Human Th17 Cells Research Articles

FC03 T17 polarization of skin-homing (CLA-positive) T cells is maintained by activation-dependent, AP-1-mediated chromatin remodelling

Abstract Background T cells undergo polyclonal expansion in psoriasis and PsA, with persistence of ‘driver clones’ after effective treatment (JCI 127:4031; JI 172:1935). A recent study found roughly equally sized compartments of clonally expanded and polyclonal Th17 and Tc17 cells in psoriasis (Science 371:364). Memory T17 cells undergo monocyte-dependent expansion in CD3/CD28-activated PBMC cultures (PNAS 104:17034; JID 139:1245). Methods We stimulated PBMC from 85 psoriatic and 68 controls for 1 day with anti-CD3/CD28 Dynabeads (24 h), or without beads (0 h), followed on Day 0 or Day 1 by flow sorting (CD3+CD45RO+, CD4/CD8 × CLA+/CLA- × 0/24 h), RNA-seq and ATAC-seq. Results CD3/CD28 activation provoked marked (>100-fold) upregulation of the T17 signature transcripts IL17A, IL17F, IL22, and CCL22, and of the T1 signature transcript IFNG. However, stratified analysis of CLAP vs. CLAN in activated T cells revealed 2.9- to 12.1-fold upregulation of the four T17 signature mRNAs, without a corresponding increase in IFNG. Notably, IL17A and IL17F were overexpressed in activated T cells from psoriatic vs. control donors (each 1.9-fold, P = 4.7E−4). Occupancy analysis of 702 transcription factor (TF) motifs using CENTIPEDE revealed remarkable correlations between activation (CLAN at 24 vs. 0 h) and skin-homing status (CLAP vs. CLAN at 0 h) [Spearman’s rho = 0.94 for CD4 and 0.93 for CD8; rho(expected)∼0.5]. Compared with CLAP/CLAN, correlations with activation were much weaker for CD8/CD4, the other dimension in our 2 × 2 × 2 study design (rho = 0.41 for CLAN and 0.29 for CLAP). AP-1 motifs were significantly enriched among CLAP vs. CLAN differentially occupied motifs (P < 2.2E−16 for CD4 and CD8, Fisher’s exact). Discussion CLAP are effector memory T cells (Tem) arising after injury/infection of skin (or tonsils), whereas CLAN are central memory T cells (Tcm) that may arise in the skin, lung, or gut (JID 130:362; STM 7:269). Our results support findings that human Th17 cells are long-lived Tem (STM 3:104) and that Tem are more responsive than Tcm due to increased TF occupancy driven by AP-1 TFs (Commun Biol 6:363). Our results nominate repetitive activation of memory T cells (whether clonally via TCR activation or polyclonally via cytokines) as a mechanism for increased responsiveness of CLAP/Tem vs. CLAN/Tcm. They also advance a plausible explanation for the presence of polyclonal T cells in psoriasis lesions (‘chromatin memory’ of secondarily activated T cells), suggesting a molecular basis of the Koebner phenomenon (heterologous activation of poised chromatin, Nature 580:475), and provide a rationale for implementing highly effective treatment early in the course of psoriasis (to prevent expansion of memory T cells, clonal or not, with chromatin poised for T17 reactivation).

Inborn errors of immunity reveal the molecular requirements for the generation and maintenance of human IL-9 expressing cells.

