Requirement of interleukin 17 receptor signaling for lung CXC chemokine and granulocyte colony-stimulating factor expression, neutrophil recruitment, and host defense

Adherent-invasive Escherichia coli LF82 disrupts the tight junctions of Caco-2 monolayers

BACKGROUND AND STUDY AIMS

Adherent invasive Escherichia coli (AIEC) are enriched in IBD (inflammatory bowel disease) patients, but the role and mechanism of AIEC in the intestinal epithelial barrier is poorly defined. We evaluated the role of the AIEC strain E. coli LF82 in vitro and investigated the role of Th17 in this process.

MATERIAL AND METHODS

After coincubation with AIEC, the epithelial barrier integrity was monitored by epithelial resistance measurements. The permeability of the barrier was evaluated by TEER (trans-epithelial electrical resistance) and mucosal-to-serosal flux rate. The presence of interepithelial tight junction proteins ZO-1 and Claudin-1 were determined by immunofluorescence and western blot analysis. Cytokines in the cell culture supernatant were assayed by enzyme-linked immunosorbent assay (ELISA).

RESULTS

AIEC infection decreased TEER and increased the mucosal-to-serosal flux rate of Lucifer yellow in the intestinal barrier model in a time- and dose-dependent manner. AIEC infection decreased the expression and changed the distribution of ZO-1 and claudin-1. It also induced the secretion of cytokines such as TNF-α and IL-17.

CONCLUSION

AIEC strain E. coli LF82 increased the permeability and disrupted the tight junctions of the intestinal epithelial barrier, revealing that AIEC plays an aggravative role in the inflammatory response.

Extra-pulmonary control of respiratory defense

Pneumonia persists as a public health crisis, representing the leading cause of death due to infection. Whether respiratory tract infections progress to pneumonia and its sequelae such as acute respiratory distress syndrome and sepsis depends on numerous underlying conditions related to both the causative agent and host. Regarding the former, pneumonia burden remains staggeringly high, despite the effectiveness of pathogen-targeting strategies such as vaccines and antibiotics. This demands a greater understanding of host features that collaborate to promote immune resistance and tissue resilience in the infected lung. Such features inside the pulmonary compartment have drawn much attention, where major advances have been made related to resident and recruited immune activity. By comparison, extra-pulmonary processes guiding pneumonia susceptibility are relatively elusive, constituting the focus of this review. Here we will highlight examples of when, how, and why tissues outside of the lungs dispatch signals that modulate local immunity in the airspaces. Topics include the liver, gut, bone marrow, brain and more, all of which contribute in direct and indirect ways to pneumonia outcome. When tuned appropriately, it has become clear that these responses can serve protective roles, and this will be considered distinctly from what would otherwise be aberrant responses characteristic of pneumonia-induced organ injury and sepsis. Further advances in this area may reveal novel targetable areas for clinical intervention that are not confined to the intra-pulmonary space.

Systemic therapy for psoriasis and the risk of cutaneous infections

Systemic treatments are important for patients with moderate-to-severe psoriasis; however, they may occasionally cause adverse infectious events. Although the risk of severe infections with psoriatic treatments is well established, little is known about cutaneous infections. Therefore, we studied the frequency of cutaneous infections in patients with psoriasis who underwent biologic treatment. A total of 878 patients (237 females and 641 males) were analyzed in this follow-up survey conducted in 2020 and based on the Western Japan Psoriasis Registry. The observed skin phenotypes were psoriasis vulgaris (83.3%), pustular psoriasis (7.5%), and psoriatic arthritis (28.9%). The most frequently prescribed systemic drug was apremilast (11.3%), followed by ixekizumab (11.0%), risankizumab (10.9%), and secukinumab (10.4%). The incidence of cutaneous bacterial infections was 12 (1.37% of the total patients), with cellulitis being the most common (8/12, 67%). The incidence of viral infections was 11 (1.25%) including the most common, herpes zoster (9/11, 82%); and that of fungal infections was 45 (5.13%) including 33 (73%) and seven (16%) patients with trichophytosis and oral candidiasis, respectively. Multivariate analysis revealed that cutaneous bacterial infections were frequently observed in patients receiving tumor necrosis factor-α (odds raio [OR] 9.917, 95% confidence interval [CI] 2.069-47.572, p = 0.004) and interleukin (IL)-17 (OR 10.798, 95% CI 2.35-49.616, p = 0.002) inhibitor treatments. A history of otitis media and treatment with oral medications (OR 4.50, 95% CI 1.281-15.804, p = 0.019 and OR 3.80, 95% CI 1.141-12.679, p = 0.03 respectively) were associated with a higher ORs for cutaneous viral infections. Furthermore, age and use of IL-17 inhibitors were associated with elevated ORs for fungal infections. In conclusion, our study reveals that systemic therapies may increase the risk of cutaneous viral infections. Therefore, dermatologists should exercise caution in this regard.

Intranasal Vaccination with Recombinant TLR2-Active Outer Membrane Vesicles Containing Sequential M2e Epitopes Protects against Lethal Influenza a Challenge

Influenza is a highly contagious respiratory disease, resulting in an estimated 3 to 5 million cases of severe illness annually. While most influenza vaccines are administered parenterally via injection, one shortcoming is that they do not generate a strong immune response at the site of infection, which can become important in a pandemic. Intranasal vaccines can generate both local and systemic protective immune responses, can reduce costs, and enhance ease of administration. Previous studies showed that parenterally administered outer membrane vesicles (OMVs) that carry sequences of the M2e protein (OMV-M2e) protect against influenza A/PR8 challenge in mice and ferrets. In the current study, we measured the effectiveness of the intranasal route of the OMV-M2e vaccine against the influenza A/PR8 strain in mice. We observed high anti-M2e IgG and IgA titers post-challenge in mice vaccinated intranasally with OMV-M2e. In addition, we observed a Th1/Tc1 bias in the vaccinated mice, and an increased Th17/Tc17 response, both of which correlated with survival to A/PR8 challenge and significantly lower lung viral titers. We conclude that the intranasal-route administration of the OMV-M2e vaccine is a promising approach toward generating protection against influenza A as it leads to an increased proinflammatory immune response correlating with survival to viral challenge.

Halofuginone-guided nano-local therapy: Nano-thermosensitive hydrogels for postoperative metastatic canine mammary carcinoma with scar removal

In female dogs, the highest morbidity and mortality rates cancer are the result of mammary adenocarcinoma, which presents with metastases in the lung. Other than early surgical removal, however, no special methods are available to treat mammary adenocarcinoma. Because human breast cancer and canine mammary carcinoma share clinical characteristics and heterogeneity, the canine model is a suitable spontaneous tumor model for breast cancer in humans. In this study, the physical swelling method was used to prepare halofuginone-loaded D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) polymer micelles nano-thermosensitive hydrogels (HTPM-gel). Furthermore, HTPM-gel was investigated via characterization, morphology, properties such as swelling experiment and in vitro release with reflecting its splendid nature. Moreover, HTPM-gel was further examined its capability to anti-proliferation, anti-migration, and anti-invasion. Ultimately, HTPM-gel was investigated for its in vivo anticancer activity in the post-operative metastatic and angiogenic canine mammary carcinoma. HTPM-gel presented spherical under transmission electron microscope (TEM) and represented grid structure under scanning electron microscope (SEM), with hydrodynamic diameter (HD) of 20.25 ± 2.5 nm and zeta potential (ZP) of 15.10 ± 1.82 mV. Additionally, HTPM-gel own excellent properties comprised of pH-dependent swelling behavior, sustained release behavior. To impede the migration, invasion, and proliferation of CMT-U27 cells, we tested the efficacy of HTPM-gel. Evaluation of in vivo anti-tumor efficacy demonstrates HTPM-gel exhibit a splendid anti-metastasis and anti-angiogenic ability, with exhibiting ideal biocompatibility. Notably, HTPM-gel also inhibited the scar formation in the healing process after surgery. In summary, HTPM-gel exhibited anti-metastasis and anti-angiogenic and scar repair features. According to the results of this study, HTPM-gel has encouraging clinical potential to treat tumors with multifunctional hydrogel.

