Phenotypic and functional features of human Th17 cells

Behind Enemy Lines: Immunomodulatory Armamentarium of the Schistosome Parasite

The deeply rooted, intricate relationship between the Schistosoma parasite and the human host has enabled the parasite to successfully survive within the host and surreptitiously evade the host's immune attacks. The parasite has developed a variety of strategies in its immunomodulatory armamentarium to promote infection without getting harmed or killed in the battlefield of immune responses. These include the production of immunomodulatory molecules, alteration of membranes, and the promotion of granuloma formation. Schistosomiasis thus serves as a paradigm for understanding the Th2 immune responses seen in various helminthiases. This review therefore aims to summarize the immunomodulatory mechanisms of the schistosome parasites to survive inside the host. Understanding these immunomodulatory strategies not only provides information on parasite-host interactions, but also forms the basis in the development of novel drugs and vaccines against the schistosome infection, as well as various types of autoimmune and inflammatory conditions.

Role of TH17 Responses in Increasing Herpetic Keratitis in the Eyes of Mice Infected with HSV-1

Purpose

T_H17 cells play an important role in host defense and autoimmunity yet very little is known about the role of IL17 in herpes simplex virus (HSV)-1 infectivity. To better understand the relationship between IL17 and HSV-1 infection, we assessed the relative impact of IL17A-deficiency and deficiency of its receptors on HSV-1 responses in vivo.

Methods

We generated IL17RA^−/− and IL17RA^−/−RC^−/− mice in-house and infected them along with IL17A^−/− and IL17RC^−/− mice in the eyes with 2 × 10⁵ PFU/eye of wild type (WT) HSV-1 strain McKrae. WT C57BL/6 mice were used as control. Virus replication in the eye, survival, corneal scarring (CS), angiogenesis, levels of latency-reactivation, and levels of CD8 and exhaustion markers (PD1, TIM3, LAG3, CTLA4, CD244, and CD39) in the trigeminal ganglia (TG) of infected mice were determined on day 28 postinfection.

Results

No significant differences in virus replication in the eye, survival, latency, reactivation, and exhaustion markers were detected among IL17A^−/−, IL17RA^−/−, IL17RC^−/−, IL17RA^−/−RC^−/−, and WT mice. However, mice lacking IL17 had significantly less CS and angiogenesis than WT mice. In addition, angiogenesis levels in the absence of IL17RC and irrespective of the absence of IL17RA were significantly less than in IL17A- or IL17RA-deficient mice.

Conclusions

Our results suggest that the absence of IL17 protects against HSV-1-induced eye disease, but has no role in protecting against virus replication, latency, or reactivation. In addition, our data provide rationale for blocking IL17RC function rather than IL17A or IL17RA function as a key driver of HSV-1-induced eye disease.

Interleukin-17 in Chronic Inflammatory Neurological Diseases

A critical role for IL-17, a cytokine produced by T helper 17 (Th17) cells, has been indicated in the pathogenesis of chronic inflammatory and autoimmune diseases. A positive effect of blockade of IL-17 secreted by autoreactive T cells has been shown in various inflammatory diseases. Several cytokines, whose production is affected by environmental factors, control Th17 differentiation and its maintenance in tissues during chronic inflammation. The roles of IL-17 in the pathogenesis of chronic neuroinflammatory conditions, multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE), Alzheimer's disease, and ischemic brain injury are reviewed here. The role of environmental stimuli in Th17 differentiation is also summarized, highlighting the role of viral infection in the regulation of pathogenic T helper cells in EAE.

Immune Cell Trafficking to the Liver

The human liver is an organ with a diverse array of immunologic functions. Its unique anatomic position that leads to it receiving all the mesenteric venous blood, combined with its unique micro anatomy, allows it to serve as a sentinel for the body's immune system. Hepatocytes, biliary epithelial cells, Kupffer cells, stellate cells, and liver sinusoidal endothelial cells express key molecules that recruit and activate innate and adaptive immunity. Additionally, a diverse array of lymphoid and myeloid immune cells resides within and traffics to the liver in specific circumstances. Derangement of these trafficking mechanisms underlies the pathophysiology of autoimmune liver diseases, nonalcoholic steatohepatitis, and liver transplantation. Here, we review these pathways and interactions along with potential targets that have been identified to be exploited for therapeutic purposes.

The role of Th17 immunity in chronic ocular surface disorders

Th17 cells have been implicated in the pathogenesis of numerous inflammatory and autoimmune conditions. At the ocular surface, Th17 cells have been identified as key effector cells in chronic ocular surface disease. Evidence from murine studies indicates that following differentiation and expansion, Th17 cells migrate from the lymphoid tissues to the eye, where they release inflammatory cytokines including, but not limited to, their hallmark cytokine IL-17A. As the acute phase subsides, a population of long-lived memory Th17 cells persist, which predispose hosts both to chronic inflammation and severe exacerbations of disease; of great interest is the small subset of Th17/1 cells that secrete both IL-17A and IFN-γ in acute-on-chronic disease exacerbation. Over the past decade, substantial progress has been made in deciphering how Th17 cells interact with the immune and neuroimmune pathways that mediate chronic ocular surface disease. Here, we review (i) the evidence for Th17 immunity in chronic ocular surface disease, (ii) regulatory mechanisms that constrain the Th17 immune response, and (iii) novel therapeutic strategies targeting Th17 cells.

CBD Suppression of EAE Is Correlated with Early Inhibition of Splenic IFN-γ + CD8+ T Cells and Modest Inhibition of Neuroinflammation

In this study cannabidiol (CBD) was administered orally to determine its effects and mechanisms in the experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis (MS). We hypothesized that 75 mg/kg of oral CBD given for 5 days after initiation of disease would reduce EAE severity through suppression of either the early peripheral immune or late neuroimmune response. EAE was induced in C57BL/6 mice at two different magnitudes, and peripheral inflammatory and neuroinflammatory responses were measured at days 3, 10, and 18. Th1, Th17, Tc1, Tc17, Tregs, and myeloid derived suppressor cells (MDSC) were identified from the lymph nodes and spleens of each mouse to determine if CBD altered the suppressor cell or inflammatory cell populations in secondary lymphoid tissues. Additionally, neuroinflammation was identified in brain and spinal cord tissues using various immunohistochemical techniques and flow cytometry. Early treatment of EAE with oral CBD reduced clinical disease at the day 18 timepoint which correlated with a significant decrease in the percentage of MOG_35-55 specific IFN-γ producing CD8⁺ T cells in the spleen at day 10. Analysis of both T cell infiltration and lesion size within the spinal cord also showed a moderate reduction in neuroinflammation within the central nervous system (CNS). These results provide evidence that oral CBD suppressed the peripheral immune response that precedes neuroinflammation; however, analysis of the neuroinflammatory endpoints also suggest that the modest reduction in neuroinflammation was only partially responsible for CBD's neuroprotective capability. Graphical Abstract CBD was administered orally for the first 5 days following initiation of EAE. CBD attenuated clinical disease, and we found that CBD suppressed IFN-γ producing CD8⁺ T cells in the spleen at day 10. There was also modest suppression of neuroinflammation. Together these data demonstrate that early, oral administration of CBD protected mice from disease, but the modest effects on neuroinflammation suggest other mechanisms participate in CBD's neuroprotective effect in EAE.

Aberrant peripheral blood CD4+ CD25+ FOXP3+ regulatory T cells/T helper-17 number is associated with the outcome of patients with lymphoma

Little is known about the clinical significance of the peripheral blood CD4⁺ CD25⁺ FOXP3⁺ regulatory T cells (Tregs) and T helper-17 (Th17) cells in lymphoma patients. In this study, the prognostic and clinical significance of peripheral blood Tregs and Th17 cells were evaluated in lymphoma patients during different phases. The frequency of Tregs and Th17 lymphocytes was measured by flow cytometry method in 47 classical Hodgkin's lymphoma (cHL) and 48 diffuse large B cell lymphoma (DLBCL) patients. Our results showed that the frequency of Tregs and absolute Treg count was significantly reduced in relapsed patients compared to patients at the remission phase, as well as with newly diagnosed untreated patients in both groups. Patients who reached complete remission had elevated frequency of CD4⁺ FOXP3⁺ lymphocytes, Tregs, absolute Treg count, Treg/CD4 and Treg/Th17 ratio in the cHL group and CD4⁺ CD25⁺ cells in DLBCL group. The frequency of Tregs, absolute Treg count and Treg/Th17 ratio in cHL patients and CD4⁺ FOXP3⁺ and CD4⁺ CD25⁺ cells in DLBCL patients positively associated with survival rate. Moreover, the percentage of Tregs and absolute Treg count positively correlated with white blood cell, platelet count and ESR level in cHL patients and with white blood cell count in DLBCL patients. The initial number of Tregs/Th17 cells and also the Treg/Th17 ratio was not associated with changes in disease-free survival (DFS) in both groups. Therefore, higher frequency of peripheral blood Tregs and Treg/Th17 ratio might be associated with a favorable outcome in lymphoma patients, better response to chemotherapy and lower rate of relapse.