CD4+ T cells play essential roles in adaptive immunity. Distinct CD4+ T cell subsets - Th1, Th2, Th17, Th22, T follicular helper and regulatory T cells - have been identified and their contributions to host defence and immune regulation are increasingly well-defined. IL-9 producing Th9 cells were first described in 2008 and appear to play both protective and pathogenic roles in human immunity. However, key requirements for generating human Th9 cells remain incompletely defined. Define signalling pathways that regulate IL-9 production by human CD4+ T cells. Human naive and memory CD4+ T cells were cultured under different conditions and the molecular mechanisms regulating IL-9 induction were determined by assessing the ability of CD4+ T cells from a broad range of patients (n=92) with pathogenic variants in key immune genes (n=21) to differentiate into IL-9+ cells. We identified two culture conditions that yielded IL-9-expressing cells from naïve CD4+ T cells, and amplified IL-9 production by in vivo-generated memory CD4+ T cells: TGFβ plus IL-4 (i.e. Th9 polarising condition), and the combination of IL-21, IL-23, IL-6, IL-1β and TGFβ (i.e. Th17 polarising condition). Combining these conditions had a synergistic effect in generating IL-9+CD4+ T cells. IL-9 induction required STAT3-activating cytokines as well as intact signalling via the TCR and STAT5. Importantly, IL-9 induction was restrained by IFNγ/STAT1 and IL-10. Our findings revealed critical molecules involved in inducing/restraining IL-9 production by human CD4+ T cells, thereby identifying pathways that could be targeted to modulate IL-9 in health and disease.

High-CBD Extract (CBD-X) in Asthma Management: Reducing Th2-Driven Cytokine Secretion and Neutrophil/Eosinophil Activity.

Asthma is a chronic inflammatory disorder of the airways affecting over 10% of the global population. It is characterized by airway inflammation, mucus hypersecretion, and bronchial hyperresponsiveness, driven predominantly by type 2 helper T cells (Th2) and type 2 innate lymphoid cells (ILC2s) in a subset of patients. However, a significant portion of asthmatic individuals present with "type 2-low" asthma that is often refractory to standard inhaled corticosteroid (ICS) therapy. Therefore, developing innovative therapeutic strategies has become essential. Recent studies have highlighted cannabidiol (CBD) as a promising anti-inflammatory agent capable of modulating immune responses. This study investigates the therapeutic potential of a high-CBD extract (CBD-X) in asthma. We evaluated the effects of CBD-X on cells involved in asthma pathogenesis using primary human Th2 cells, neutrophils, and asthma mouse model. Our findings indicate that CBD-X extract inhibits Th2 differentiation and reduces the secretion of IL-5 and IL-13, which are crucial cytokines in asthma. Additionally, CBD-X significantly reduces pro-inflammatory cytokines IL-8 and IL-6 in neutrophils and impairs their migration, a critical step in airway inflammation. In a murine asthma model, CBD-X administration led to marked downregulation of IgE and pro-asthmatic cytokines, along with reduced leukocyte, eosinophil, and neutrophil infiltration in lung tissues. These results suggest that CBD-X extract could offer a novel and complementary approach to managing both type 2-high and type 2-low asthma by targeting key inflammatory pathways and modulating immune cell behavior.

Fatty acid metabolism constrains Th9 cell differentiation and antitumor immunity via the modulation of retinoic acid receptor signaling

T helper 9 (Th9) cells are interleukin 9 (IL-9)-producing cells that have diverse functions ranging from antitumor immune responses to allergic inflammation. Th9 cells differentiate from naïve CD4+ T cells in the presence of IL-4 and transforming growth factor-beta (TGF-β); however, our understanding of the molecular basis of their differentiation remains incomplete. Previously, we reported that the differentiation of another subset of TGF-β–driven T helper cells, Th17 cells, is highly dependent on de novo lipid biosynthesis. On the basis of these findings, we hypothesized that lipid metabolism may also be important for Th9 cell differentiation. We therefore investigated the differentiation and function of mouse and human Th9 cells in vitro under conditions of pharmacologically or genetically induced deficiency of the intracellular fatty acid content and in vivo in mice genetically deficient in acetyl-CoA carboxylase 1 (ACC1), an important enzyme for fatty acid biosynthesis. Both the inhibition of de novo fatty acid biosynthesis and the deprivation of environmental lipids augmented differentiation and IL-9 production in mouse and human Th9 cells. Mechanistic studies revealed that the increase in Th9 cell differentiation was mediated by the retinoic acid receptor and the TGF-β–SMAD signaling pathways. Upon adoptive transfer, ACC1-inhibited Th9 cells suppressed tumor growth in murine models of melanoma and adenocarcinoma. Together, our findings highlight a novel role of fatty acid metabolism in controlling the differentiation and in vivo functions of Th9 cells.

