL-23 were sufficient to induce IL-17A production by γδT cells. In addition to secreting IL-17A, γδT cells secreted interferon (IFN)-γ and expressed both an activation-associated molecule, natural killer group 2, member D (NKG2D), and an apoptosis-associated molecule, FasL. Depletion of γδT cells or the Vγ4⁺γδT subset significantly rescued the virus-induced weight loss and improved the survival rate by decreasing IL-17A secretion and reducing immunopathological injury. This study demonstrated that, by secreting IL-17A, lung Vγ4⁺γδT cells, at least, in part mediated influenza A (H1N1) pdm09-induced immunopathological injury. This mechanism might serve as a promising new target for the prevention and treatment of ALI induced by influenza A (H1N1) pdm09.

Impact of aging immune system on neurodegeneration and potential immunotherapies

The interaction between the nervous and immune systems during aging is an area of avid interest, but many aspects remain unclear. This is due, not only to the complexity of the aging process, but also to a mutual dependency and reciprocal causation of alterations and diseases between both the nervous and immune systems. Aging of the brain drives whole body systemic aging, including aging-related changes of the immune system. In turn, the immune system aging, particularly immunosenescence and T cell aging initiated by thymic involution that are sources of chronic inflammation in the elderly (termed inflammaging), potentially induces brain aging and memory loss in a reciprocal manner. Therefore, immunotherapeutics including modulation of inflammation, vaccination, cellular immune therapies and "protective autoimmunity" provide promising approaches to rejuvenate neuroinflammatory disorders and repair brain injury. In this review, we summarize recent discoveries linking the aging immune system with the development of neurodegeneration. Additionally, we discuss potential rejuvenation strategies, focusing aimed at targeting the aging immune system in an effort to prevent acute brain injury and chronic neurodegeneration during aging.

Changes of peripheral blood Vδ1 T cells in patients with atherosclerotic cerebral infarction

To observe the ratio of peripheral blood Vδ1 T cells in patients with atherosclerotic cerebral infarction (ACI) and their function changes, and preliminarily explore the mechanism of change in ratio of peripheral blood Vδ1 T cells in ACI patients. 30 ACI patients enrolled in the neurology department in our hospital from January 2016 to December 2016 were selected, and 30 healthy subjects enrolled in the hospital during the same period were selected as healthy controls. Peripheral blood mononuclear cells (PBMC) were obtained by density gradient centrifugation. The ratio of Vδ1 T cells in peripheral blood of ACI patients was detected by flow cytometry, and the correlations between the ratio of Vδ1 T cells and the neurological deficits and infarction size in ACI patients were analyzed. A high proportion of Vδ1 T cells were obtained by in vitro amplification, and high-purity Vδ1 T cells and Naïve CD4 T cells were obtained by flow cytometry and magnetic bead sorting respectively. The effect of Vδ1 T cells on the proliferation of Naïve CD4 T cells and the secretion of IFN-γ were investigated by CFSE staining method; the correlation between the ratio of Vδ1 T cells in peripheral blood and the Ox-LDL level in peripheral blood of ACI patients was analyzed. The Vδ1 T cells in peripheral blood were treated by Ox-LDL, and the effect of Ox-LDL on Vδ1 T cell apoptosis was determined by apoptosis staining method. Compared with the healthy control group, the ratio of Vδ1 T cells in peripheral blood of ACI patients was significantly decreased (P<0.0001). The ratio of Vδ1 T cells in peripheral blood of ACI patients was not significantly correlated with age, sex, hypertension, diabetes and dyslipidemia (P>0.05). However, with the gradual aggravation of neurological deficit and gradual increase of infarct volume, the ratio of Vδ1 T cells in peripheral blood of ACI patients decreased gradually. Besides, the functional studies showed that the immunosuppressive functions of Vδ1 T cells in peripheral blood of ACI patients were also significantly decreased (P<0.0001). The ratio of Vδ1 T cells in peripheral blood of ACI patients was negatively correlated with the Ox-LDL level in peripheral blood (r²=0.1691; P=0.0240); the Ox-LDL treatment of Vδ1 T cells induced apoptosis of Vδ1 T cells, and with the increased Ox-LDL concentration, the ratio of Vδ1 T cell apoptosis gradually increased. The decreased ratio of Vδ1 T cells in peripheral blood and loss of functions in ACI patients lead to the occurrence of immunoinflammatory reactions, which may be one of the possible causes of ACI. In addition, this study also showed that, Ox-LDL could induce Vδ1 T cell apoptosis and lead to decrease in ratio of Vδ1 T cells in peripheral blood, which may be one of the reasons for decreased ratio of Vδ1 T cells in peripheral blood of ACI patients. In summary, this study can further help the understanding of the pathogenesis of ACI.