Crosstalk between CD8+ T cells and mesenchymal stromal cells in intestine homeostasis and immunity

The intestine represents the most complex cellular network in the whole body. It is constantly faced with multiple types of immunostimulatory agents encompassing from food antigen, gut microbiome, metabolic waste products, and dead cell debris. Within the intestine, most T cells are found in three primary compartments: the organized gut-associated lymphoid tissue, the lamina propria, and the epithelium. The well-orchestrated epithelial-immune-microbial interaction is critically important for the precise immune response. The main role of intestinal mesenchymal stromal cells is to support a structural framework within the gut wall. However, recent evidence from stromal cell studies indicates that they also possess significant immunomodulatory functions, such as maintaining intestinal tolerance via the expression of PDL1/2 and MHC-II molecules, and promoting the development of CD103+ dendritic cells, and IgA+ plasma cells, thereby enhancing intestinal homeostasis. In this review, we will summarize the current understanding of CD8+ T cells and stromal cells alongside the intestinal tract and discuss the reciprocal interactions between T subsets and mesenchymal stromal cell populations. We will focus on how the tissue residency, migration, and function of CD8+ T cells could be potentially regulated by mesenchymal stromal cell populations and explore the molecular mediators, such as TGF-β, IL-33, and MHC-II molecules that might influence these processes. Finally, we discuss the potential pathophysiological impact of such interaction in intestine hemostasis as well as diseases of inflammation, infection, and malignancies.

UBD participates in neutrophilic asthma by promoting the activation of IL-17 signaling

Neutrophilic asthma is a persistent and severe inflammatory lung disease characterized by neutrophil activation and the mechanisms of which are not completely elucidated. Ubiquitin D (UBD) is a ubiquitin-like modifier participating in infections, immune responses, and tumorigenesis, while whether UBD involves in neutrophilic asthma needs further study. In this study, we initially found that UBD expression was significantly elevated and interleukin 17 (IL-17) signaling was enriched in the endobronchial biopsies of severe asthma along with neutrophils increasing by bioinformatics analysis. We further confirmed that UBD was upregulated in the lung tissues of neutrophilic asthma mouse model. UBD overexpression promoted IL-17 signaling activation. Knockdown of UBD suppressed the activation of IL-17 signaling. UBD interacted with TRAF2 and reduced the total and the K48-linked ubiquitination of TRAF2. However, IL-17 A stimulation increased both the total and the K48-linked ubiquitination of TRAF2. Together, these findings indicated that UBD was upregulated and played a critical role in IL-17 signaling which contributed to a better understanding of the complex mechanisms in neutrophilic asthma.

IL-17RA-Mediated Epithelial Cell Activity Prevents Severe Inflammatory Response to Helicobacter pylori Infection

Helicobacter pylori is a Gram-negative pathogen that colonizes the stomach, induces inflammation, and drives pathological changes in the stomach tissue, including gastric cancer. As the principal cytokine produced by Th17 cells, IL-17 mediates protective immunity against pathogens by inducing the activation and mobilization of neutrophils. Whereas IL-17A is largely produced by lymphocytes, the IL-17 receptor is expressed in epithelial cells, fibroblasts, and hematopoietic cells. Loss of the IL-17RA in mice results in impaired antimicrobial responses to extracellular bacteria. In the context of H. pylori infection, this is compounded by extensive inflammation in Il17ra-/- mice. In this study, Foxa3creIl17rafl/fl (Il17raΔGI-Epi) and Il17rafl/fl (control) mice were used to test the hypothesis that IL-17RA signaling, specifically in epithelial cells, protects against severe inflammation after H. pylori infection. The data indicate that Il17raΔGI-Epi mice develop increased inflammation compared with controls. Despite reduced Pigr expression, levels of IgA increased in the gastric wash, suggesting significant increase in Ag-specific activation of the T follicular helper/B cell axis. Gene expression analysis of stomach tissues indicate that both acute and chronic responses are significantly increased in Il17raΔGI-Epi mice compared with controls. These data suggest that a deficiency of IL-17RA in epithelial cells is sufficient to drive chronic inflammation and hyperactivation of the Th17/T follicular helper/B cell axis but is not required for recruitment of polymorphonuclear neutrophils. Furthermore, the data suggest that fibroblasts can produce chemokines in response to IL-17 and may contribute to H. pylori-induced inflammation through this pathway.

Disruption of IL-17-mediated immunosurveillance in the respiratory mucosa results in invasive Streptococcus pyogenes infection

Introduction

Streptococcus pyogenes is a Gram-positive pathogen that causes a significant global burden of skin pyoderma and pharyngitis. In some cases, infection can lead to severe invasive streptococcal diseases. Previous studies have shown that IL-17 deficiency in mice (IL-17-/-) can reduce S. pyogenes clearance from the mucosal surfaces. However, the effect of IL-17 on the development of severe invasive streptococcal disease has not yet been assessed.

Methods

Here, we modeled single or repeated non-lethal intranasal (IN) S. pyogenes M1 strain infections in immunocompetent and IL-17-/- mice to assess bacterial colonization following a final IN or skin challenge.

Results

Immunocompetent mice that received a single S. pyogenes infection showed long-lasting immunity to subsequent IN infection, and no bacteria were detected in the lymph nodes or spleens. However, in the absence of IL-17, a single IN infection resulted in dissemination of S. pyogenes to the lymphoid organs, which was accentuated by repeated IN infections. In contrast to what was observed in the respiratory mucosa, skin immunity did not correlate with the systemic levels of IL-17. Instead, it was found to be associated with the activation of germinal center responses and accumulation of neutrophils in the spleen.

Discussion

Our results demonstrated that IL-17 plays a critical role in preventing invasive disease following S. pyogenes infection of the respiratory tract.

The role of ixekizumab in the treatment of nonradiographic axial spondyloarthritis

Nonradiographic axial spondyloarthritis (nr-axSpA) is a subtype of SpA with undeveloped definite radiographic sacroiliitis. Tumor necrosis factor inhibitors have demonstrated effectiveness in nr-axSpA patients who do not respond to first-line therapy. More recently, accumulated data from genetic, experimental, and clinical studies revealed that IL-17 is a key player in the pathogenesis of SpA, leading to development of new biologics directly inhibiting IL-17. Among them, ixekizumab is a high-affinity monoclonal antibody that selectively targets IL-17A and has exhibited significant efficacy and acceptable safety profiles in the treatment of nr-axSpA. The aim of this paper is to narratively review the recent insights of IL-17 in the pathogenesis of axSpA and discuss the effectiveness and safety of ixekizumab in treatment of nr-axSpA.

Characteristics of Immunocytes and Cytokines in Patients with Bloodstream Infections Caused by Carbapenem-Resistant Klebsiella pneumoniae in China

Objective

To evaluate the characteristics of immunocytes and cytokines associated with bloodstream infections (BSIs) caused by carbapenem-resistant Klebsiella pneumoniae (CRKP).