Calcitriol Impairs the Secretion of IL-4 and IL-13 in Th2 Cells via Modulating the VDR-Gata3-Gfi1 Axis.

Calcitriol, the bioactive form of vitamin D, exerts its biological functions by binding to its cognate receptor, the vitamin D receptor (VDR). The indicators of the severity of allergies and asthma have been linked to low vitamin D levels. However, the role of calcitriol in regulating IL-4 and IL-13, two cytokines pivotal to allergic inflammation, remained unclear. Our study observed diminished IL-4 and IL-13 secretion in murine and human Th2 cells treated with calcitriol. In murine Th2 cells, Gata3 expression was attenuated by calcitriol. However, the expression of the transcriptional repressor Gfi1, too, was attenuated in the presence of calcitriol. Ectopic expression of either Gfi1 or VDR impaired the secretion of IL-13 in Th2 cells. In murine Th2 cells, VDR interacted with Gata3 but not Gfi1. Gfi1 significantly impaired Il13 promoter activation, which calcitriol failed to restore. Conversely, calcitriol augmented Gfi1 recruitment to the Il13 promoter. Ecr, a conserved region between these two genes, which enhanced the transactivation of Il4 and Il13 promoters, is essential for calcitriol-mediated suppression of both the genes. Calcitriol augmented the recruitment of VDR to the Il13 promoter and Ecr regions. Gata3 recruitment was significantly impaired at the Il13 and Ecr loci in the presence of calcitriol but increased at the Il4 promoter. Furthermore, the recruitment of the histone deacetylase HDAC1 was universally increased at the promoters of Il4, Il13, and Ecr when calcitriol was present. Together, our data clearly elucidate that calcitriol modulates VDR, Gata3, and Gfi1 to suppress IL-4 and IL-13 production in Th2 cells.

NRF2 is a spatiotemporal metabolic hub essential for the polyfunctionality of Th2 cells

Upon encountering allergens, CD4+ T cells differentiate into IL-4-producing Th2 cells in lymph nodes, which later transform into polyfunctional Th2 cells producing IL-5 and IL-13 in inflamed tissues. However, the precise mechanism underlying their polyfunctionality remains elusive. In this study, we elucidate the pivotal role of NRF2 in polyfunctional Th2 cells in murine models of allergic asthma and in human Th2 cells. We found that an increase in reactive oxygen species (ROS) in immune cells infiltrating the lungs is necessary for the development of eosinophilic asthma and polyfunctional Th2 cells in vivo. Deletion of the ROS sensor NRF2 specifically in T cells, but not in dendritic cells, significantly abolished eosinophilia and polyfunctional Th2 cells in the airway. Mechanistically, NRF2 intrinsic to T cells is essential for inducing optimal oxidative phosphorylation and glycolysis capacity, thereby driving Th2 cell polyfunctionality independently of IL-33, partially by inducing PPARγ. Treatment with an NRF2 inhibitor leads to a substantial decrease in polyfunctional Th2 cells and subsequent eosinophilia in mice and a reduction in the production of Th2 cytokines from peripheral blood mononuclear cells in asthmatic patients. These findings highlight the critical role of Nrf2 as a spatial and temporal metabolic hub that is essential for polyfunctional Th2 cells, suggesting potential therapeutic implications for allergic diseases.

The stimulation of TH2 cells results in increased IL-5 and IL-13 production via the H4 receptor.