Escherichiacoli-Specific CD4+ T Cells Have Public T-Cell Receptors and Low Interleukin 10 Production in Crohn's Disease

BACKGROUND & AIMS

Crohn's disease (CD) likely represents decreased immune tolerance to intestinal bacterial antigens. Most CD patients have high titers of antibodies to intestinal commensal proteins, including the outer membrane porin C (OmpC) of Escherichia coli.

METHODS

By using major histocompatibility complex II tetramers, we identified an HLA-DRB1∗15:01-restricted peptide epitope of OmpC recognized by CD4+ T cells in peripheral blood mononuclear cells from HLA-DRB1∗15:01+ healthy control (HC) and CD patients.

RESULTS

The precursor frequency of these cells in CD correlated with anti-OmpC IgA titers, but did not differ from that of HCs. In both cohorts, they showed a CD161+, integrin α4β7+ phenotype ex vivo by flow cytometry, distinct from the C-X-C Motif Chemokine Receptor 3 phenotype of autologous influenza hemagglutinin (Flu) peptide-specific T cells. The T-cell receptor α and β chains of in vitro-expanded OmpC-specific T-cell clones often contained public amino acid sequences that were identical in cells from different patients. Expanded T-cell clones from CD subjects produced significantly less interleukin (IL)10 (P < .0001) than those from HCs, and a trend toward decreased production of the T helper 2 cell-associated IL4, IL5, and IL13 by CD clones also was seen.

CONCLUSIONS

Both HCs and CD patients have detectable OmpC-specific T cells in circulation, with similar immunophenotypes and often identical T-cell-receptor sequences. However, expanded clones from patients with CD produce less of the immunoregulatory cytokine IL10, showing a selective defect in the regulatory function of intestinal microbial antigen-specific T cells in patients with CD.

Immune complex disease in a chronic monkey study with a humanised, therapeutic antibody against CCL20 is associated with complement-containing drug aggregates

Despite the potential for the chemokine class as therapeutic targets in immune mediated disease, success has been limited. Many chemokines can bind to multiple receptors and many receptors have multiple ligands, with few exceptions. One of those exceptions is CCL20, which exclusively pairs to CCR6 and is associated with several immunologic conditions, thus providing a promising therapeutic target. Following successful evaluation in a single dose, first time in human clinical study, GSK3050002—a humanized IgG1 monoclonal antibody against human CCL20—was evaluated in a 26-week cynomolgus monkey toxicology study. A high incidence of unexpected vascular and organ inflammation was observed microscopically, leading to the decision to halt clinical development. Here we report a dose-responsive increase in the incidence and severity of inflammation in multiple organs from monkeys receiving 30 and 300 mg/kg/week by either subcutaneous or intravenous injection. Histomorphological changes resembled an immune complex-mediated pathology, which is often due to formation of anti-drug antibodies in monkeys receiving a human protein therapeutic and thus not predictive of clinical outcome. However, the presentation was atypical in that there was a clear dose response with a very high incidence of inflammation with a low incidence of ADA that did not correlate well individually. Additionally, the immunohistologic presentation was atypical in that the severity and distribution of tissue inflammation was greater than the numbers of associated immune complexes (i.e., granular deposits). An extensive ex vivo analysis of large molecular weight protein complexes in monkey serum from this study and in human serum samples demonstrated a time-dependent aggregation of GSK3050002, that was not predicted by in vitro assays. The aggregates also contained complement components. These findings support the hypothesis that immune complexes of drug aggregates, not necessarily including anti-drug antibodies, can fix complement, accumulate over time, and trigger immune complex disease. A situation which may have increased clinical relevance than typical anti-drug antibody-associated immune complex disease in monkeys administered human antibody proteins.

Transient Expression of IL-17A in Foxp3 Fate-Tracked Cells in Porphyromonas gingivalis-Mediated Oral Dysbiosis

In periodontitis Porphyromonas gingivalis contributes to the development of a dysbiotic oral microbiome. This altered ecosystem elicits a diverse innate and adaptive immune response that simultaneously involves Th1, Th17, and Treg cells. It has been shown that Th17 cells can alter their gene expression to produce interferon-gamma (IFN-γ). Forkhead box P3 (Foxp3) is considered the master regulator of Treg cells that produce inhibitory cytokines like IL-10. Differentiation pathways that lead to Th17 and Treg cells from naïve progenitors are considered antagonistic. However, it has been reported that Treg cells expressing IL-17A as well as IFN-γ producing Th17 cells have been observed in several inflammatory conditions. Each scenario appears plausible with T cell transdifferentiation resulting from persistent microbial challenge and consequent inflammation. We established that oral colonization with P. gingivalis drives an initial IL-17A dominated Th17 response in the oral mucosa that is dependent on intraepithelial Langerhans cells (LCs). We hypothesized that Treg cells contribute to this initial IL-17A response through transient expression of IL-17A and that persistent mucosal colonization with P. gingivalis drives Th17 cells toward an IFN-γ phenotype at later stages of infection. We utilized fate-tracking mice where IL-17A- or Foxp3-promoter activity drives the permanent expression of red fluorescent protein tdTomato to test our hypothesis. At day 28 of infection timeline, Th17 cells dominated in the oral mucosa, outnumbering Th1 cells by 3:1. By day 48 this dominance was inverted with Th1 cells outnumbering Th17 cells by nearly 2:1. Tracking tdTomato⁺ Th17 cells revealed only sporadic transdifferentiation to an IFN-γ-producing phenotype by day 48; the appearance of Th1 cells at day 48 was due to a late de novo Th1 response. tdTomato⁺ Foxp3⁺ T cells were 35% of the total live CD4⁺T cells in the oral mucosa and 3.9% of them developed a transient IL-17A-producing phenotype by day 28. Interestingly, by day 48 these IL-17A-producing Foxp3⁺ T cells had disappeared. Therefore, persistent oral P. gingivalis infection stimulates an initial IL-17A-biased response led by Th17 cells and a small but significant number of IL-17A-expressing Treg cells that changes into a late de novo Th1 response with only sporadic transdifferentiation of Th17 cells.

Traitor or warrior-Treg cells sneaking into the lesions of psoriatic arthritis

Regulatory T (Treg) cells have been recognized to maintain immune tolerance, which contributes to prevention of autoimmune diseases. However, recent evidence has demonstrated different characteristics of these cells between those that are in circulation compared to those in various local tissues. In addition, the ability of Treg cells to have plasticity in certain disease settings and in inflammatory lesions has been increasingly recognized. Herein we summarize updated knowledge of Treg biology and discuss the current understanding of tissue-resident Treg cells in psoriatic arthritis (PsA), attempting to provide new insights into precise role of Treg cells in the immune response and as a possible therapeutic intervention in patients with PsA.

