Human γδ T Cells Induce Dendritic Cell Maturation

γδ T cells are known to be involved in the innate immune defenses against infectious microorganisms. Herein, we considered that γδ T cells could also influence adaptative immunity by interacting with dendritic cells (DC) in the early phase of the immune response. To investigate this hypothesis, γδ T cells isolated from the peripheral blood of healthy volunteers were cocultured with autologous monocyte-derived dendritic cells, which were subsequently analyzed for their expression of key surface molecules and for their production of IL-12. First, we found that γδ T cells induced the upregulation of HLA-DR, CD86, and CD83 on DC. This effect did not require cell to cell contact and could be blocked by a neutralizing anti-TNF antibody. We then observed that γδT cells activated by the synthetic phosphoantigen bromohydrin pyrophosphate (BrHPP) induced the production of IL-12 (p40) and IL-12 (p70) by DC, an effect that involved IFN-γ production. The relevance of this finding to DC function was demonstrated by the increased production of IFN-γ by alloreactive T cells when stimulated in a mixed leucocyte reaction with DC preincubated with activated γδ T cells. We conclude that γδ T cell activation might result in DC maturation and thereby in enhanced αβ T cell responses.     

TLR2‐activated human langerhans cells promote Th17 polarization via IL‐1β, TGF‐β and IL‐23

The cytokines IL‐6, IL‐1β, TGF‐β, and IL‐23 are considered to promote Th17 commitment. Langerhans cells (LC) represent DC in the outer skin layers of the epidermis, an environment extensively exposed to pathogenic attack. The question whether organ‐resident DC like LC can evoke Th17 immune response is still open. Our results show that upon stimulation by bacterial agonists, epidermal LC and LC‐like cells TLR2‐dependently acquire the capacity to polarize Th17 cells. In Th17 cells, expression of retinoid orphan receptor γβ was detected. To clarify if IL‐17⁺cells could arise per se by stimulated LC we did not repress Th1/Th2 driving pathways by antibodies inhibiting differentiation. In CD1c⁺/langerin⁺ monocyte‐derived LC‐like cells (MoLC), macrophage‐activating lipopeptide 2, and peptidoglycan (PGN) induced the release of the cytokines IL‐6, IL‐1β, and IL‐23. TGF‐β, a cytokine required for LC differentiation and survival, was found to be secreted constitutively. Anti‐TLR2 inhibited secretion of IL‐6, IL‐1β, and IL‐23 by MoLC, while TGF‐β was unaffected. The amount of IL‐17 and the ratio of IL‐17 to IFN‐γ expression was higher in MoLC‐ than in monocyte‐derived DC‐cocultured Th cells. Anti‐IL‐1β, ‐TGF‐β and ‐IL‐23 decreased the induction of Th17 cells. Interestingly, blockage of TLR2 on PGN‐stimulated MoLC prevented polarization of Th cells into Th17 cells. Thus, our findings indicate a role of TLR2 in eliciting Th17 immune responses in inflamed skin.     

Mannan Derivatives Instruct Dendritic Cells to Induce Th1/Th2 Cells Polarization via Differential Mitogen‐Activated Protein Kinase Activation

Mannan derived from fungal cell walls have potential uses as immunomodulating agents and vaccine adjuvants. Immunization with antigen conjugated to oxidized mannan (OM) or reduced mannan (RM) have induced differential immune responses in mice. Yet, the adjuvant effect and differences in molecular profiles of OM and RM on APCs is unresolved. Here, we investigated the response of mouse bone marrow‐derived DCs to OM and RM. OM and RM stimulated DCs to produce differential Th1/Th2‐inducing cytokines in vitro. OM and RM‐activated DCs stimulated allogeneic T‐cell Th1 and Th2 polarization reaction. OM instruct DCs to stimulate Th1 responses via IL‐12p70 production, which depends on the phosphorylation of p38, RM barely induce IL‐12p70, but IL‐10 and IL‐4, and magnitude of ERK phosphorylation, which results in a Th2 bias. These findings indicate that OM and RM were potent adjuvant capable of directly initiating DC activation Th1 and Th2 polarization respectively.     