Atopic dermatitis (AD) is a chronic inflammatory skin disease resulting in decreased quality of life. Histamine and specifically the H4 receptor play a key role in the inflammatory process in AD and serve as targets for novel therapeutic approaches. In the present study we aimed to elucidate the immunopathological mechanisms with which the H4 receptor impacts TH2 cells and contributes to AD pathophysiology. Total CD4+ T cells obtained from healthy or AD individuals and invitro differentiated TH2 cells were cultured under different conditions and the mRNA expression or protein production of target molecules were determined using quantitative real-time PCR and ELISA. H4 receptor mRNA expression was upregulated concentration dependent upon IL-4 stimulation in invitro differentiated TH2 cells progressively during the differentiation. Transcriptomic analysis of invitro differentiated TH2 versus TH1 cells revealed that the H4 receptor among other genes represents one of the highly upregulated genes in TH2 cells. Most importantly, increased amounts of IL-5 and IL-13 mRNA expression were detected in invitro differentiated TH2 cells as well as protein secretion in the presence of histamine or of the H4 receptor-selective-agonist when compared to the untreated control. We show for the first time an H4 receptor dependent upregulation of the pro-inflammatory cytokines IL-5 and IL-13 in human TH2 cells by histamine. This suggests that the blockade of the H4 receptor may lead to downregulation of these cytokines and amelioration of AD symptoms as reported in first clinical studies.

A proximal enhancer regulates RORA expression during early human Th17 cell differentiation

Gene regulatory elements, such as enhancers, greatly influence cell identity by tuning the transcriptional activity of specific cell types. Dynamics of enhancer landscape during early human Th17 cell differentiation remains incompletely understood. Leveraging ATAC-seq-based profiling of chromatin accessibility and comprehensive analysis of key histone marks, we identified a repertoire of enhancers that potentially exert control over the fate specification of Th17 cells. We found 23 SNPs associated with autoimmune diseases within Th17-enhancers that precisely overlapped with the binding sites of transcription factors actively engaged in T-cell functions. Among the Th17-specific enhancers, we identified an enhancer in the intron of RORA and demonstrated that this enhancer positively regulates RORA transcription. Moreover, CRISPR-Cas9-mediated deletion of a transcription factor binding site-rich region within the identified RORA enhancer confirmed its role in regulating RORA transcription. These findings provide insights into the potential mechanism by which the RORA enhancer orchestrates Th17 differentiation.

RORγt inverse agonist TF-S14 inhibits Th17 cytokines and prolongs skin allograft survival in sensitized mice

Chronic antibody mediated rejection (AMR) is the major cause of solid organ graft rejection. Th17 contributes to AMR through the secretion of IL17A, IL21 and IL22. These cytokines promote neutrophilic infiltration, B cell proliferation and donor specific antibodies (DSAs) production. In the current study we investigated the role of Th17 in transplant sensitization. Additionally, we investigated the therapeutic potential of novel inverse agonists of the retinoic acid receptor-related orphan receptor gamma t (RORγt) in the treatment of skin allograft rejection in sensitized mice. Our results show that RORγt inverse agonists reduce cytokine production in human Th17 cells in vitro. In mice, we demonstrate that the RORγt inverse agonist TF-S14 reduces Th17 signature cytokines in vitro and in vivo and leads to blocking neutrophilic infiltration to skin allografts, inhibition of the B-cell differentiation, and the reduction of de novo IgG3 DSAs production. Finally, we show that TF-S14 prolongs the survival of a total mismatch grafts in sensitized mice. In conclusion, RORγt inverse agonists offer a therapeutic intervention through a novel mechanism to treat rejection in highly sensitized patients.

Unconventional Activation of IRE1 Enhances Th17 Responses and Promotes Airway Neutrophilia.