Discovery of [1,2,4]Triazolo[1,5-a]pyridine Derivatives as Potent and Orally Bioavailable RORγt Inverse Agonists

The retinoic acid receptor-related orphan nuclear receptor γt (RORγt), a promising therapeutic target, is a major transcription factor of genes related to psoriasis pathogenesis such as interleukin (IL)-17A, IL-22, and IL-23R. On the basis of the X-ray cocrystal structure of RORγt with 1a, an analogue of the known piperazine RORγt inverse agonist 1, triazolopyridine derivatives of 1 were designed and synthesized, and analogue 3a was found to be a potent RORγt inverse agonist. Structure-activity relationship studies on 3a, focusing on the treatment of its metabolically unstable cyclopentyl ring and the central piperazine core, led to a novel analogue, namely, 6-methyl-N-(7-methyl-8-(((2S,4S)-2-methyl-1-(4,4,4-trifluoro-3-(trifluoromethyl)butanoyl)piperidin-4-yl)oxy)[1,2,4]triazolo[1,5-a]pyridin-6-yl)nicotinamide (5a), which exhibited strong RORγt inhibitory activity and a favorable pharmacokinetic profile. Moreover, the in vitro and in vivo evaluation of 5a in a human whole-blood assay and a mouse IL-18/23-induced cytokine expression model revealed its robust and dose-dependent inhibitory effect on IL-17A production.

Molecular mechanisms underlying prostaglandin E2-exacerbated inflammation and immune diseases

Prostaglandins (PGs) are the major lipid mediators in animals and which are biosynthesized from arachidonic acid by the cyclooxygenases (COX-1 or COX-2) as the rate-limiting enzymes. Prostaglandin E2 (PGE2), which is the most abundantly detected PG in various tissues, exerts versatile physiological and pathological actions via four receptor subtypes (EP1-4). Non-steroidal anti-inflammatory drugs, such as aspirin and indomethacin, exert potent anti-inflammatory actions by the inhibition of COX activity and the resulting suppression of PG production. Therefore, PGE2 has been shown to exacerbate several inflammatory responses and immune diseases. Recently, studies using mice deficient in each PG receptor subtype have clarified the detailed mechanisms underlying PGE2-associated inflammation and autoimmune diseases involving each EP receptor. Here, we review the recent advances in our understanding of the roles of PGE2 receptors in the progression of acute and chronic inflammation and autoimmune diseases. PGE2 induces acute inflammation through mast cell activation via the EP3 receptor. PGE2 also induces chronic inflammation and various autoimmune diseases through T helper 1 (Th1)-cell differentiation, Th17-cell proliferation and IL-22 production from Th22 cells via the EP2 and EP4 receptors. The possibility of EP receptor-targeted drug development for the treatment of immune diseases is also discussed.

Systemic Th17 response in the presence of periodontal inflammation

The relationship between periodontitis and the pathogenesis of other inflammatory diseases, such as diabetes, rheumatoid arthritis and obesity has been an important topic of study in recent decades. The Th17 pathway plays a significant role in how local inflammation can influence systemic inflammation in the absence of systemic pathology.

Single-Cell Protein and RNA Expression Analysis of Mononuclear Phagocytes in Intestinal Mucosa and Mesenteric Lymph Nodes of Ulcerative Colitis and Crohn's Disease Patients

Inflammatory bowel diseases (IBDs), which include Crohn's disease (CD) and ulcerative colitis (UC), are driven by an abnormal immune response to commensal microbiota in genetically susceptible hosts. In addition to epithelial and stromal cells, innate and adaptive immune systems are both involved in IBD immunopathogenesis. Given the advances driven by single-cell technologies, we here reviewed the immune landscape and function of mononuclear phagocytes in inflamed non-lymphoid and lymphoid tissues of CD and UC patients. Immune cell profiling of IBD tissues using scRNA sequencing combined with multi-color cytometry analysis identifies unique clusters of monocyte-like cells, macrophages, and dendritic cells. These clusters reflect either distinct cell lineages (nature), or distinct or intermediate cell types with identical ontogeny, adapting their phenotype and function to the surrounding milieu (nurture and tissue imprinting). These advanced technologies will provide an unprecedented view of immune cell networks in health and disease, and thus may offer a personalized medicine approach to patients with IBD.

Evidence for a pathogenic role of extrafollicular, IL-10-producing CCR6+B helper T cells in systemic lupus erythematosus

Interleukin 10 (IL-10) is an antiinflammatory cytokine, but also promotes B cell responses and plays a pathogenic role in systemic lupus erythematosus (SLE). CD4⁺CCR6⁺IL-7R⁺T cells from human tonsils produced IL-10 following stimulation by naïve B cells, which promoted B cell immunoglobulin G (IgG) production. These tonsillar CCR6⁺B helper T cells were phenotypically distinct from follicular helper T (T_FH) cells and lacked BCL6 expression. In peripheral blood, a CCR6⁺T cell population with similar characteristics was identified, which lacked Th17- and T_FH-associated gene signatures and differentiation-associated surface markers. CD4⁺CCR6⁺T cells expressing IL-10, but not IL-17, were also detectable in the spleens of cytokine reporter mice. They provided help for IgG production in vivo, and expanded systemically in pristane-induced lupus-like disease. In SLE patients, CD4⁺CCR6⁺IL-7R⁺T cells were associated with the presence of pathogenic anti-dsDNA (double-stranded DNA) antibodies, and provided spontaneous help for autoantibody production ex vivo. Strikingly, IL-10-producing CCR6⁺T cells were highly abundant in lymph nodes of SLE patients, and colocalized with B cells at the margins of follicles. In conclusion, we identified a previously uncharacterized population of extrafollicular B helper T cells, which produced IL-10 and could play a prominent pathogenic role in SLE.

Lymphocyte Activation Gene (LAG)-3 Is Associated With Mucosal Inflammation and Disease Activity in Ulcerative Colitis

BACKGROUND AND AIMS

Lymphocyte activation gene [LAG]-3 is an immune checkpoint and its expression identifies recently activated lymphocytes that may contribute to inflammation. We investigated the role of LAG-3 by analysing its expression and function in immune cells from blood and tissue of patients with ulcerative colitis [UC].

METHODS

The phenotypic properties of LAG-3+ T cells were determined by flow cytometry, qRT-PCR and single-cell RNA-sequencing. LAG-3+ cells were quantified and correlated with disease activity. The functional effects of LAG-3+ cells were tested using a depleting anti-LAG-3 monoclonal antibody [mAb] in a mixed lymphocyte reaction [MLR].

RESULTS

LAG-3+ cells in the blood were negligible. LAG-3+ lymphocytes were markedly increased in inflamed mucosal tissue and both frequencies of LAG-3+ T cells and transcript levels of LAG3 correlated with endoscopic severity. LAG-3 expression was predominantly on effector memory T cells, and single-cell RNA-sequencing revealed LAG3 expression in activated and cytokine-producing T cell subsets. Foxp3+CD25hi Tregs also expressed LAG-3, although most mucosal Tregs were LAG-3-. Mucosal LAG-3+ cells produced mainly interferon γ [IFNγ] and interleukin-17A. LAG-3+ cell numbers decreased in patients who responded to biologics, and remained elevated in non-responders. Treatment with a depleting anti-LAG-3 mAb led to a reduction in proliferation and IFNγ production in an MLR.

CONCLUSIONS

LAG-3+ cells are increased in the inflamed mucosa, predominantly on effector memory T cells with an activated phenotype and their cell numbers positively correlate with disease activity. Depleting LAG-3 eliminates activated proliferating T cells, and hence LAG-3 could be a therapeutic target in UC.

A molecular network regulating the proinflammatory phenotype of human memory T lymphocytes

Understanding the mechanisms that modulate helper T lymphocyte functions is crucial to decipher normal and pathogenic immune responses in humans. To identify molecular determinants influencing the pathogenicity of T cells, we separated ex vivo-isolated primary human memory T lymphocytes on the basis of their ability to produce high levels of inflammatory cytokines. We found that the inflammatory, cytokine-producing phenotype of memory T lymphocytes was defined by a specific core gene signature and was mechanistically regulated by the constitutive activation of the NF-κB pathway and by the expression of the transcriptional repressor BHLHE40. BHLHE40 attenuated the expression of anti-inflammatory factors, including miR-146a, a negative regulator of NF-κB activation and ZC3H12D, an RNase of the Regnase-1 family able to degrade inflammatory transcripts. Our data reveal a molecular network regulating the proinflammatory phenotype of human memory T lymphocytes, with the potential to contribute to disease.