γδ T Cells and B Cells

γδ T cells constitute the third arm of a tripartite adaptive immune system in jawed vertebrates, besides αβ T cells and B cells. Like the other two lymphocyte-types, they express diverse antigen receptors, capable of specific ligand recognition. Functionally, γδ T cells represent a system of differentiated subsets, sometimes engaged in cross-regulation, which ultimately determines their effect on other components of the immune system, including B cells and antibodies. γδ T cells are capable of providing help to B cells in antibody production. More recently it became clear that γδ T cells influence B cell differentiation during the peripheral stages of B cell development, control levels of circulating immunoglobulin (all subclasses), and affect production of autoantibodies. Because of this relationship between γδ T cells and B cells, the extensive variation of γδ T cells among human individuals might be expected to modulate their humoral responsiveness.

Vγ1+γδT, early cardiac infiltrated innate population dominantly producing IL-4, protect mice against CVB3 myocarditis by modulating IFNγ+ T response

Viral myocarditis (VMC) is an inflammation of the myocardium closely associated with Coxsackievirus B3 (CVB3) infection. Vγ1⁺γδT cells, one of early cardiac infiltrated innate population, were reported to protect CVB3 myocarditis while the precise mechanism not fully addressed. To explore cytokine profiles and kinetics of Vγ1⁺γδT and mechanism of protection against VMC, flow cytometry was conducted on cardiac Vγ1 cells in C57BL/6 mice following CVB3 infection. The level of cardiac inflammation, transthoracic echocardiography and viral replication were evaluated after monoclonal antibody depletion of Vγ1γδT. We found that Vγ1⁺γδT cells infiltration peaked in the heart at day3 post CVB3 infection and constituted a minor source of IFN-γ but major producers for early IL-4. Vγ1γδT cells were activated earlier holding a higher IL-4-producing efficiency than CD4⁺Th cells in the heart. Depletion of Vγ1⁺γδT resulted in a significantly exacerbated cardiac infiltration, increased T, macrophage and neutrophil population in heart homogenates and worse cardiomyopathy; which was accompanied by a significant expansion of peripheral IFNγ⁺CD4+ and CD8+T cells. Neutralization of IL-4 in mice resulted in an exacerbated acute myocarditis confirming the IL-4-mediated protective mechanism of Vγ1. Our findings identify a unique property of Vγ1⁺γδT cells as one dominant early producers of IL-4 upon CVB3 acute infection which is a key mediator to protect mice against acute myocarditis by modulating IFNγ-secreting T response.

γδ T Cells Shape Preimmune Peripheral B Cell Populations

We previously reported that selective ablation of certain γδ T cell subsets, rather than removal of all γδ T cells, strongly affects serum Ab levels in nonimmunized mice. This type of manipulation also changed T cells, including residual γδ T cells, revealing some interdependence of γδ T cell populations. For example, in mice lacking Vγ4(+) and Vγ6(+) γδ T cells (B6.TCR-Vγ4(-/-)/6(-/-)), we observed expanded Vγ1(+) cells, which changed in composition and activation and produced more IL-4 upon stimulation in vitro, increased IL-4 production by αβ T cells as well as spontaneous germinal center formation in the spleen, and elevated serum Ig and autoantibodies. We therefore examined B cell populations in this and other γδ-deficient mouse strains. Whereas immature bone marrow B cells remained largely unchanged, peripheral B cells underwent several changes. Specifically, transitional and mature B cells in the spleen of B6.TCR-Vγ4(-/-)/6(-/-) mice and other peripheral B cell populations were diminished, most of all splenic marginal zone (MZ) B cells. However, relative frequencies and absolute numbers of Ab-producing cells, as well as serum levels of Abs, IL-4, and BAFF, were increased. Cell transfers confirmed that these changes are directly dependent on the altered γδ T cells in this strain and on their enhanced potential of producing IL-4. Further evidence suggests the possibility of direct interactions between γδ T cells and B cells in the splenic MZ. Taken together, these data demonstrate the capability of γδ T cells of modulating size and productivity of preimmune peripheral B cell populations.