Heightened unfolded protein responses (UPRs) are associated with the risk for asthma, including severe asthma. Treatment-refractory severe asthma manifests a neutrophilic phenotype with T helper (Th)17 responses. However, how UPRs participate in the deregulation of Th17 cells leading to neutrophilic asthma remains elusive. This study found that the UPR sensor IRE1 is induced in the murine lung with fungal asthma and is highly expressed in Th17 cells relative to naive CD4+ T cells. Cytokine (e.g., IL-23) signals induce the IRE1-XBP1s axis in a JAK2-dependent manner. This noncanonical activation of the IRE1-XBP1s pathway promotes UPRs and cytokine secretion by both human and mouse Th17 cells. Ern1 (encoding IRE1) deficiency decreases the expression of endoplasmic reticulum stress factors and impairs the differentiation and cytokine secretion of Th17 cells. Genetic ablation of Ern1 leads to alleviated Th17 responses and airway neutrophilia in a fungal airway inflammation model. Consistently, IL-23 activates the JAK2-IRE1-XBP1s pathway invivo and enhances Th17 responses and neutrophilic infiltration into the airway. Taken together, our data indicate that IRE1, noncanonically activated by cytokine signals, promotes neutrophilic airway inflammation through the UPR-mediated secretory function of Th17 cells. The findings provide a novel insight into the fundamental understanding of IRE1 in Th17-biased TH2-low asthma.

IL23R G149R Promotes IL-23 Unresponsiveness in Human Memory Th17 Cells

IL23R G149R Promotes IL-23 Unresponsiveness in Human Memory Th17 Cells

The Dysregulated IL-23/TH17 Axis in Endometriosis Pathophysiology.

Endometriosis is a chronic inflammatory disease in which endometrial-like tissue grows ectopically, resulting in pelvic pain and infertility. IL-23 is a key contributor in the development and differentiation of TH17 cells, driving TH17 cells toward a pathogenic profile. In a variety of inflammatory and autoimmune disorders, TH17 cells secrete proinflammatory cytokines, including IL-17, contributing to disease pathophysiology. Our studies and others have implicated IL-17 and TH17 cell dysregulation in endometriosis, which is associated with disease severity. In this article, we address whether IL-23-driven TH17 cells contribute to cardinal features of lesion proliferation, vascularization, and inflammation in endometriosis using patient samples, representative cell lines, and our established mouse model of endometriosis. The results indicated dysregulated expression of key genes in the IL-23/TH17 axis in patient ectopic and eutopic endometrial samples and increased IL-23 protein in patient plasma compared with controls. In vitro studies using primary human TH cells determined that rIL-23 mixture treatment increased pathogenic TH17 cell frequency. Similarly, rIL-23 treatment of cell lines (12Z cells, EECCs, HUVECs, and hESCs) representative of the endometriotic lesion microenvironment increased cytokines and growth factors, which play a role in lesion establishment and maintenance. In a syngeneic mouse model of endometriosis, rIL-23 treatment altered numbers of myeloid and T cell subsets in peritoneal fluid and increased giant cells within the lesion. Lesions from rIL-23-treated mice did not reveal significant alterations in proliferation/vascularization, although trends of increased proliferation and vascularization were observed. Collectively, these findings provide insights into the impact of the IL-23/TH17 axis on local immune dysfunction and broadly on endometriosis pathophysiology.

Identification and pre-clinical investigation of 3-O-cyclohexanecarbonyl-11-keto-β-boswellic acid as a drug for external use to treat psoriasis.

Psoriasis vulgaris is a refractory skin inflammatory disorder with 80% of the cases belonging to the mild-to-moderate type, which can be controlled by topical treatment. Nevertheless, the drugs for external use have not been upgraded for decades. We modified acetyl-11-keto-beta-boswellic acid (ABKA), a natural compound shown to treat psoriasis animal models, to improve efficacy and solubility for topical use. Eleven compounds were synthesized using AKBA as a lead compound, and their effects on Th17 cell differentiation were screened. 3-O-cyclohexanecarbonyl-11-keto-β-boswellic acid (CKBA) potently inhibited Th17 cell differentiation. Its efficacy in a mouse model of psoriasis was assessed along with its pharmacology and safety profile when topically or systemically delivered to several animal species. CKBA inhibited mouse and human Th17 cell differentiation with an IC50 of 3.28 and 3.61 μM, respectively, and directly targeted acetyl-CoA carboxylase 1 (ACC1). Safety evaluation and toxicity tests suggested that systemically delivered high-dose CKBA for 14 days had no dose-associated adverse effects on the CNS, haematopoietic, cardiovascular, respiratory and digestive systems of cynomolgus monkeys. CKBA ointment permeated the skin and did not irritate or sensitize intact skin. CKBA ointment mediated dose-dependent suppression of imiquimod-induced psoriasis-like skin inflammation with slow absorption and limited bioavailability (<10% in rats and <1% in minipigs). CKBA is safe when topically or systemically delivered to animals. The beneficial effects of CKBA ointment in a mouse model of psoriasis indicate that this is a promising drug candidate for further development as a treatment for psoriasis.