Transcriptomic Analysis and High-dimensional Phenotypic Mapping of Mononuclear Phagocytes in Mesenteric Lymph Nodes Reveal Differences Between Ulcerative Colitis and Crohn's Disease

BACKGROUND AND AIMS

Crohn's disease [CD] and ulcerative colitis [UC] are distinct forms of inflammatory bowel disease. Heterogeneity of HLA-DR+SIRPα + mononuclear phagocytes [MNPs], including macrophages [MΦ], monocyte-derived [Mono] cells, and dendritic cells [DCs], was reported in gut tissue but not yet investigated in mesenteric lymph nodes [MLNs] of IBD patients. We here compared the phenotype, function, and molecular profile of HLA-DR+SIRPα + MNPs in CD and UC MLNs.

METHODS

Cell distribution, morphology, immune function, and transcriptomic [bulk RNAseq] and high-dimensional protein expression profiles [CyTOF] of HLA-DR+SIRPα + MNPs were examined in MLNs of UC [n = 14], CD [n = 35], and non-IBD [n = 12] patients.

RESULTS

Elevated frequencies of CD14+CD64+CD163+ [Mono/MΦ-like] MNPs displaying monocyte/MΦ morphology and phagocytic function were a distinct feature of UC MLNs. In CD, the proportion of CD14-CD64-CD163- [DC-like] cells was augmented relative to Mono/MΦ-like cells; DC-like cells drove naïve T cell proliferation, Th1 polarisation, and Th17 TCM plasticity. Gene expression profile corroborated the nature of DC-like cells, best represented by BTLA, SERPINF, IGJ and, of Mono/MΦ-like cells, defined by CD163, MARCO, MAFB, CD300E, S100A9 expression. CyTOF analysis showed that CD123+ plasmacytoid cells predominated over conventional DCs in DC-like cells. Four CD163+ clusters were revealed in Mono/MΦ-like cells, two of which were enriched in MARCO-CD68dimHLA-DRdim monocyte-like cells and MARCOhiCD68hiHLA-DRhi Mɸ, whose proportion increased in UC relative to CD.

CONCLUSIONS

Defining the landscape of MNPs in MLNs provided evidence for expansion of CD163+ Mono/MΦ-like cells in UC only, highlighting a distinction between UC and CD, and thus the potential contribution of monocyte-like cells in driving colitis.

IFN-γ and IL-17A regulate intestinal crypt production of CXCL10 in the healthy and inflamed colon

During intestinal inflammation, immature cells within the intestinal crypt are called upon to replenish lost epithelial cell populations, promote tissue regeneration, and restore barrier integrity. Inflammatory mediators including T_H1/T_H17-associated cytokines influence tissue health and regenerative processes, yet how these cytokines directly influence the colon crypt epithelium and whether the crypt remains responsive to these cytokines during active damage and repair, remain unclear. Here, using laser-capture microdissection and primary colon organoid culture, we show that the cytokine milieu regulates the ability of the colonic crypt epithelium to participate in proinflammatory signaling. IFN-γ induces the T_H1-recruiting, proinflammatory chemokine CXCL10/IP10 in primary murine intestinal crypt epithelium. CXCL10 was also induced in colonic organoids derived from mice with active, experimentally induced colitis, suggesting that the crypt can actively secrete CXCL10 in select cytokine environments during colitis. Colon expression of cxcl10 further increased during infectious and noninfectious colitis in Il17a^-/- mice, demonstrating that IL-17A exerts a negative effect on CXCL10 in vivo. Furthermore, IL-17A directly antagonized CXCL10 production in ex vivo organoid cultures derived from healthy murine colons. Interestingly, direct antagonism of CXCL10 was not observed in organoids derived from colitic mouse colons bearing active lesions. These data, highlighting the complex interplay between the cytokine milieu and crypt epithelia, demonstrate proinflammatory chemokines can be induced within the colonic crypt and suggest the crypt remains responsive to cytokine modulation during inflammation.NEW & NOTEWORTHY Upon damage, the intestinal epithelium regenerates to restore barrier function. Here we observe that the local colonic cytokine milieu controls the production of procolitic chemokines within the crypt base and colon crypts remain responsive to cytokines during inflammation. IFN-γ promotes, while IL-17 antagonizes, CXCL10 production in healthy colonic crypts, while responses to cytokines differ in inflamed colon epithelium. These data reveal novel insight into colon crypt responses and inflammation-relevant alterations in signaling.

Contribution of the Microbiota to Intestinal Homeostasis and its Role in the Pathogenesis of HIV-1 Infection

During HIV infection, massive destruction of CD4+ T cells ensues, preferentially depleting the Th17 subset at the gut-associated lymphoid tissue (GALT), leading to a loss of mucosal integrity and an increase in cell permeability. This process favors microbial translocation between the intestinal lumen and the circulatory system, contributing to persistent immune activation and chronic inflammation characteristic of HIV infection. Thus, the gut microbiota plays an integral role in maintaining the structure and function of the mucosal barrier, a critical factor for immune homeostasis. However, in the context of HIV infection, changes in the gut microbiota have been reported and have been linked to disease progression. Here, we review evidence for the role of the gut microbiota in intestinal homeostasis, its contribution to HIV pathogenesis, as well as its use in the development of therapeutic strategies.

TLR5 Activation Exacerbates Airway Inflammation in Asthma

INTRODUCTION

Innate immune activation through exposure to indoor and outdoor pollutants is emerging as an important determinant of asthma severity. For example, household levels of the bacterial product lipopolysaccharide (LPS) are associated with increased asthma severity. We hypothesized that activation of the innate immune receptor TLR5 by its bacterial ligand flagellin will exacerbate airway inflammation and asthma symptoms.

METHODS

We determined the effect of flagellin co-exposure with ovalbumin in a murine model of allergic asthma. We evaluated the presence of flagellin activity in house dust of asthma patients. Finally, we analyzed the association of a dominant-negative polymorphism in TLR5 (rs5744168) with asthma symptoms in patients with asthma.

RESULTS

We showed that bacterial flagellin can be found in the house dust of patients with asthma and that this bacterial product exacerbates allergic airway inflammation in an allergen-specific mouse model of asthma. Furthermore, a dominant-negative genetic polymorphism in TLR5, the receptor for flagellin, is associated with decreased symptoms in patients with asthma.

CONCLUSION

Together, our results reveal a novel genetic protective factor (TLR5 deficiency) and a novel environmental pollutant (microbial flagellin) that influence asthma severity. (Clinical trials NCT01688986 and NCT01087307).

CD28-Dependent CTLA-4 Expression Fine-Tunes the Activation of Human Th17 Cells

Previous work has demonstrated that Th17 memory cells but not Th1 cells are resistant to CD28/CTLA-4 blockade with CTLA-4 Ig, leading us to investigate the individual roles of the CD28 and CTLA-4 cosignaling pathways on Th1 versus Th17 cells. We found that selective CD28 blockade with a domain antibody (dAb) inhibited Th1 cells but surprisingly augmented Th17 responses. CD28 agonism resulted in a profound increase in CTLA-4 expression in Th17 cells as compared with Th1 cells. Consistent with these findings, inhibition of the CD28 signaling protein AKT revealed that CTLA-4 expression on Th17 cells was more significantly reduced by AKT inhibition relative to CTLA-4 expression on Th17 cells. Finally, we found that FOXO1 and FOXO3 overexpression restrained high expression of CTLA-4 on Th17 cells but not Th1 cells. This study demonstrates that the heterogeneity of the CD4⁺ T cell compartment has implications for the immunomodulation of pathologic T cell responses.

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CD28 blockade resulted in augmentation of human Th17 cells relative to Th1 cells

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Th17 polarized mice exhibited graft rejection in the presence of CD28 blockade

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A significant portion of Th17 cell CTLA-4 expression was induced by CD28 ligation

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Overexpression of FOXO1 or FOXO3 inhibited Th17 cell CTLA-4 expression

Interleukin-17A Serves a Priming Role in Autoimmunity by Recruiting IL-1β-Producing Myeloid Cells that Promote Pathogenic T Cells

Interleukin-17A (IL-17A) is a major mediator of tissue inflammation in many autoimmune diseases. Anti-IL-17A is an effective treatment for psoriasis and is showing promise in clinical trials in multiple sclerosis. In this study, we find that IL-17A-defective mice or mice treated with anti-IL-17A at induction of experimental autoimmune encephalomyelitis (EAE) are resistant to disease and have defective priming of IL-17-secreting γδ T (γδT17) cells and Th17 cells. However, T cells from Il17a^-/- mice induce EAE in wild-type mice following in vitro culture with autoantigen, IL-1β, and IL-23. Furthermore, treatment with IL-1β or IL-17A at induction of EAE restores disease in Il17a^-/- mice. Importantly, mobilization of IL-1β-producing neutrophils and inflammatory monocytes and activation of γδT17 cells is reduced in Il17a^-/- mice. Our findings demonstrate that a key function of IL-17A in central nervous system (CNS) autoimmunity is to recruit IL-1β-secreting myeloid cells that prime pathogenic γδT17 and Th17 cells.