Methods

Patients with BSIs K. pneumoniae (BSIs-Kpn) were enrolled in our hospital between 2015 and 2022. Whole blood and serum samples were collected on the first day after diagnosis. Immunocytes and cytokines profiles were assessed using multicolor flow cytometry and multiplex immunoassays, respectively. The test cytokines included interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-2, IL-4, IL-6, IL-10, and IL-17A.

Results

A total of 313 patients had BSIs-Kpn, including 145 with CRKP, 43 with extended-spectrum β-lactamases (ESBL) producing Kpn (ESBL-Kpn) and 125 with non-CRKP or non-ESBL-Kpn (susceptible Kpn, S-Kpn). Absolute number of leukomonocyte (CD45+) in CRKP, ESBL-Kpn and S-Kpn were 280.0 (138.0-523.0) cells/μL, 354.5 (150.3-737.3) cells/μL, and 637.0 (245.0-996.5) cells/μL, respectively. Compared with S-Kpn group, the absolute numbers of leukomonocyte (including T lymphocytes, B lymphocytes and natural killer cells) in patients with CRKP were significantly lower than that in patients with S-Kpn (P < 0.01). The levels of cytokines IL-2 and IL-17A were significantly higher in patients with S-Kpn than in those patients with CRKP (P<0.05). The area under receiver operating curve (AUC) of IL-2, IL-4, and IL-17A for S-Kpn was 0.576, 0.513, and 0.561, respectively, whereas that for the combination of these three cytokines with immunocytes was 0.804.

Conclusion

Patients with BSIs-CRKP had lower leukomonocyte counts. High levels of IL-2 and IL-17A combined with immunocyte subpopulations showed relatively high diagnostic value for BSIs-S-Kpn from BSIs-CRKP.

IL-17 and IL-21: Their Immunobiology and Therapeutic Potentials

Studies over the last 2 decades have identified IL-17 and IL-21 as key cytokines in the modulation of a wide range of immune responses. IL-17 serves as a critical defender against bacterial and fungal pathogens, while maintaining symbiotic relationships with commensal microbiota. However, alterations in its levels can lead to chronic inflammation and autoimmunity. IL-21, on the other hand, bridges the adaptive and innate immune responses, and its imbalance is implicated in autoimmune diseases and cancer, highlighting its important role in both health and disease. Delving into the intricacies of these cytokines not only opens new avenues for understanding the immune system, but also promises innovative advances in the development of therapeutic strategies for numerous diseases. In this review, we will discuss an updated view of the immunobiology and therapeutic potential of IL-17 and IL-21.

The IL-17 pathway as a target in giant cell arteritis

The network of IL-17 cytokines is considered a key component of autoimmune and inflammatory processes. Blocking IL-17 showed great success in psoriasis as well as psoriatic arthritis, and in patients with axial spondyloarthritis. Secukinumab is one of the approved IL-17A inhibitors for these diseases and is now routinely used. In giant cell arteritis, a large vessel vasculitis, there is accumulating evidence for a pathogenic role of IL-17 and Th17 cells, which are part of the CD4+ T-cell subset. Giant cell arteritis occurs in individuals over 50 years of age and many have relative contraindications to glucocorticoid therapy, which today still represents the mainstay therapy. Despite the approval of tocilizumab, which targets the IL-6 receptor, a high demand for glucocorticoid-sparing agents remains that combine the effective suppression of the acute inflammation observed in giant cell arteritis with a safety profile that matches the needs of an older patient population. The first results from a phase II proof-of-principle study (TitAIN) support an optimistic outlook on a potential new treatment option with secukinumab in giant cell arteritis.

Social anxiety disorder-associated gut microbiota increases social fear

Social anxiety disorder (SAD) is a crippling psychiatric disorder characterized by intense fear or anxiety in social situations and their avoidance. However, the underlying biology of SAD is unclear and better treatments are needed. Recently, the gut microbiota has emerged as a key regulator of both brain and behaviour, especially those related to social function. Moreover, increasing data supports a role for immune function and oxytocin signalling in social responses. To investigate whether the gut microbiota plays a causal role in modulating behaviours relevant to SAD, we transplanted the microbiota from SAD patients, which was identified by 16S rRNA sequencing to be of a differential composition compared to healthy controls, to mice. Although the mice that received the SAD microbiota had normal behaviours across a battery of tests designed to assess depression and general anxiety-like behaviours, they had a specific heightened sensitivity to social fear, a model of SAD. This distinct heightened social fear response was coupled with changes in central and peripheral immune function and oxytocin expression in the bed nucleus of the stria terminalis. This work demonstrates an interkingdom basis for social fear responses and posits the microbiome as a potential therapeutic target for SAD.

STAT1 Employs Myeloid Cell-Extrinsic Mechanisms to Regulate the Neutrophil Response and Provide Protection against Invasive Klebsiella pneumoniae Lung Infection

Klebsiella pneumoniae (KP) is an extracellular Gram-negative bacterium that causes infections in the lower respiratory and urinary tracts and the bloodstream. STAT1 is a master transcription factor that acts to maintain T cell quiescence under homeostatic conditions. Although STAT1 helps defend against systemic spread of acute KP intrapulmonary infection, whether STAT1 regulation of T cell homeostasis impacts pulmonary host defense during acute bacterial infection and injury is less clear. Using a clinical KP respiratory isolate and a pneumonia mouse model, we found that STAT1 deficiency led to an early neutrophil-dominant transcriptional profile and neutrophil recruitment in the lung preceding widespread bacterial dissemination and lung injury development. Yet, myeloid cell STAT1 was dispensable for control of KP proliferation and dissemination, because myeloid cell-specific STAT1-deficient (LysMCre/WT;Stat1fl/fl) mice showed bacterial burden in the lung, liver, and kidney similar to that of their wild-type littermates. Surprisingly, IL-17-producing CD4+ T cells infiltrated Stat1-/- murine lungs early during KP infection. The increase in Th17 cells in the lung was not due to preexisting immunity against KP and was consistent with circulating rather than tissue-resident CD4+ T cells. However, blocking global IL-17 signaling with anti-IL-17RC administration led to increased proliferation and dissemination of KP, suggesting that IL-17 provided by other innate immune cells is essential in defense against KP. Contrastingly, depletion of CD4+ T cells reduced Stat1-/- murine lung bacterial burden, indicating that early CD4+ T cell activation in the setting of global STAT1 deficiency is pathogenic. Altogether, our findings suggest that STAT1 employs myeloid cell-extrinsic mechanisms to regulate neutrophil responses and provides protection against invasive KP by restricting nonspecific CD4+ T cell activation and immunopathology in the lung.

Clinicopathological studies on ulcerative lymphangitis in cattle: Alterations in serum inflammatory cytokines, anti-microbial, organs functions, and oxidative stress-related biomarkers

Background

Affection with Corynebacterium pseudotuberculosis (C. pseudotuberculosis) and development of cellulitis and/or abscess formation with cutaneous lymphangitis in cattle is rare to some extent, so literature about the biochemical changes that would accompany this infection is rare.

Aim

In this context, the present study was designed to screen the effect of the infection with C. pseudotuberculosis cutaneous lymphangitis on the release of some immune molecules, organ functions, and redox state in Baladi cows.

Methods

Fourteen Baladi cows from a small dairy farm in El-Behira, Egypt, were selected to complete this study. After bacteriological culture confirmation, seven of them were found suffering from cutaneous lesions due to infection with C. pseudotuberculosis (Diseased group), while the others were healthy (Healthy group). Serum samples were obtained to evaluate the presumptive changes in some clinicopathological parameters.