High-parameter phenotypic characterization reveals a subset of human Th17 cells that preferentially produce IL-17 against M. tuberculosis antigen.

Interleukin-17-producing CD4 T cells contribute to the control of Mycobacterium tuberculosis (Mtb) infection in humans; whether infection with human immunodeficiency virus (HIV) disproportionately affects distinct Th17-cell subsets that respond to Mtb is incompletely defined. We performed high-definition characterization of circulating Mtb-specific Th17 cells by spectral flow cytometry in people with latent TB and treated HIV (HIV-ART). We also measured kynurenine pathway activity by liquid chromatography-mass spectrometry (LC/MS) on plasma and tested the hypothesis that tryptophan catabolism influences Th17-cell frequencies in this context. We identified two subsets of Th17 cells: subset 1 defined as CD4+Vα7.2-CD161+CD26+and subset 2 defined as CD4+Vα7.2-CCR6+CXCR3-cells of which subset 1 was significantly reduced in latent tuberculosis infection (LTBI) with HIV-ART, yet Mtb-responsive IL-17-producing CD4 T cells were preserved; we found that IL-17-producing CD4 T cells dominate the response to Mtb antigen but not cytomegalovirus (CMV) antigen or staphylococcal enterotoxin B (SEB), and tryptophan catabolism negatively correlates with both subset 1 and subset 2 Th17-cell frequencies. We found differential effects of ART-suppressed HIV on distinct subsets of Th17 cells, that IL-17-producing CD4 T cells dominate responses to Mtb but not CMV antigen or SEB, and that kynurenine pathway activity is associated with decreases of circulating Th17 cells that may contribute to tuberculosis immunity.

PIM kinases regulate early human Th17 cell differentiation

The serine/threonine-specific Moloney murine leukemia virus (PIM) kinase family (i.e., PIM1, PIM2, and PIM3) has been extensively studied in tumorigenesis. PIM kinases are downstream of several cytokine signaling pathways that drive immune-mediated diseases. Uncontrolled T helper 17 (Th17) cell activation has been associated with the pathogenesis of autoimmunity. However, the detailed molecular function of PIMs in human Th17 cell regulation has yet to be studied. In the present study, we comprehensively investigated how the three PIMs simultaneously alter transcriptional gene regulation during early human Th17 cell differentiation. By combining PIM triple knockdown with bulk and scRNA-seq approaches, we found that PIM deficiency promotes the early expression of key Th17-related genes while suppressing Th1-lineage genes. Further, PIMs modulate Th cell signaling, potentially via STAT1 and STAT3. Overall, our study highlights the inhibitory role of PIMs in human Th17 cell differentiation, thereby suggesting their association with autoimmune phenotypes.

The USP7-STAT3-granzyme-Par-1 axis regulates allergic inflammation by promoting differentiation of IL-5-producing Th2 cells.

Uncontrolled type 2 immunity by type 2 helper T (Th2) cells causes intractable allergic diseases; however, whether the interaction of CD4+ T cells shapes the pathophysiology of allergic diseases remains unclear. We identified a subset of Th2 cells that produced the serine proteases granzyme A and B early in differentiation. Granzymes cleave protease-activated receptor (Par)-1 and induce phosphorylation of p38 mitogen-activated protein kinase (MAPK), resulting in the enhanced production of IL-5 and IL-13 in both mouse and human Th2 cells. Ubiquitin-specific protease 7 (USP7) regulates IL-4-induced phosphorylation of STAT3, resulting in granzyme production during Th2 cell differentiation. Genetic deletion of Usp7 or Gzma and pharmacological blockade of granzyme B ameliorated allergic airway inflammation. Furthermore, PAR-1+ and granzyme+ Th2 cells were colocalized in nasal polyps from patients with eosinophilic chronic rhinosinusitis. Thus, the USP7-STAT3-granzymes-Par-1 pathway is a potential therapeutic target for intractable allergic diseases.