T cell populations in children with autism spectrum disorder and co-morbid gastrointestinal symptoms

Children with ASD are more likely to experience gastrointestinal (GI) symptoms than typically-developed children. Numerous studies have reported immune abnormalities and inflammatory profiles in the majority of individuals with ASD. Immune dysfunction is often hypothesized as a driving factor in many GI diseases and it has been suggested that it is more apparent in children with ASD that exhibit GI symptoms. In this study we sought to characterize peripheral T cell subsets in children with and without GI symptoms, compared to healthy typically-developing children. Peripheral blood mononuclear cells were isolated from participants, who were categorized into three groups: children with ASD who experience GI symptoms (n ​= ​14), children with ASD who do not experience GI symptoms (n ​= ​10) and typically-developing children who do not experience GI symptoms (n ​= ​15). In order to be included in the GI group, GI symptoms such as diarrhea, constipation, and/or pain while defecating, had to be present in the child regularly for the past 6 months; likewise, in order to be placed in the no GI groups, bowel movements could not include the above symptoms present throughout development. Cells were assessed for surface markers and intracellular cytokines to identify T cell populations. Children with ASD and GI symptoms displayed elevated TH17 populations (0.757% ​± ​0.313% compared to 0.297% ​± ​0.197), while children with ASD who did not experience GI symptoms showed increased frequency of TH2 populations (2.02% ​± ​1.08% compared to 1.01% ​± ​0.58%). Both ASD groups showed evidence of reduced gut homing regulatory T cell populations compared to typically developing children (ASDGI:1.93% ​± ​0.75% and ASDNoGI:1.85% ​± ​0.89 compared to 2.93% ​± ​1.16%). Children with ASD may have deficits in immune regulation that lead to differential inflammatory T cell subsets that could be linked to associated co-morbidities.

Expression of Th1/Th2 cell-related chemokine receptors on CD4+ lymphocytes under physiological conditions

INTRODUCTION

Chemokine receptors (CRs) and the prostaglandin D₂ receptor, CRTH2, have been used as surrogate markers for cytoplasmic Th1 and Th2 cytokines. The presence of regulatory T (Treg) and Th17 cells may affect the analysis of such surrogate markers, as they share several CRs with Th1 and Th2 cells. This study aimed to determine the optimal surrogate markers of Th1 and Th2 cells under physiological conditions.

METHODS

Surface and cytoplasmic markers of CD4⁺ peripheral lymphocytes were analyzed in healthy volunteers by flow cytometry. Th1, Th2, Th17, and Treg cells were identified as IFN-γ⁺ , IL-4⁺ IL-13⁺ , IL-17⁺ , and CD25⁺ FoxP3⁺ CD4⁺ lymphocytes, respectively.

RESULTS

The percentages of CXCR3⁺ and CCR5⁺ CD4⁺ lymphocytes clearly correlated with those of Th1 cells. The percentage of CRTH2⁺ CD4⁺ lymphocytes showed the closest correlation with that of Th2 cells. The percentages of Th2 cells correlated with those of CCR3⁺ or CCR8⁺ CD4⁺ lymphocytes, with the majority of CCR3⁺ and CCR8⁺ cells unlikely to be Th2 cells, themselves. The proportions of CCR4⁺ or CCR7⁺ CD4⁺ lymphocytes did not correlate with those of Th2 cells, possibly due to their expression on the surface of Treg and Th17 cells. Th2-related receptors were classified into three different groups for better understanding.

CONCLUSION

CXCR3 and CCR5 are useful markers of Th1 cells. With the exception of CCR4 and CCR7 expressed at measurable levels on Treg and Th17 cells, CRTH2 and CRs, CCR3, and CCR8 may be employed as surrogate markers of Th2 cells. The proposed surrogate markers may help physicians in interpreting the disease state.

Rebound of disease activity after fingolimod withdrawal: Immunological and gene expression profiling

Discontinuation of disease-modifying therapy with fingolimod can lead to severe Multiple Sclerosis (MS) rebound activity; however, this phenomenon remains mechanistically incompletely understood, and the short-term impact of a therapy switch on inflammatory gene expression in T lymphocytes is unknown. We present the clinico-radiological and immunological description of a case of rebound activity after fingolimod discontinuation and switching to rituximab treatment in a relapsing-remitting MS patient. After severe rebound, a reduction in the expression of inflammatory cytokines and transcription factors was rapidly observed after administration of methylprednisolone and rituximab. Rituximab led to an effective suppression of inflammatory activity, and at least in this specific case it represented a valid switching approach after fingolimod discontinuation.

Dissecting the Heterogeneity in T-Cell Mediated Inflammation in IBD

Infiltration of the lamina propria by inflammatory CD4⁺ T-cell populations is a key characteristic of chronic intestinal inflammation. Memory-phenotype CD4⁺ T-cell frequencies are increased in inflamed intestinal tissue of IBD patients compared to tissue of healthy controls and are associated with disease flares and a more complicated disease course. Therefore, a tightly controlled balance between regulatory and inflammatory CD4⁺ T-cell populations is crucial to prevent uncontrolled CD4⁺ T-cell responses and subsequent intestinal tissue damage. While at steady state, T-cells display mainly a regulatory phenotype, increased in Th1, Th2, Th9, Th17, and Th17.1 responses, and reduced Treg and Tr1 responses have all been suggested to play a role in IBD pathophysiology. However, it is highly unlikely that all these responses are altered in each individual patient. With the rapidly expanding plethora of therapeutic options to inhibit inflammatory T-cell responses and stimulate regulatory T-cell responses, a crucial need is emerging for a robust set of immunological assays to predict and monitor therapeutic success at an individual level. Consequently, it is crucial to differentiate dominant inflammatory and regulatory CD4⁺ T helper responses in patients and relate these to disease course and therapy response. In this review, we provide an overview of how intestinal CD4⁺ T-cell responses arise, discuss the main phenotypes of CD4⁺ T helper responses, and review how they are implicated in IBD.

Interrogating host immunity to predict treatment response in inflammatory bowel disease

IBD treatment is undergoing a transformation with an expanding repertoire of drugs targeting different aspects of the immune response. Three novel classes of drugs have emerged in the past decade that target leukocyte trafficking to the gut (vedolizumab), neutralize key cytokines with antibodies (ustekinumab) and inhibit cytokine signalling pathways (tofacitinib). In advanced development are other drugs for IBD, including therapies targeting other cytokines such as IL-23 and IL-6. However, all agents tested so far are hampered by primary and secondary loss of response, so it is desirable to develop personalized strategies to identify which patients should be treated with which drugs. Stratification of patients with IBD by clinical parameters alone lacks sensitivity, and alternative modalities are now needed to deliver precision medicine in IBD. High-resolution profiling of immune response networks in individual patients is a promising approach and different technical platforms, including in vivo real-time molecular endoscopy, tissue transcriptomics and germline genetics, are promising tools to help predict responses to specific therapies. However, important challenges remain regarding the clinical utility of these technologies, including their scalability and accessibility. This Review focuses on unravelling some of the complexity of mucosal immune responses in IBD pathogenesis and how current and emerging analytical platforms might be harnessed to effectively stratify and individualise IBD therapy.

IL-12 and Mucosal CD14+ Monocyte-Like Cells Induce IL-8 in Colonic Memory CD4+ T Cells of Patients With Ulcerative Colitis but not Crohn's Disease

BACKGROUND AND AIMS

CD14+ mononuclear phagocytes [MNPs] and T cells infiltrate colon in ulcerative colitis [UC]. Here we investigated how CD14+ MNPs and the cytokines they produce shape the colonic effector T cell profile.