TGF‐β indirectly favors the development of human Th17 cells by inhibiting Th1 cells

Human Th17 clones and circulating Th17 cells showed lower susceptibility to the anti‐proliferative effect of TGF‐β than Th1 and Th2 clones or circulating Th1‐oriented T cells, respectively. Accordingly, human Th17 cells exhibited lower expression of clusterin, and higher Bcl‐2 expression and reduced apoptosis in the presence of TGF‐β, in comparison with Th1 cells. Umbilical cord blood naïve CD161⁺CD4⁺ T cells, which contain the precursors of human Th17 cells, differentiated into IL‐17A‐producing cells only in response to IL‐1β plus IL‐23, even in serum‐free cultures. TGF‐β had no effect on constitutive RORγt expression by umbilical cord blood CD161⁺ T cells but it increased the relative proportions of CD161⁺ T cells differentiating into Th17 cells in response to IL‐1β plus IL‐23, whereas under the same conditions it inhibited both T‐bet expression and Th1 development. These data suggest that TGF‐β is not critical for the differentiation of human Th17 cells, but indirectly favors their expansion because Th17 cells are poorly susceptible to its suppressive effects.     

Differentiation Imbalance of Th1/ Th17 in Peripheral Blood Mononuclear Cells Might Contribute to Pathogenesis of Hashimoto’s Thyroiditis

T helper 17(Th17) cell is a new subset of CD4⁺ T cells that produce a proinflammatory cytokine interleukin‐17 (IL‐17). Th17 cells have recently been shown to play a critical role in many autoimmune diseases that had previously been thought to be Th1 dominant. Although Hashimoto’s thyroiditis (HT) was thought to be a Th1‐type disease, the contributions of Th17 cells to the pathogenesis remain unclear. In this study, we investigated the expression levels of Th1/Th17 cell‐associated factors in peripheral blood mononuclear cells (PBMC) and plasma from patients with HT by quantitative real‐time polymerase chain reaction (RT‐qPCR) and enzyme‐linked immunosorbent assay (ELISA). Our results showed that the expression levels of Th1 cells‐related T‐bet and interferon‐γ (IFN‐γ) mRNA in PBMC from HT significantly decreased. However, the mRNA of Th17 coherent retinoic acid‐related orphan nuclear receptor gamma t (RORγt) and IL‐17 in patients with HT increased. In addition, a negative correlation between T‐bet and RORγt mRNA expression was found in patients with HT, and the similar phenomena also appeared on the levels of mRNA and plasma concentration between IFN‐γ and IL‐17. It suggested that Th17 cells rather than Th1 cells predominated among patients suffering from HT, and Th17 cells might be involved in the pathogenesis of HT.     

Reverse plasticity: TGF‐β and IL‐6 induce Th1‐to‐Th17‐cell transdifferentiation in the gut

Th17 cells are a heterogeneous population of pro‐inflammatory T cells that have been shown to mediate immune responses against intestinal bacteria. Th17 cells are highly plastic and can transdifferentiate to Th1/17 cells or unconventional Th1 cells, which are highly pathogenic in animal models of immune‐mediated diseases such as inflammatory bowel diseases. A recent European Journal of Immunology article by Liu et al. (Eur. J. Immunol. 2015. 45:1010–1018) showed, surprisingly, that Th1 cells have a similar plasticity, and could transdifferentiate to Th17 cells. Thus, IFN‐γ‐producing Th1 effector cells specific for an intestinal microbial antigen were shown to acquire IL‐17‐producing capacities in the gut in a mouse model of colitis, and in response to TGF‐β and IL‐6 in vitro. TGF‐β induced Runx1, and together with IL‐6 was shown to render the ROR‐γt and IL‐17 promoters in Th1 cells accessible for Runx1 binding. In this commentary, we discuss how this unexpected plasticity of Th1 cells challenges our view on the generation of Th1/17 cells with the capacity to co‐produce IL‐17 and IFN‐γ, and consider possible implications of this Th1‐to‐Th17‐cell conversion for therapies of inflammatory bowel diseases and protective immune responses against intracellular pathogens.     

Coincident diabetes mellitus modulates Th1‐, Th2‐, and Th17‐cell responses in latent tuberculosis in an IL‐10‐ and TGF‐β‐dependent manner

Type 2 diabetes mellitus (DM) is a risk factor for the development of active tuberculosis (TB), although its role in the TB‐induced responses in latent TB (LTB) is not well understood. Since Th1, Th2, and Th17 responses are important in immunity to LTB, we postulated that coincident DM could alter the function of these CD4⁺ T‐cell subsets. To this end, we examined mycobacteria‐induced immune responses in the whole blood of individuals with LTB‐DM and compared them with responses of individuals without DM (LTB‐NDM). T‐cell responses from LTB‐DM are characterized by diminished frequencies of mono‐ and dual‐functional CD4⁺ Th1, Th2, and Th17 cells at baseline and following stimulation with mycobacterial antigens‐purified protein derivative, early secreted antigen‐6, and culture filtrate protein‐10. This modulation was at least partially dependent on IL‐10 and TGF‐β, since neutralization of either cytokine resulted in significantly increased frequencies of Th1 and Th2 cells but not Th17 cells in LTB‐DM but not LTB individuals. LTB‐DM is therefore characterized by diminished frequencies of Th1, Th2, and Th17 cells, indicating that DM alters the immune response in latent TB leading to a suboptimal induction of protective CD4⁺ T‐cell responses, thereby providing a potential mechanism for increased susceptibility to active disease.     