82 IL-9 sensitizes human pathogenic Th2 cells to pro-inflammatory IL-18 signals in atopic dermatitis

82 IL-9 sensitizes human pathogenic Th2 cells to pro-inflammatory IL-18 signals in atopic dermatitis

A clinically-relevant STING agonist restrains human TH17 cell inflammatory profile

The STING signaling pathway has gained attention over the last few years due to its ability to incite antimicrobial and antitumoral immunity. Conversely, in mouse models of autoimmunity such as colitis and multiple sclerosis, where TH17 cells are implicated in tissue inflammation, STING activation has been associated with the attenuation of immunogenic responses. In this line, STING was found to limit murine TH17 pro-inflammatory program in vitro. Here we demonstrate that 2′3′-c-di-AM(PS)2(Rp,Rp), a STING agonist that has been undergoing clinical trials for antitumor immunotherapy, activates the STING signalosome in differentiating human TH17 cells. Of particular interest, 2′3′-c-di-AM(PS)2(Rp,Rp) reduces IL-17A production and IL23R expression by human TH17 cells while it favors the generation of regulatory T (Treg) cells. These findings suggest that STING agonists may be promising approaches for treating human TH17-mediated chronic inflammation.

IL-21/23 axis modulates inflammatory cytokines and RANKL expression in RA CD4+ T cells via p-Akt1 signaling.

CD4+ T cells are critically involved in the pathogenesis of Rheumatoid Arthritis; an autoimmune disorder characterized by joint inflammation and bone degeneration. In this study, we focused on the critical role of cytokines, IL-21 and IL-23 in facilitating the aberrant status of RA Th17-like cells and report their significant contribution(s) in modulating the expression of inflammatory cytokines and RANKL. Blood and synovial fluid collected from a total of 167 RA patients and 25 healthy volunteers were assessed for various inflammatory markers and RANKL expression in plasma and CD4+ T cells. Subsequent ex vivo studies examined the role of specific cytokines, IL-21 and IL-23 in mediating inflammation and RANKL upregulation by blocking their expression with neutralizing antibodies in RA CD4+ T cells and terminally differentiated human Th17 cells. Further, the role of p-Akt1 as a signalling target downstream of IL-21 and IL-23 was evinced with IL-21 and IL-23 inhibition and phospho Akt-1/2 kinase inhibitor. Our observations highlighted the augmented inflammatory cytokine levels in plasma and an aberrant CD4+ T cell phenotype expressing exaggerated inflammatory cytokines and membrane RANKL expression in RA as opposed to healthy controls. Neutralization of either IL-21 or IL-23 (p19 and p40) or both, resulted in downregulation of the cytokines, TNF-α, IFN-γ and IL-17 and RANKL expression in these cells, signifying the critical role of IL-21/23 axis in modulating inflammation and RANKL. Subsequent dissection of the signaling pathway found p-Akt1 as the key phosphoprotein downstream of both IL-21 and IL-23, capable of increasing inflammatory cytokines and RANKL production. Our findings unequivocally identify IL-21/23 axis in RA CD4+ T cells as a key regulator dictating two critical processes i.e. exaggerated inflammation and higher RANKL expression and provide critical targets in their downstream signalling for therapeutic approaches.

LB1645 IL-9 sensitizes human pathogenic Th2 cells to pro-inflammatory IL-18 signals in atopic dermatitis

LB1645 IL-9 sensitizes human pathogenic Th2 cells to pro-inflammatory IL-18 signals in atopic dermatitis