Results

Serum analysis revealed a significant decrease in the levels of interferon-gamma and interleukin-17 as well as a significant decrement in the concentration of beta-defensin (β-defensin) and lipocalin-2. While serum level of interleukin-10 recorded a significant increase in these animals when compared to healthy control animals. Concurrently, the affected animals recorded a significant elevation in serum levels of hepato-cardiac enzymes, urea, and creatinine in addition to disturbance in the serum redox state.

Conclusion

In conclusion, infection with C. pseudotuberculosis cattle may disturb the defensive immune state, body organ function, and redox state of the animals.

Physiological roles of human interleukin-17 family

Interleukin-17 s (IL-17s) are well-known proinflammatory cytokines, and their antagonists perform excellently in the treatment of inflammatory skin diseases such as psoriasis. However, their physiological functions have not been given sufficient attention by clinicians. IL-17s can protect the host from extracellular pathogens, maintain epithelial integrity, regulate cognitive processes and modulate adipocyte activity through distinct mechanisms. Here, we present a systematic review concerning the physiological functions of IL-17s. Our goal is not to negate the therapeutic effect of IL-17 antagonists, but to ensure their safe use and reasonably explain the possible adverse events that may occur in their application.

BATF2 enhances proinflammatory cytokine responses in macrophages and improves early host defense against pulmonary Klebsiella pneumoniae infection

Basic leucine zipper transcription factor ATF-like 2 (BATF2) is a transcription factor that is emerging as an important regulator of the innate immune system. BATF2 is among the top upregulated genes in human alveolar macrophages treated with LPS, but the signaling pathways that induce BATF2 expression in response to Gram-negative stimuli are incompletely understood. In addition, the role of BATF2 in the host response to pulmonary infection with a Gram-negative pathogen like Klebsiella pneumoniae (Kp) is not known. We show that induction of Batf2 gene expression in macrophages in response to Kp in vitro requires TRIF and type I interferon (IFN) signaling, but not MyD88 signaling. Analysis of the impact of BATF2 deficiency on macrophage effector functions in vitro showed that BATF2 does not directly impact macrophage phagocytic uptake and intracellular killing of Kp. However, BATF2 markedly enhanced macrophage proinflammatory gene expression and Kp-induced cytokine responses. In vivo, Batf2 gene expression was elevated in lung tissue of wild-type (WT) mice 24 h after pulmonary Kp infection, and Kp-infected BATF2-deficient (Batf2-/-) mice displayed an increase in bacterial burden in the lung, spleen, and liver compared with WT mice. WT and Batf2-/- mice showed similar recruitment of leukocytes following infection, but in line with in vitro observations, proinflammatory cytokine levels in the alveolar space were reduced in Batf2-/- mice. Altogether, these results suggest that BATF2 enhances proinflammatory cytokine responses in macrophages in response to Kp and contributes to the early host defense against pulmonary Kp infection.NEW & NOTEWORTHY This study investigates the signaling pathways that mediate induction of BATF2 expression downstream of TLR4 and also the impact of BATF2 on the host defense against pulmonary Kp infection. We demonstrate that Kp-induced upregulation of BATF2 in macrophages requires TRIF and type I IFN signaling. We also show that BATF2 enhances Kp-induced macrophage cytokine responses and that BATF2 contributes to the early host defense against pulmonary Kp infection.

The IL-17 family in diseases: from bench to bedside

The interleukin-17 (IL-17) family comprises six members (IL-17A-17F), and recently, all of its related receptors have been discovered. IL-17 was first discovered approximately 30 years ago. Members of this family have various biological functions, including driving an inflammatory cascade during infections and autoimmune diseases, as well as boosting protective immunity against various pathogens. IL-17 is a highly versatile proinflammatory cytokine necessary for vital processes including host immune defenses, tissue repair, inflammatory disease pathogenesis, and cancer progression. However, how IL-17 performs these functions remains controversial. The multifunctional properties of IL-17 have attracted research interest, and emerging data have gradually improved our understanding of the IL-17 signaling pathway. However, a comprehensive review is required to understand its role in both host defense functions and pathogenesis in the body. This review can aid researchers in better understanding the mechanisms underlying IL-17's roles in vivo and provide a theoretical basis for future studies aiming to regulate IL-17 expression and function. This review discusses recent progress in understanding the IL-17 signaling pathway and its physiological roles. In addition, we present the mechanism underlying IL-17's role in various pathologies, particularly, in IL-17-induced systemic lupus erythematosus and IL-17-related tumor cell transformation and metastasis. In addition, we have briefly discussed promising developments in the diagnosis and treatment of autoimmune diseases and tumors.

The role of CD4+ T cells in tumor and chronic viral immune responses

Immunotherapies are mainly aimed to promote a CD8+ T cell response rather than a CD4+ T cell response as cytotoxic T lymphocytes (CTLs) can directly kill target cells. Recently, CD4+ T cells have received more attention due to their diverse roles in tumors and chronic viral infections. In antitumor and antichronic viral responses, CD4+ T cells relay help signals through dendritic cells to indirectly regulate CD8+ T cell response, interact with B cells or macrophages to indirectly modulate humoral immunity or macrophage polarization, and inhibit tumor blood vessel formation. Additionally, CD4+ T cells can also exhibit direct cytotoxicity toward target cells. However, regulatory T cells exhibit immunosuppression and CD4+ T cells become exhausted, which promote tumor progression and chronic viral persistence. Finally, we also outline immunotherapies based on CD4+ T cells, including adoptive cell transfer, vaccines, and immune checkpoint blockade. Overall, this review summarizes diverse roles of CD4+ T cells in the antitumor or protumor and chronic viral responses, and also highlights the immunotherapies based on CD4+ T cells, giving a better understanding of their roles in tumors and chronic viral infections.

IL-17A functions and the therapeutic use of IL-17A and IL-17RA targeted antibodies for cancer treatment

Interleukin 17A (IL-17A) is a major member of the IL-17 cytokine family and is produced mainly by T helper 17 (Th17) cells. Other cells such as CD8+ T cells, γδ T cells, natural killer T cells and innate lymphoid-like cells can also produce IL-17A. In healthy individuals, IL-17A has a host-protective capacity, but excessive elevation of IL-17A is associated with the development of autoimmune diseases and cancer. Monoclonal antibodies (mAbs) targeting IL-17A (e.g., ixekizumab and secukinumab) or IL-17A receptor (IL-17RA) (e.g., brodalumab) would be investigated as potential treatments for these diseases. Currently, the application of IL-17A-targeted drugs in autoimmune diseases will provide new ideas for the treatment of tumors, and its combined application with immune checkpoint inhibitors has become a research hotspot. This article reviews the mechanism of action of IL-17A and the application of anti-IL-17A antibodies, focusing on the research progress on the mechanism of action and therapeutic blockade of IL-17A in various tumors such as colorectal cancer (CRC), lung cancer, gastric cancer and breast cancer. Moreover, we also include the results of therapeutic blockade in the field of cancer as well as recent advances in the regulation of IL-17A signaling.

Peripheral spondyloarthritis: What have we learned?