IL‐23 Activated γδ T Cells Affect Th17 Cells and Regulatory T Cells by Secreting IL‐21 in Children with Primary Nephrotic Syndrome

This study (1) analysed the percentage of γδ T cells, γδ T cell subsets, Th17 cells and regulatory T cells (Treg cells) and (2) determined the role of IL ‐23 in primary nephrotic syndrome (PNS ) patients with active disease and in remission. Eighty‐four patients with PNS and 51 healthy age‐matched controls were included in this study. The percentage of γδ T cells, γδ T cell subsets, Th17 cells and Treg cells in peripheral blood mononuclear cells (PBMC s) were analysed by fluorescence‐activated cell sorting. PMBC s from PNS patients with active disease were cultured in the presence of IL ‐23, IL ‐23 and an IL ‐23 antagonist, or IL 23 and an anti‐IL ‐21 monoclonal antibody (mA b). The percentage of γδ T cells, IL ‐23R⁺ γδ T cells and IL ‐17⁺ γδ T cells were significantly increased in PNS patients with active disease. There was a positive correlation between the percentage of γδ T cells, IL ‐23R⁺ γδ T cells, IL ‐17⁺ γδ T cells and the Th17/Treg ratio. IL ‐23 increased the percentage of γδ T cells and Th17 cells and decreased the percentage of Treg cells in PBMC s isolated from PNS patients with active disease. Anti‐IL ‐21 mA b reduced the percentage of γδ T cells and Th17 cells, but increased the percentage of Treg cells. γδ T cells, IL ‐17⁺ γδ T cells and IL ‐23R⁺ γδ T cells may be involved in the pathogenesis of paediatric PNS by modulating the balance of Th17/Treg cells. γδ T cells may cause an imbalance in Th17/Treg cells by secreting IL ‐21 in the presence of IL ‐23.     

IL‐17A produced by both γδ T and Th17 cells promotes renal fibrosis via RANTES‐mediated leukocyte infiltration after renal obstruction

IL‐17A‐producing T lymphocytes play a crucial role in inflammatory kidney diseases, but their role in renal fibrosis remains to be explored. Here, we demonstrated that up‐regulation of IL‐17A was associated with the development of obstructive kidney injury. The primary source of IL‐17A production in obstructed kidneys was infiltrating γδ T lymphocytes and CD4⁺ T cells. IL‐17A‐deficient mice were protected from myofibroblast activation and extracellular matrix deposition, leading to reduced kidney fibrosis in response to obstructive injury. Mechanistically, IL‐17A deficiency suppressed the expression of the chemokine RANTES in infiltrated CD3⁺ T cells and peritubular inflammation following renal obstruction. Administration of RANTES‐neutralizing antibody significantly reduced the accumulation of T cells and macrophages, and of collagen deposition in obstructed kidneys. Taken together, our results indicate that IL‐17A contributes significantly to the pathogenesis of renal fibrosis by regulating RANTES‐mediated inflammatory cell infiltration. Copyright © 2014 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd     

Boswellic acids reduce Th17 differentiation via blockade of IL‐1β‐mediated IRAK1 signaling

Interferon‐gamma producing CD4⁺ T (Th1) cells and IL‐17‐producing CD4⁺ T (Th17) cells are involved in the pathogenesis of several autoimmune diseases including multiple sclerosis. Therefore, the development of treatment strategies controlling the generation and expansion of these effector cells is of high interest. Frankincense, the resin from trees of the genus Boswellia, and particularly its prominent bioactive compound acetyl‐11‐keto‐β‐boswellic acid (AKBA), have potent anti‐inflammatory properties. Here, we demonstrate that AKBA is able to reduce the differentiation of human CD4⁺ T cells to Th17 cells, while slightly increasing Th2‐ and Treg‐cell differentiation. Furthermore, AKBA reduces the IL‐1β‐triggered IL‐17A release of memory Th17 cells. AKBA may affect IL‐1β signaling by preventing IL‐1 receptor‐associated kinase 1 phosphorylation and subsequently decreasing STAT3 phosphorylation at Ser727, which is required for Th17‐cell differentiation. The effects of AKBA on Th17 differentiation and IL‐17A release make the compound a good candidate for potential treatment of Th17‐driven diseases.     