METHODS

Colonic or mesenteric lymph node [mLNs] CD4+ T cells isolated from UC or Crohn's disease [CD] patients were stimulated with cytokines or autologous CD14+ MNPs. Cytokine expression was assessed by intracytoplasmic staining and multiplex ELISA. Unsupervised phenotypic multicolour analysis of colonic CD14+ MNPs was performed using the FlowSOM algorithm.

RESULTS

Among CD14+CD64+HLA-DR+SIRPα + MNPs, only the pro-inflammatory cytokine-producing CD163- subpopulation accumulated in inflamed UC colon and promoted mucosal IL-1β-dependent Th17, Th17/Th1, Th17/Th22 but not Th1 responses. Unsupervised phenotypic analysis of CD14+CD64+ MNPs segregated CD163- monocyte-like cells and CD163+ macrophages. Unexpectedly, IL-12, IL-1β and CD163-, but not CD163+, cells induced IL-8 expression in colonic CD4+ T cells, which co-expressed IFN-γ and/or IL-17 in UC and not CD. The CD163- monocyte-like cells increased the frequency of IL-8+IL-17+/-IFN-γ +/- T cells through IL-1β and IL-12. Finally, colonic IL-8+ T cells co-expressing GM-CSF, TNF-α and IL-6 were detected ex vivo and, promoted by IL-12 in the mucosa and mLNs in UC only.

CONCLUSIONS

Our findings established a link between monocyte-like CD163- MNPs, IL-12, IL-1β and the detection of colonic memory IL-8-producing CD4+ T cells, which might all contribute to the pathogenesis of UC.

Role of IL-17A in Chronic Rhinosinusitis With Nasal Polyp

Purpose

Th17-associated inflammation is increased in chronic rhinosinusitis with nasal polyp (CRSwNP), and is associated with disease severity and steroid resistance. Overexpressed interleukin (IL)-17A affects CRSwNP by tissue remodeling, eosinophilic accumulation, and neutrophilic infiltration. We aimed to identify the role of IL-17A in CRSwNP and to evaluate the effects of anti-IL-17A blocking antibody on nasal polyp (NP) formation using a murine NP model. Moreover, we sought to investigate whether the inhibition of mechanistic target of the rapamycin (mTOR) signal pathway could suppress IL-17A expression and NP formation.

Methods

Human sinonasal tissues from control subjects and patients with chronic rhinosinusitis (CRS) were analyzed using immunohistochemistry (IHC) and immunofluorescence staining. The effects of IL-17A neutralizing antibody and rapamycin were evaluated in a murine NP model. Mouse samples were analyzed using IHC, quantitative real-time polymerase chain reaction, and enzyme-linked immunosorbent assay.

Results

IL-17A⁺ inflammatory cells were significantly increased in number in NP from patients with CRSwNP compared to that in uncinate process tissues from control subjects and patients with CRS without NP or CRSwNP. CD68⁺ M1 macrophages dominantly expressed IL-17A, followed by neutrophils and T helper cells, in NP tissues. Neutralization of IL-17A effectively reduced the number of NPs, inflammatory cytokines, and IL-17A-producing cells, including M1 macrophages. Inhibition of IL-17A via the mTOR pathway using rapamycin also attenuated NP formation and inflammation in the murine NP model.

Conclusions

IL-17A possibly plays a role in the pathogenesis of CRSwNP, the major cellular source being M1 macrophage in NP tissues. Targeting IL-17A directly or indirectly may be an effective therapeutic strategy for CRSwNP.

Ultra-endurance triathlon performance and markers of whole-body and gut-specific inflammation

PURPOSE

To examine the influence of the Ultraman Florida triathlon (3 days of non-continuous racing; stage 1: 10 km swim and 144.8 km cycle; stage 2: 275.4 km cycle; stage 3: 84.4 km run) on circulating plasma concentrations of whole-body (C-reactive protein (CRP), interleukin (IL)-6 (IL-6), and IL-10 and surrogate gut-specific inflammatory markers (IL-17 and IL-23), and determine whether these variables are associated with performance.

METHODS

Eighteen triathletes (N = 18; 15 men, 3 women; age: 37 ± 8 yrs) were evaluated at baseline and post-race for circulating concentrations of CRP, IL-6, IL-10, IL-17, and IL-23. Blood samples were drawn two days prior to stage 1 (1600 h) and one day after stage 3 (1200 h).

RESULTS

Plasma CRP significantly increased from baseline (1985.8 ± 5962.3 ng/mL) to post-race (27,013.9 ± 12,888.8 ng/mL, p < 0.001, 13-fold increase). Both plasma IL-6 and IL-10 did not significantly change from baseline to post-race. Baseline and post-race concentrations of IL-17 and IL-23 were below detectable limits. Pearson's correlation between mean finish time and post-race IL-10 revealed a significant positive correlation (r = 0.54, p < 0.05).

CONCLUSIONS

Our results suggest that cytokines such as IL-6 and IL-10 involved in the inflammatory response return to near-baseline concentrations rapidly even after ultra-endurance events of extreme duration. The absence of IL-17 and IL-23 may suggest positive gut adaptations from ultra-endurance training. A significant positive correlation between post-race IL-10 concentrations and mean finish time may indicate that a relationship between anti-inflammatory responses and performance exists.

Recent developments and highlights in immune monitoring of allergen immunotherapy

Allergic diseases are the most common chronic immune-mediated disorders and can manifest with an enormous diversity in clinical severity and symptoms. Underlying mechanisms for the adverse immune response to allergens and its downregulation by treatment are still being revealed. As a result, there have been, and still are, major challenges in diagnosis, prediction of disease progression/evolution and treatment. Currently, the only corrective treatment available is allergen immunotherapy (AIT). AIT modifies the immune response through long-term repeated exposure to defined doses of allergen. However, as the treatment usually needs to be continued for several years to be effective, and can be accompanied by adverse reactions, many patients face difficulties completing their schedule. Long-term therapy also potentially incurs high costs. Therefore, there is a great need for objective markers to predict or to monitor individual patient's beneficial changes in immune response during therapy so that efficacy can be identified as early as possible. In this review, we specifically address recent technical developments that have generated new insights into allergic disease pathogenesis, and how these could potentially be translated into routine laboratory assays for disease monitoring during AIT that are relatively inexpensive, robust and scalable.

Type 3 cytokines in liver fibrosis and liver cancer

The type 3 cytokines IL-17 and IL-22 play a crucial, well synchronized physiological role in wound healing and repairing tissue damage due to infections or injury at barrier surfaces. These cytokines act on epithelial cells to induce secretion of early immune mediators, recruitment of inflammatory cells to the site of injury, and to trigger tissue repair mechanisms. However, if the damage persists or if these cytokines are dysregulated, then they contribute to a number of inflammatory pathologies, autoimmune conditions and cancer. The liver is a multifunctional organ that plays an essential role in metabolism, detoxification, and immune surveillance. It is also exposed to a variety of pathogens, toxins and injuries. Over the past decade, IL-17 and IL-22 have been implicated in various aspects of liver inflammation. IL-17 is upregulated in chronic liver injury and associated with liver disease progression. In contrast, IL-22 was shown to be hepatoprotective during acute liver injury but exhibited inflammatory effects in other models. Furthermore, IL-22 and IL-17 are both associated with poor prognosis in liver cancer. Finally, the regulatory mechanisms governing the physiological versus the pathological role of these two cytokines during acute and chronic liver injury remain poorly understood. In this review, we will summarize the current state of knowledge about IL-17 and IL-22 in wound healing during acute and chronic liver injury, their contribution to pathogenesis, their regulation, and their role in the transition from advanced liver disease to liver cancer.

A Comprehensive Review and Update on the Pathogenesis of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic and life-threating inflammatory disease of gastroenteric tissue characterized by episodes of intestinal inflammation. The pathogenesis of IBD is complex. Recent studies have greatly improved our knowledge of the pathophysiology of IBD, leading to great advances in the treatment as well as diagnosis of IBD. In this review, we have systemically reviewed the pathogenesis of IBD and highlighted recent advances in host genetic factors, gut microbiota, and environmental factors and, especially, in abnormal innate and adaptive immune responses and their interactions, which may hold the keys to identify novel predictive or prognostic biomarkers and develop new therapies.