The peripheral spondyloarthritis (pSpA) entity remains poorly defined in comparison with axial SpA and psoriatic arthritis, as the clinical symptoms have low specificity, the biological markers are virtually lacking, and dedicated randomized controlled trials in this specific indication remain scarce. In addition, clinical similarities between pSpA and psoriatic arthritis (PsA) have been described, partly explained by a resemblance in the pathophysiology of both entities. Thus, diagnosing pSpA can be challenging because of the overlap with other entities and the absence of a specific test or imaging study that can definitively diagnose the condition. The aim of this review is to summarize the current understanding of pSpA, its epidemiology, physiopathology, clinical diagnosis, and classification criteria. In addition, we present patient-reported outcomes used in pSpA clinical studies, available evidence on therapies, and future directions.

Intricacies of TGF-β signaling in Treg and Th17 cell biology

Balanced immunity is pivotal for health and homeostasis. CD4+ helper T (Th) cells are central to the balance between immune tolerance and immune rejection. Th cells adopt distinct functions to maintain tolerance and clear pathogens. Dysregulation of Th cell function often leads to maladies, including autoimmunity, inflammatory disease, cancer, and infection. Regulatory T (Treg) and Th17 cells are critical Th cell types involved in immune tolerance, homeostasis, pathogenicity, and pathogen clearance. It is therefore critical to understand how Treg and Th17 cells are regulated in health and disease. Cytokines are instrumental in directing Treg and Th17 cell function. The evolutionarily conserved TGF-β (transforming growth factor-β) cytokine superfamily is of particular interest because it is central to the biology of both Treg cells that are predominantly immunosuppressive and Th17 cells that can be proinflammatory, pathogenic, and immune regulatory. How TGF-β superfamily members and their intricate signaling pathways regulate Treg and Th17 cell function is a question that has been intensely investigated for two decades. Here, we introduce the fundamental biology of TGF-β superfamily signaling, Treg cells, and Th17 cells and discuss in detail how the TGF-β superfamily contributes to Treg and Th17 cell biology through complex yet ordered and cooperative signaling networks.

Ets1 and IL17RA cooperate to regulate autoimmune responses and skin immunity to Staphylococcus aureus

Introduction

Ets1 is a lymphoid-enriched transcription factor that regulates B- and Tcell functions in development and disease. Mice that lack Ets1 (Ets1 KO) develop spontaneous autoimmune disease with high levels of autoantibodies. Naïve CD4 + T cells isolated from Ets1 KO mice differentiate more readily to Th17 cells that secrete IL-17, a cytokine implicated in autoimmune disease pathogenesis. To determine if increased IL-17 production contributes to the development of autoimmunity in Ets1 KO mice, we crossed Ets1 KO mice to mice lacking the IL-17 receptor A subunit (IL17RA KO) to generate double knockout (DKO) mice.

Methods

In this study, the status of the immune system of DKO and control mice was assessed utilizing ELISA, ELISpot, immunofluorescent microscopy, and flow cytometric analysis of the spleen, lymph node, skin. The transcriptome of ventral neck skin was analyzed through RNA sequencing. S. aureus clearance kinetics in in exogenously infected mice was conducted using bioluminescent S. aureus and tracked using an IVIS imaging experimental scheme.

Results

We found that the absence of IL17RA signaling did not prevent or ameliorate the autoimmune phenotype of Ets1 KO mice but rather that DKO animals exhibited worse symptoms with striking increases in activated B cells and secreted autoantibodies. This was correlated with a prominent increase in the numbers of T follicular helper (Tfh) cells. In addition to the autoimmune phenotype, DKO mice also showed signs of immunodeficiency and developed spontaneous skin lesions colonized by Staphylococcus xylosus. When DKO mice were experimentally infected with Staphylococcus aureus, they were unable to clear the bacteria, suggesting a general immunodeficiency to staphylococcal species. γδ T cells are important for the control of skin staphylococcal infections. We found that mice lacking Ets1 have a complete deficiency of the γδ T-cell subset dendritic epidermal T cells (DETCs), which are involved in skin woundhealing responses, but normal numbers of other skin γδ T cells. To determine if loss of DETC combined with impaired IL-17 signaling might promote susceptibility to staph infection, we depleted DETC from IL17RA KO mice and found that the combined loss of DETC and impaired IL-17 signaling leads to an impaired clearance of the infection.

Conclusions

Our studies suggest that loss of IL-17 signaling can result in enhanced autoimmunity in Ets1 deficient autoimmune-prone mice. In addition, defects in wound healing, such as that caused by loss of DETC, can cooperate with impaired IL-17 responses to lead to increased susceptibility to skin staph infections.

IL-17: Balancing Protective Immunity and Pathogenesis

The biological role of interleukin 17 (IL-17) has been explored during recent decades and identified as a pivotal player in coordinating innate and adaptive immune responses. Notably, IL-17 functions as a double-edged sword with both destructive and protective immunological roles. While substantial progress has implicated unrestrained IL-17 in a variety of infectious diseases or autoimmune conditions, IL-17 plays an important role in protecting the host against pathogens and maintaining physiological homeostasis. In this review, we describe canonical IL-17 signaling mechanisms promoting neutrophils recruitment, antimicrobial peptide production, and maintaining the epithelium barrier integrity, as well as some noncanonical mechanisms involving IL-17 that elicit protective immunity.

Integrated transcriptomic and metabolomic profiles reveal the protective mechanism of modified Danggui Buxue decoction on radiation-induced leukopenia in mice

Leukopenia caused by radiation hinders the continuous treatment of cancers. Danggui Buxue Decoction (DBD) has been widely used in clinical owing to low toxicity and definite therapeutic effects to increase leukocytes. Meanwhile, icaritin (ICT) has also been proved to have the effect of boosting peripheral blood cells proliferation. However, there is no study to prove the efficacy of MDBD (Modified Danggui Buxue Decoction), a derivative herbal formula composed of DBD and ICT, in the treatment of radiation-induced leukopenia. In this study, we performed a model of 3.5 Gy whole-body radiation to induce leukopenia in mice. The results of pharmacodynamic studies demonstrated that MDBD could significantly increase the white blood cells in peripheral blood by improving the activity of bone marrow nuclear cells, reducing bone marrow damage, modulating spleen index, and regulating hematopoietic factors to alleviate leukopenia. We also analyzed the integrated results of metabolomics and transcriptomics and found that MDBD could relieve leukopenia and alleviate bone marrow damage by targeting steroid biosynthesis and IL-17 signaling pathway, in which the key genes are Jun, Cxcl2 and Egr1. Therefore, our study provides a basis for the effectiveness and compatibility in the combination of traditional Chinese medicine formula and small molecule drugs.

Friend or Foe - Tc17 cell generation and current evidence for their importance in human disease

The term Tc17 cells refers to interleukin 17 (IL-17)-producing CD8+ T cells. While IL-17 is an important mediator of mucosal defense, it is also centrally involved in driving the inflammatory response in immune-mediated diseases, such as psoriasis, multiple sclerosis, and inflammatory bowel disease. In this review, we aim to gather the current knowledge on the phenotypic and transcriptional profile, the in vitro and in vivo generation of Tc17 cells, and the evidence pointing towards a relevant role of Tc17 cells in human diseases such as infectious diseases, cancer, and immune-mediated diseases.

Interleukin-17 as a key player in neuroimmunometabolism

In mammals, interleukin (IL)-17 cytokines are produced by innate and adaptive lymphocytes. However, the IL-17 family has widespread expression throughout evolution, dating as far back as cnidaria, molluscs and worms, which predate lymphocytes. The evolutionary conservation of IL-17 suggests that it is involved in innate defence strategies, but also that this cytokine family has a fundamental role beyond typical host defence. Throughout evolution, IL-17 seems to have a major function in homeostatic maintenance at barrier sites. Most recently, a pivotal role has been identified for IL-17 in regulating cellular metabolism, neuroimmunology and tissue physiology, particularly in adipose tissue. Here we review the emerging role of IL-17 signalling in regulating metabolic processes, which may shine a light on the evolutionary role of IL-17 beyond typical immune responses. We propose that IL-17 helps to coordinate the cross-talk among the nervous, endocrine and immune systems for whole-body energy homeostasis as a key player in neuroimmunometabolism.