HMGB1 Promotes the Differentiation of Th17 via Up‐Regulating TLR2 and IL‐23 of CD14+ Monocytes from Patients with Rheumatoid Arthritis

High‐mobility group box 1 (HMGB1) is a non‐histone nuclear protein that is released extracellulary and has been implicated in autoimmune disease. Toll‐like receptor 2 (TLR2) signalling is thought to be essential for the inflammatory response and for immune disorders. In recent studies, enhanced HMGB1 and TLR2 expressions have been found in rheumatoid arthritis (RA), respectively. The aim of this study is to explore whether HMGB1 stimulation can up‐regulate the expression of TLR2 on CD14⁺ monocytes from patients with RA and to clarify the subsequent events involving Th17 cells and Th17 cell‐associated cytokine changes. Our results showed that the frequency of CD14⁺ cells in peripheral blood mononuclear cell (PBMC) was obviously increased, and enhanced expression of TLR2 on CD14⁺ monocytes was also found in patients with RA, compared with healthy controls with statistical significance (P < 0.001). In addition, the levels of IL‐17, IL‐23 and IL‐6 in supernatants from cultured monocytes from patients and in patient’s plasma were increased, and NF‐κB, the downstream target of TLR2, also showed a marked elevation after monocytes were stimulated by HMGB1. This implies that the enhanced TLR2 pathway and Th17 cell polarization may be due to HMGB1 stimulation in rheumatoid arthritis.     

CD5 enhances Th17‐cell differentiation by regulating IFN‐γ response and RORγt localization

Mechanisms that modulate the generation of Th17 cells are incompletely understood. We report that the activation of casein kinase 2 (CK2) by CD5 is essential for the efficient generation of Th17 cells in vitro and in vivo. In our study, the CD5–CK2 signaling pathway enhanced TCR‐induced activation of AKT and promoted the differentiation of Th17 cells by two independent mechanisms: inhibition of glycogen synthase kinase 3 (GSK3) and activation of mTOR. Genetic ablation of the CD5–CK2 signaling pathway attenuated TCR‐induced AKT activation and consequently increased activity of GSK3 in Th17 cells. This resulted in increased sensitivity of Th17 cells to IFN‐γ‐mediated inhibition. In the absence of CD5‐CK2 signaling, we observed decreased activity of S6K and attenuated nuclear translocation of RORγt (ROR is retinoic acid receptor related orphan receptor). These results reveal a novel and essential function of the CD5–CK2 signaling pathway and GSK3–IFN‐γ axis in regulating Th‐cell differentiation and provide a possible means to dampen Th17‐type responses in autoimmune diseases.     

Circular RNA ITCH mediates H2O2‐induced myocardial cell apoptosis by targeting miR‐17‐5p via wnt/β‐catenin signalling pathway

Cardiovascular disease is a severe threat health worldwide, and circRNAs have been shown to be correlated with the development of cardiovascular disease. Expression of circ‐ITCH and miR‐17a‐5p was evaluated by RT‐qPCR. Cell viability was measured using CCK‐8. Flow cytometry was applied to measure apoptosis rate. Binding between miR‐17‐5p and circ‐ITCH was detected via luciferase reporter assays. Levels of ATP in cells were examined with ATP testing. Western blot was used to evaluate apoptosis‐related proteins and proteins in Wnt/β‐catenin signalling pathway. H₂O₂ induced apoptosis of H9c2 cells and lowered cell viability as well as ATP levels and circ‐ITCH expression. After overexpression, circ‐ITCH enhanced cell viability and ATP concentration. Meanwhile, apoptosis was inhibited. MiR‐17‐5p was the target of circ‐ITCH as evidenced by luciferase report assays, with higher expression in H₂O₂‐induced H9c2 cells. Knockdown of miR‐17‐5p could promote cell viability and level of ATP and curb apoptosis and p53 and PARP expression. Moreover, overexpressed miR‐17‐5p could reverse the function of upregulated circ‐ITCH. Wnt3a, Wnt5a and β‐catenin in Wnt/β‐catenin signalling pathway were increased after H₂O₂ induction. Suppression of Wnt/β‐catenin signalling pathway could initiate the process of injury in H9c2 cells. Circ‐ITCH could protect myocardial cells from injuries caused by H₂O₂ by suppressing apoptosis while miR‐17‐5p played a reverse role, which could upregulate apoptosis and inhibit cell viability via Wnt/β‐catenin signalling pathway.