CD4+ CCR6+ T cells, but not γδ T cells, are important for the IL-23R-dependent progression of antigen-induced inflammatory arthritis in mice

IL‐23 plays an important role in the development of arthritis and the IL‐23 receptor (IL‐23R) is expressed on different types of T cells. However, it is not fully clear which IL‐23R⁺ T cells are critical in driving T cell‐mediated synovitis. We demonstrate, using knock‐in IL‐23R‐GFP reporter (IL‐23R^GFP/+) mice, that CD4⁺CCR6⁺ T cells and γδ T cells, but not CD8⁺ T cells, express the IL‐23R(GFP). During early arthritis, IL‐23R(GFP)⁺CD4⁺CCR6⁺ T cells, but not IL‐23R(GFP)⁺ γδ T cells, were present in the inflamed joints. IL‐23R^GFP/+ mice were bred as homozygotes to obtain IL‐23R^GFP/GFP (IL‐23R deficient/IL‐23R^−/−) mice, which express GFP under the IL‐23R promotor. Arthritis progression and joint damage were significantly milder in IL‐23R^−/− mice, which revealed less IL‐17A⁺ cells in their lymphoid tissues. Surprisingly, IL‐23R^−/− mice had increased numbers of IL‐23R(GFP)⁺CD4⁺CCR6⁺ and CCR7⁺CD4⁺CCR6⁺ T cells in their spleen compared to WT, and IL‐23 suppressed CCR7 expression in vitro. However, IL‐23R(GFP)⁺CD4⁺CCR6⁺ T cells were present in the synovium of IL‐23R^−/− mice at day 4. Finally, adoptive transfer experiments revealed that CD4⁺CCR6⁺ T cells and not γδ T cells drive arthritis progression. These data suggest that IL‐23R‐dependent T cell‐mediated synovitis is dependent on CD4⁺CCR6⁺ T cells and not on γδ T cells.

Th17 and Cognitive Impairment: Possible Mechanisms of Action

T helper 17 (Th17) cells represent a distinct population of immune cells, important in the defense of the organism against extracellular infectious agents. Because of their cytokine profile and ability to recruit other immune cell types, they are highly pro-inflammatory and are involved in the induction of several autoimmune disorders. Recent studies show that Th17 cells and their signature cytokine IL-17 have also a role in a wide variety of neurological diseases. This review article will briefly summarize the evidence linking Th17 cells to brain diseases associated with cognitive impairment, including multiple sclerosis (MS), ischemic brain injury and Alzheimer’s disease (AD). We will also investigate the mechanisms by which these cells enter the brain and induce brain damage, including direct effects of IL-17 on brain cells and indirect effects mediated through disruption of the blood-brain barrier (BBB), neurovascular dysfunction and gut-brain axis. Finally, therapeutic prospects targeting Th17 cells and IL-17 will be discussed.

The Dichotomous Nature of AZ5104 (an EGFR Inhibitor) Towards RORγ and RORγT

The RORC (RAR related orphan receptor C) gene produces two isoforms by alternative promoter usage: RORγ (nuclear receptor ROR-gamma isoform 1) and RORγT (nuclear receptor ROR-gamma isoform 1). Both proteins have distinct tissue distributions and are involved in several physiological processes, including glucose/lipid metabolism and the development of Th17 lymphocytes. Previously, we developed a stably transfected reporter cell line and used it to screen a library of kinase inhibitors. We found that AZ5104 acts as an RORγ agonist at low micromolar concentrations. Molecular docking analysis showed that this compound occupies the ligand binding domain of the receptor with a significant docking score. However, analysis of the biological activity of this compound in Th17 cells revealed that it downregulates RORγT expression and Th17-related cytokine production via inhibition of SRC-ERK-STAT3 (SRC proto-oncogene - extracellular regulated MAP kinase - signal transducer and activator of transcription 3). We thus identified a compound acting as an agonist of RORγ that, due to the inhibition of downstream elements of EGFR (epidermal growth factor receptor) signaling, exerts different biological activity towards a Th17-specific isoform. Additionally, our results may be relevant in the future for the design of treatments targeting signaling pathways that inhibit Th17-related inflammation in certain autoimmune disorders.

IL-10 producing regulatory and helper T-cells in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a highly heterogeneous autoimmune disease characterised by the production of pathogenic autoantibodies against nuclear self-antigens. The anti-inflammatory and tolerogenic cytokine Interleukin-10 appears to play a paradoxical pathogenic role in SLE and is therefore currently therapeutically targeted in clinical trials. It is generally assumed that the pathogenic effect of IL-10 in SLE is due to its growth and differentiation factor activity on autoreactive B-cells, but effects on other cells might also play a role. To date, a unique cellular source of pathogenic IL-10 in SLE has not been identified. In this review, we focus on the contribution of different CD4⁺T-cell subsets to IL-10 and autoantibody production in SLE. In particular, we discuss that IL-10 produced by different subsets of adaptive regulatory T-cells, follicular helper T-cells and extra-follicular B-helper T-cells is likely to have different effects on autoreactive B-cell responses. A better understanding of the role of IL-10 in B-cell responses and lupus would allow to identify the most promising therapies for individual SLE patients in the future.

Predominantly Antibody-Deficient Patients With Non-infectious Complications Have Reduced Naive B, Treg, Th17, and Tfh17 Cells

Background: Patients with predominantly antibody deficiency (PAD) suffer from severe and recurrent infections that require lifelong immunoglobulin replacement and prophylactic antibiotic treatment. Disease incidence is estimated to be 1:25,000 worldwide, and up to 68% of patients develop non-infectious complications (NIC) including autoimmunity, which are difficult to treat, causing high morbidity, and early mortality. Currently, the etiology of NIC is unknown, and there are no diagnostic and prognostic markers to identify patients at risk.

Objectives: To identify immune cell markers that associate with NIC in PAD patients.

Methods: We developed a standardized 11-color flow cytometry panel that was utilized for in-depth analysis of B and T cells in 62 adult PAD patients and 59 age-matched controls.

Results: Nine males had mutations in Bruton's tyrosine kinase (BTK) and were defined as having X-linked agammaglobulinemia. The remaining 53 patients were not genetically defined and were clinically diagnosed with agammaglobulinemia (n = 1), common variable immunodeficiency (CVID) (n = 32), hypogammaglobulinemia (n = 13), IgG subclass deficiency (n = 1), and specific polysaccharide antibody deficiency (n = 6). Of the 53, 30 (57%) had one or more NICs, 24 patients had reduced B-cell numbers, and 17 had reduced T-cell numbers. Both PAD–NIC and PAD+NIC groups had significantly reduced Ig class-switched memory B cells and naive CD4 and CD8 T-cell numbers. Naive and IgM memory B cells, Treg, Th17, and Tfh17 cells were specifically reduced in the PAD+NIC group. CD21^lo B cells and Tfh cells were increased in frequencies, but not in absolute numbers in PAD+NIC.

Conclusion: The previously reported increased frequencies of CD21^lo B cells and Tfh cells are the indirect result of reduced naive B-cell and T-cell numbers. Hence, correct interpretation of immunophenotyping of immunodeficiencies is critically dependent on absolute cell counts. Finally, the defects in naive B- and T-cell numbers suggest a mild combined immunodeficiency in PAD patients with NIC. Together with the reductions in Th17, Treg, and Tfh17 numbers, these key differences could be utilized as biomarkers to support definitive diagnosis and to predict for disease progression.

Expansion, isolation and first characterization of bovine Th17 lymphocytes

Interleukin 17A-producing T helper cells (Th17) are CD4+ T cells that are crucial to immunity to extracellular bacteria. The roles of these cells in the bovine species are poorly defined, because the characterization of bovine Th17 cells lags behind for want of straightforward cultivation and isolation procedures. We have developed procedures to differentiate, expand, and isolate bovine Th17 cells from circulating CD4+ T cells of adult cows. Using polyclonal stimulation with antibodies to CD3 and CD28, we expanded IL-17A-positive CD4+ T cells in a serum-free cell culture medium supplemented with TGF-β1, IL-6 and IL-2. Populations of CD4+ T cells producing IL-17A or IFN-γ or both cytokines were obtained. Isolation of IL-17A-secreting CD4+ T cells was performed by labelling surface IL-17A, followed by flow cytometry cell sorting. The sorted Th17 cells were restimulated and could be expanded for several weeks. These cells were further characterized by cytokine profiling at transcriptomic and protein levels. They produced high amounts of IL-17A and IL-17F, and moderate amounts of IL-22 and IFN-γ. The techniques developed will be useful to characterize the phenotypic and functional properties of bovine Th17 cells.