IL-17 Signaling in Keratinocytes Orchestrates the Defense against Staphylococcus aureus Skin Infection

Keratinocytes (KCs) form the outer epithelial barrier of the body, protecting against invading pathogens. Mice lacking the IL-17RA or both IL-17A and IL-17F develop spontaneous Staphylococcusaureus skin infections. We found a marked expansion of T17 cells, comprised of RORγt-expressing γδ T cells and T helper 17 cells in the skin-draining lymph nodes of these mice. Contradictory to previous suggestions, this expansion was not a result of a direct negative feedback loop because we found no expansion of T17 cells in mice lacking IL-17 signaling specifically in T cells. Instead, we found that the T17 expansion depended on the microbiota and was observed only when KCs were deficient for IL-17RA signaling. Indeed, mice that lack IL-17RA only in KCs showed an increased susceptibility to experimental epicutaneous infection with S. aureus together with an accumulation of IL-17A-producing γδ T cells. We conclude that deficiency of IL-17RA on KCs leads to microbiota dysbiosis in the skin, which triggers the expansion of IL-17A-producing T cells. Our data show that KCs are the primary target cells of IL-17A and IL-17F, coordinating the defense against microbial invaders in the skin.

The Role of IL-17 in the Pathogenesis of Oral Squamous Cell Carcinoma

Elucidating the inflammatory mechanisms underlying formation and progression of oral squamous cell carcinoma (OSCC) is crucial for discovering new targeted therapeutics. The proinflammatory cytokine IL-17 has proven roles in tumor formation, growth, and metastasis. The presence of IL-17 is demonstrated in both in vitro and in vivo models, and in OSCC patients, is mostly accompanied by enhanced proliferation and invasiveness of cancer cells. Here we review the known facts regarding the role of IL-17 in OSCC pathogenesis, namely the IL-17 mediated production of proinflammatory mediators that mobilize and activate myeloid cells with suppressive and proangiogenic activities and proliferative signals that directly induce proliferation of cancer cells and stem cells. The possibility of a potential IL-17 blockade in OSCC therapy is also discussed.

Recent progress and prospects for anti-cytokine therapy in preclinical and clinical acute lung injury

Acute respiratory distress syndrome (ARDS) is a heterogeneous cause of respiratory failure that has a rapid onset, a high mortality rate, and for which there is no effective pharmacological treatment. Current evidence supports a critical role of excessive inflammation in ARDS, resulting in several cytokines, cytokine receptors, and proteins within their downstream signalling pathways being putative therapeutic targets. However, unsuccessful trials of anti-inflammatory drugs have thus far hindered progress in the field. In recent years, the prospects of precision medicine and therapeutic targeting of cytokines coevolving into effective treatments have gained notoriety. There is an optimistic and growing understanding of ARDS subphenotypes as well as advances in treatment strategies and clinical trial design. Furthermore, large trials of anti-cytokine drugs in patients with COVID-19 have provided an unprecedented amount of information that could pave the way for therapeutic breakthroughs. While current clinical and nonclinical ARDS research suggest relatively limited potential in monotherapy with anti-cytokine drugs, combination therapy has emerged as an appealing strategy and may provide new perspectives on finding safe and effective treatments. Accurate evaluation of these drugs, however, also relies on well-founded experimental research and the implementation of biomarker-guided stratification in future trials. In this review, we provide an overview of anti-cytokine therapy for acute lung injury and ARDS, highlighting the current preclinical and clinical evidence for targeting the main cytokines individually and the therapeutic prospects for combination therapy.

The role of regulatory T cells and follicular T helper cells in HBV infection

Hepatitis B has become one of the major global health threats, especially in developing countries and regions. Hepatitis B virus infection greatly increases the risk for liver diseases such as cirrhosis and cancer. However, treatment for hepatitis B is limited when considering the huge base of infected people. The immune response against hepatitis B is mediated mainly by CD8+ T cells, which are key to fighting invading viruses, while regulatory T cells prevent overreaction of the immune response process. Additionally, follicular T helper cells play a key role in B-cell activation, proliferation, differentiation, and formation of germinal centers. The pathogenic process of hepatitis B virus is generally the result of a disorder or dysfunction of the immune system. Therefore, we present in this review the critical functions and related biological processes of regulatory T cells and follicular T helper cells during HBV infection.

Genetic and Molecular Distinctions Between Axial Psoriatic Arthritis and Radiographic Axial Spondyloarthritis: Post Hoc Analyses from Four Phase 3 Clinical Trials

INTRODUCTION

Emerging evidence suggests psoriatic arthritis (PsA) with axial involvement (axPsA) and radiographic axial spondyloarthritis (r-axSpA) may possibly represent distinct disorders, with some differing clinical manifestations, genetic associations, and radiographic findings. Moreover, axPsA and r-axSpA may respond differently to therapies: guselkumab (interleukin [IL]-23p19 subunit inhibitor [i]) and ustekinumab (IL-12/23p40i) demonstrated improvements in axial symptoms in patients with PsA; however, neither risankizumab (IL-23p19i) nor ustekinumab demonstrated efficacy versus placebo in patients with r-axSpA. Current analyses aim to further understand potential molecular distinctions between axPsA and r-axSpA and examine the pharmacodynamic effects of guselkumab in patients with axPsA and those with PsA without axial involvement (non-axPsA).

METHODS

Post hoc analyses utilized biomarker data from blood and serum samples collected from a subset of participants in phase 3 studies of ustekinumab in r-axSpA and guselkumab in PsA (DISCOVER-1 and DISCOVER-2). Participants with axPsA were identified by investigator-verified sacroiliitis (imaging-confirmed) and axial symptoms. HLA mapping, serum cytokine analysis, and whole-blood RNA sequencing were conducted.

RESULTS

Relative to r-axSpA, patients with axPsA had a lower prevalence of HLA-B27, HLA-C01, and HLA-C02 alleles and a higher prevalence of HLA-B13, HLA-B38, HLA-B57, HLA-C06, and HLA-C12 alleles. Compared with r-axSpA, patients with axPsA had elevated baseline levels of serum IL-17A and IL-17F cytokines, enrichment of IL-17 and IL-10 pathway-associated genes, and neutrophil gene markers. Across axPsA and non-axPsA cohorts, reductions in cytokine levels and normalization of pathway-associated gene expression with guselkumab treatment were comparable.

CONCLUSION

The differences in HLA genetic associations, serum cytokines, and enrichment scores support the concept that axPsA and r-axSpA may be distinct disorders. The comparable pharmacodynamic effects of guselkumab on cytokine levels and pathway-associated genes observed in patients with axPsA and non-axPsA are consistent with demonstrated clinical improvements across PsA cohorts. These findings contribute to the understanding of potential genetic and molecular distinctions between axPsA and r-axSpA.

TRIAL REGISTRATION

ClinicalTrials.gov identifiers, NCT03162796, NCT0315828, NCT02437162, and NCT02438787.

IL-17 cytokines preferentially act on naïve CD4+ T cells with the IL-17AF heterodimer inducing the greatest functional changes

CD4+ T-helper 17 (Th17) T cells are a key population in protective immunity during infection and in self-tolerance/autoimmunity. Through the secretion of IL-17, Th17 cells act in promotion of inflammation and are thus a major potential therapeutic target in autoimmune disorders. Recent reports have brought to light that the IL-17 family cytokines, IL-17A, IL-17F and IL-17AF, can directly act on CD4+ T-cells, both in murine and human systems, inducing functional changes in these cells. Here we show that this action is preferentially targeted toward naïve, but not memory, CD4+ T-cells. Naïve cells showed transcriptome changes as early as 48 hours post-IL-17 exposure, whereas memory cells remained unaffected as late as 7 days. These functional differences occurred despite similar IL-17 receptor expression on these subsets and were maintained in co-culture/transwell systems, with each subset maintaining its functional response to IL-17. Importantly, there were differences in downstream transcriptional signaling by the three IL-17 cytokines, with the IL-17AF heterodimer conferring both the greatest transcriptional change and most altered functional consequences. Detailed transcriptome analysis provides important insights into the genes and pathways that are modulated as a result of IL-17-mediated signaling and may serve as targets of future therapies.

Effect and mechanism of terahertz irradiation in repairing spinal cord injury in mice

SIGNIFICANCE

Spinal cord injury (SCI) represents a serious trauma to the central nervous system. Terahertz (THz) irradiation is an emerging technique, it has potential application prospects in the treatment of central nervous system diseases.

AIM

We report on the investigation of the effect and mechanism of THz irradiation in repairing SCI in mice.

APPROACH

The effect of THz in SCI was evaluated by the expression of inflammatory factors, the mouse behavioral scale (BMS), and immunofluorescence staining. After RNA sequencing (RNA-seq), we determined the differentially expressed genes (DEGs) and performed GO and KEGG analysis.

RESULTS

After THz irradiation, the inflammatory response, the behavioral function, and the severity of SCI recovered well, indicating that THz irradiation can effectively promote the repair of SCI. GO and KEGG results show that genes related to inflammation, immune regulation, and IL-17 signaling pathway may play an important role in this process.

CONCLUSIONS

THz irradiation can effectively promote the repair of SCI. Genes related to inflammation, immune regulation, and IL-17 signaling pathway may play an important role in this process.

The Airway Microbiome-IL-17 Axis: a Critical Regulator of Chronic Inflammatory Disease

The respiratory tract is home to a diverse microbial community whose influence on local and systemic immune responses is only beginning to be appreciated. Increasing reports have linked changes in this microbiome to a range of pulmonary and extrapulmonary disorders, including asthma, chronic obstructive pulmonary disease and rheumatoid arthritis. Central to many of these findings is the role of IL-17-type immunity as an important driver of inflammation. Despite the crucial role played by IL-17-mediated immune responses in protection against infection, overt Th17 cell responses have been implicated in the pathogenesis of several chronic inflammatory diseases. However, our knowledge of the influence of bacteria that commonly colonise the respiratory tract on IL-17-driven inflammatory responses remains sparse. In this article, we review the current knowledge on the role of specific members of the airway microbiota in the modulation of IL-17-type immunity and discuss how this line of research may support the testing of susceptible individuals and targeting of inflammation at its earliest stages in the hope of preventing the development of chronic disease.

Targeted Therapies in Psoriatic Arthritis—An Update

Psoriatic arthritis (PsA) is a systemic inflammatory condition characterised by multiple clinical manifestations. Over the last decade, significant progress has been made in understanding the pathobiology of the disease. An expanded set of targeted therapies have emerged and have shown efficacy in PsA. Nevertheless, there is still a substantial subset of patients who experience no response or only a partial response to currently licensed therapies. The heterogeneous nature of the disease, together with a varying level of severity at presentation and disease activity during follow-up, brings tremendous challenges to devising management strategies. While there are certain pathophysiological similarities between PsA and rheumatoid arthritis (RA), it has become clear that there are discriminating features between these two conditions at the clinical, cellular, and molecular levels. However, there is a degree of overlap in the clinical approach when treating both PsA and RA, given that many biological and targeted therapies have proven efficacy for both pathologies. With an increasing understanding of the relevance of the IL-23/IL-17 axis in PsA, pharmacological agents blocking this pathway have provided promising possibilities for patients with PsA.

The transcriptional regulator Sin3A balances IL-17A and Foxp3 expression in primary CD4 T cells

The Sin3 transcriptional regulator homolog A (Sin3A) is the core member of a multiprotein chromatin-modifying complex. Its inactivation at the CD4/CD8 double-negative stage halts further thymocyte development. Among various functions, Sin3A regulates STAT3 transcriptional activity, central to the differentiation of Th17 cells active in inflammatory disorders and opportunistic infections. To further investigate the consequences of conditional Sin3A inactivation in more mature precursors and post-thymic T cell, we have generated CD4-Cre and CD4-CreER^T2 Sin3A^F/F mice. Sin3A inactivation in vivo hinders both thymocyte development and peripheral T-cell survival. In vitro, in Th17 skewing conditions, Sin3A-deficient cells proliferate and acquire memory markers and yet fail to properly upregulate Il17a, Il23r, and Il22. Instead, IL-2⁺ and FOXP3⁺ are mostly enriched for, and their inhibition partially rescues IL-17A⁺ T cells. Notably, Sin3A deletion also causes an enrichment of genes implicated in the mTORC1 signaling pathway, overt STAT3 activation, and aberrant cytoplasmic RORγt accumulation. Thus, together our data unveil a previously unappreciated role for Sin3A in shaping critical signaling events central to the acquisition of immunoregulatory T-cell phenotypes.

Neutrophils in Mycobacterium tuberculosis

Mycobacterium tuberculosis (M. tb) continues to be a leading cause of mortality within developing countries. The BCG vaccine to promote immunity against M. tb is widely used in developing countries and only in specific circumstances within the United States. However, current the literature reports equivocal data on the efficacy of the BCG vaccine. Critical within their role in the innate immune response, neutrophils serve as one of the first responders to infectious pathogens such as M. tb. Neutrophils promote effective clearance of M. tb through processes such as phagocytosis and the secretion of destructive granules. During the adaptative immune response, neutrophils modulate communication with lymphocytes to promote a strong pro-inflammatory response and to mediate the containment M. tb through the production of granulomas. In this review, we aim to highlight and summarize the role of neutrophils during an M. tb infection. Furthermore, the authors emphasize the need for more studies to be conducted on effective vaccination against M. tb.

The Role of Neutrophils in Spondyloarthritis: A Journey across the Spectrum of Disease Manifestations

Spondyloarthritis (SpA) contemplates the inflammatory involvement of the musculoskeletal system, gut, skin, and eyes, delineating heterogeneous diseases with a common pathogenetic background. In the framework of innate and adaptive immune disruption in SpA, neutrophils are arising, across different clinical domains, as pivotal cells crucial in orchestrating the pro-inflammatory response, both at systemic and tissue levels. It has been suggested they act as key players along multiple stages of disease trajectory fueling type 3 immunity, with a significant impact in the initiation and amplification of inflammation as well as in structural damage occurrence, typical of long-standing disease. The aim of our review is to focus on neutrophils' role within the spectrum of SpA, dissecting their functions and abnormalities in each of the relevant disease domains to understand their rising appeal as potential biomarkers and therapeutic targets.