Quantifying circulating Th17 cells by qPCR: potential as diagnostic biomarker for rheumatoid arthritis

OBJECTIVE

The diagnosis of RA patients remains a challenge, especially in ACPA-negative disease. Novel T-cell subsets, particularly Th17 may be useful, although data on Th17 frequency using flow cytometry in RA are conflicting. We investigated whether a novel epigenetic qPCR assay for the quantification of Th17 could differentiate patients with RA from those with symptoms evolving towards an alternative diagnosis.

METHODS

We used a qPCR assay measuring the extent of the methylation at a key position in the IL-17 and CD4 genes. Assays were performed on whole blood from 49 healthy controls (HC) and 165 early arthritis clinic patients. Flow cytometry was further used to detect the expression of CXCR4 on Th17 cells.

RESULTS

In 75 inflammatory arthritis patients who progressed to RA, the qPCR assays showed significantly fewer Th17 cells compared with 90 patients who did not (P<0.0001). Regression models demonstrated a high predictive value for RA development (75.8% correct prediction), and particularly for the ACPA-negative group (n = 125) where Th17 and swollen joint count (SJC) were the only predictors (73% correct prediction). The chemokine receptor CXCR4 had significantly higher expression on Th17 from early RA patients (n = 11) compared with HC (n = 15).

CONCLUSION

The results of the epigenetic qPCR assay showed that low levels of Th17 cells were predictive of developing RA, particularly in the ACPA-negative patients. This could have value for insights into pathogenesis and management. The results suggest the recruitment of Th17 to the inflammatory disease site, consistent with high CXCR4 expression.

Increased plasticity of non-classic Th1 cells toward the Th17 phenotype

Objectives: To analyze occurrence and plasticity of two recently described distinct subtypes of Th1 cells named classic (CD161-/CCR6-) and non-classic (CD161+/CCR6+) Th1 cells in early rheumatoid arthritis (RA) patients and healthy controls (HCs).Methods: Frequencies of in vivo-generated Th1 cell populations were assessed after cytokine secretion assay for IFNγ/IL-17 and surface staining for CD161/CCR6. Viable Th1 cells (IFNγ+IL-17-) were sorted into classic Th1 (CD161-CCR6-) and non-classic Th1 (CD161+CCR6+) cells, trans-differentiated under different Th cell-inducing conditions, and assessed for plastic changes by analyzing the Th cell-associated cytokine and transcription factor profiles.Results: Ex vivo frequencies of classic (CD161-CCR6-) and non-classic (CD161+CCR6+) Th1 cells as well as related Th1 cell subpopulations CD161+CCR6- and CD161-/CCR6+ did not differ significantly between RA and HCs. However, trans-differentiation of ex vivo non-classic (CD161+CCR6+) and CD161-/CCR6+ Th1 cells resulted in a substantial shift toward Th17 and Th1/Th17 phenotypes, particularly under Th17-inducing conditions. In contrast, classic (CD161-/CCR6-) and CD161+CCR6- Th1 cells showed higher plasticity towards IL-4-producing cells, most of them shifting to a Th1/Th2 phenotype.Conclusion: Whereas non-classic (CD161+/CCR6+) and CD161-CCR6+ Th1 cells demonstrated an increased plasticity towards IL-17- phenotypes, classic Th1 and CD161+CCR6- Th1 cells showed more plasticity towards IL-4-producing phenotypes.

Biological and clinical significance of T helper 17 cell plasticity

Mature T helper (Th) effector cells originate following antigen recognition by naive T precursors. The maturation process is accompanied by the acquisition of specific effector functions that distinguish at least three different T helper subsets: Th1, Th2 and Th17. In general, maturation of somatic cells is accompanied by terminal differentiation. However, accumulating evidence shows that effector T cells retain a certain degree of plasticity. This is especially true for Th17 cells, which have been shown to converge towards other phenotypes in response to specific microenvironmental pressure. In this review we will discuss the experimental evidence that supports the hypothesis of Th17 plasticity, with particular emphasis on the generation of Th17-derived 'non-classic' Th1 cells, and the molecular networks that control it. Moreover, we will consider why Th17 plasticity is important for host protection, but also why it can have pathogenic functions during chronic inflammation. Regarding the last point, we will discuss a possible role for biological drugs in the control of Th17 plasticity and disease course.

Trauma Induces Interleukin-17A Expression on Th17 Cells and CD4+ Regulatory T Cells as Well as Platelet Dysfunction

Background: The organism's immune response to trauma is distinctively controlled, its dysregulation leading to severe post-traumatic complications. Platelets, CD4+ regulatory T cells (CD4+ Tregs) and T helper 17 (Th17) cells have been identified to participate in the post-traumatic immune response. Unfortunately, little is known about their exact role and potential interdependency in humans. Aims of this clinical trial were to phenotype the human immune response following injury and to identify risk factors rendering the host more susceptible to trauma induced injury.

Methods: This non-interventional prospective clinical trial enrolled patients following multiple trauma, follow up was conducted for 10 days. Peripheral blood CD4+ Tregs and Th17 cells were analyzed using flow cytometry to determine Interleukin 17A (IL-17A) expression. Hemostasis and platelet function were assessed with rotational thromboelastometry (ROTEM^®). Subgroup analysis was conducted for the factors gender, age, and trauma severity.

Results and Conclusion: This is the first clinical trial to phenotype the immune response following trauma, focusing on platelets, and the adaptive immune response. We discovered a novel increased IL-17A expression on Th17 cells and on CD4+ Tregs following trauma and describe the kinetics of the immune response. The IL-17A response on CD4+ Tregs challenges the ascribed role of CD4+ Tregs to be solely counter inflammatory in this setting. Furthermore, despite a rising number of platelets, ROTEM analysis shows post-traumatic platelet dysfunction. Subgroup analysis revealed gender, age, and trauma severity as influencing factors for several of the analyzed parameters.

Shared Transcriptional Control of Innate Lymphoid Cell and Dendritic Cell Development

Innate immunity and adaptive immunity consist of highly specialized immune lineages that depend on transcription factors for both function and development. In this review, we dissect the similarities between two innate lineages, innate lymphoid cells (ILCs) and dendritic cells (DCs), and an adaptive immune lineage, T cells. ILCs, DCs, and T cells make up four functional immune modules and interact in concert to produce a specified immune response. These three immune lineages also share transcriptional networks governing the development of each lineage, and we discuss the similarities between ILCs and DCs in this review.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Altered frequencies of Th17 and Treg cells in children and adolescents with obsessive-compulsive disorder

OBJECTIVE

Obsessive-compulsive disorder (OCD) is a debilitating neuropsychiatric disorder with an etiopathophysiology that seems to include immune alterations. Previous studies have suggested that variations in the levels of circulating T cell subpopulations may be involved in psychiatric diseases. However, the role of these cells in OCD remains unexplored. Hence, the present study aimed to examine the levels of T helper 1 (Th1), Th2, Th17 and regulatory T (Treg) cells in patients with early-onset OCD and healthy controls.

METHODS

The assessment was performed in 99 children and adolescents with OCD and 46 control subjects. The percentages of circulating Th1, Th2, Th17 and Treg cells were evaluated using flow cytometry.

RESULTS

OCD patients had significantly higher levels of Th17 cells and lower percentages of Treg cells than healthy controls (p = 0.001 and p = 0.005, respectively). Furthermore, levels of Th17 cells progressively increased with the duration (p = 0.005) and severity of OCD (p = 0.008), whereas the percentages of Treg cells significantly declined with the duration of the disorder (p = 1.8 × 10^-5).

CONCLUSIONS

These results provide more evidence of the involvement of immune dysregulation, specifically an imbalance in the levels of circulating T helper and regulatory T cells, in the pathophysiology of early-onset OCD.