Remodeling and Restraining Lung Tissue Damage Through the Regulation of Respiratory Immune Responses

Tissue damage caused by various stimuli under certain conditions, such as biological and environmental cues, can actively induce systemic and/or local immune responses. Therefore, understanding the immunological perspective would be critical to not only regulating homeostasis of organs and tissues but also to restrict and remodel their damage. Lungs serve as one of the key immunological organs, and thus, in the present article, we focus on the innate and adaptive immune systems involved in remodeling and engineering lung tissue. Innate immune cells are known to react immediately to damage. Macrophages, one of the most widely studied types of innate immune cells, are known to be involved in tissue damage and remodeling, while type 2 innate lymphoid cells (ILC2s) have recently been revealed as an important cell type responsible for tissue remodeling. On the other hand, adaptive immune cells are also involved in damage control. In particular, resident memory T cells in the lung prevent prolonged disease that causes tissue damage. In this review, we first outlined the structure of the respiratory system with biological and environmental cues and the innate/adaptive immune responses in the lung. It is our hope that understanding an immunological perspective for tissue remodeling and damage control in the lung will be beneficial for stakeholders in this area.

Interleukin-17 Promotes the Infiltration of CD8+ T Cells into the Brain in a Mouse Model for Alzheimer's Disease

BACKGROUND

Interleukin-17 (IL-17) family cytokines play critical roles in inflammation and pathogen resistance. Inflammation in the central nervous system, denoted as neuroinflammation, promotes the onset and progression of Alzheimer's disease (AD). Previous studies showed that IL-17A neutralizing antibody treatment alleviated Amyloid β (Aβ) burden in rodent models of AD, while overexpression of IL-17A in mouse lateral ventricles rescued part of the AD pathology. However, the involvement of IL-17 in AD and its mechanism of action remain largely unknown.

METHODS

To investigate the role of IL-17 in AD, we crossed mice lacking the common receptor of IL-17 signaling (IL-17RA knockout mice) to the APP/PS1 mouse model of AD. We then analyzed the composition of immune cells and cytokines/chemokines during different phases of AD pathology, and interrogated the underlying mechanism by which IL-17 may regulate immune cell infiltration into AD brains.

RESULTS

Ablation of IL-17RA in APP/PS1 mice decreased infiltration of CD8+ T cells and myeloid cells to mouse brain. IL-17 was able to promote the production of myeloid- and T cell-attracting chemokines CXCL1 and CXCL9/10 in primary glial cells. We also observed that IL-17 is upregulated in the late stage of AD development, and ectopic expression of IL-17 via adenoviral infection to the cortex trended towards worsened cognition in APP/PS1 mice, suggesting a pathogenic role of excessive IL-17 in AD.

CONCLUSION

Our data show that IL-17 signaling promotes neuroinflammation in AD by accelerating the infiltration of CD8+ T lymphocytes and Gr1+ CD11b+ myeloid cells.

Acinetobacter baumannii reinforces the pathogenesis by promoting IL-17 production in a mouse pneumonia model

Interleukin-17 (IL-17) is involved in host defense against bacterial infection. Little is known about the role of IL-17 in A. baumannii-infected pneumonia. Our objective was to investigate the role of IL-17 in pulmonary A. baumannii infection in a mouse model. We infected C57BL/6 mice intra-tracheally (i.t.) with A. baumannii to establish pneumonia model and found A. baumannii infection elevated IL-17 expression in lungs. IL-17-deficient (Il17^-/-) mice were resistant to pulmonary A. baumannii infection, showing improved mice survival, reduced bacteria burdens, and alleviated lung inflammation. Further, treatment of A. baumannii-infected Il17^-/- mice with IL-17 exacerbated the severity of pneumonia. These data suggest a pathogenic role of IL-17 in pulmonary A. baumannii infection. Further, the infiltration and phagocytic function of neutrophils in broncho-alveolar lavage fluid were detected by flow cytometry. The results showed that Il17^-/- mice had increased neutrophil infiltration and enhanced phagocytosis in neutrophils at the early time of infection. Treatment of mice with IL-17 suppressed phagocytic function of neutrophils. All data suggest that IL-17 promotes susceptibility of mice to pulmonary A. baumannii infection by suppressing neutrophil phagocytosis at early time of infection. Targeting IL-17 might be a potential therapeutic strategy in controlling the outcome of A. baumannii pneumonia.

The involvement of TH17 cells in the pathogenesis of IBD

The pathogenesis of inflammatory bowel disease (IBD) is still unclear. Immune dysfunction may play a key role in the pathogenesis of IBD, in which the role of CD4⁺ T helper (Th) cells is particularly important. Th17 cells are a major component of CD4⁺ T cells, and their differentiation is regulated by a variety of extracellular signals, transcription factors, RNA, and posttranslational modifications. Th17 cells specifically produce IL-17 and play an important role in the protection of mucous membranes and epithelial tissues against infection by extracellular microbes. However, when immune regulation is dysfunctional, Th17 cells abnormally proliferate and produce large amounts of proinflammatory cytokines that can recruit other inflammatory cells, which together induce abnormal immune responses and result in the development of many autoimmune diseases. In recent years, studies have confirmed that Th17 cells play an important role in the pathogenesis of IBD, which makes it a possible target for IBD therapy. This article reviews the recent progress of Th17 cells involved in the pathogenesis of IBD and its targeted therapy.

CD4 T-Cell Subsets and the Pathophysiology of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an umbrella term for the chronic immune-mediated idiopathic inflammation of the gastrointestinal tract, manifesting as Crohn's disease (CD) or ulcerative colitis (UC). IBD is characterized by exacerbated innate and adaptive immunity in the gut in association with microbiota dysbiosis and the disruption of the intestinal barrier, resulting in increased bacterial exposure. In response to signals from microorganisms and damaged tissue, innate immune cells produce inflammatory cytokines and factors that stimulate T and B cells of the adaptive immune system, and a prominent characteristic of IBD patients is the accumulation of inflammatory T-cells and their proinflammatory-associated cytokines in intestinal tissue. Upon antigen recognition and activation, CD4 T-cells differentiate towards a range of distinct phenotypes: T helper(h)1, Th2, Th9, Th17, Th22, T follicular helper (Tfh), and several types of T-regulatory cells (Treg). T-cells are generated according to and adapt to microenvironmental conditions and participate in a complex network of interactions among other immune cells that modulate the further progression of IBD. This review examines the role of the CD4 T-cells most relevant to IBD, highlighting how these cells adapt to the environment and interact with other cell populations to promote or inhibit the development of IBD.

Bystander activation of Bordetella pertussis-induced nasal tissue-resident memory CD4 T cells confers heterologous immunity to Klebsiella pneumoniae

Tissue-resident memory CD4 T (T_RM ) cells induced by infection with Bordetella pertussis persist in respiratory tissues and confer long-term protective immunity against reinfection. However, it is not clear how they are maintained in respiratory tissues. Here, we demonstrate that B. pertussis-specific CD4 T_RM cells produce IL-17A in response to in vitro stimulation with LPS or heat-killed Klebsiella pneumoniae (HKKP) in the presence of dendritic cells. Furthermore, IL-17A-secreting CD4 T_RM cells expand in the lung and nasal tissue of B. pertussis convalescent mice following in vivo administration of LPS or HKKP. Bystander activation of CD4 T_RM cells was suppressed by anti-IL-12p40 but not by anti-MHCII antibodies. Furthermore, purified respiratory tissue-resident, but not circulating, CD4 T cells from convalescent mice produced IL-17A following direct stimulation with IL-23 and IL-1β or IL-18. Intranasal immunization of mice with a whole-cell pertussis vaccine induced respiratory CD4 T_RM cells that were reactivated following stimulation with K. pneumoniae. Furthermore, the nasal pertussis vaccine conferred protective immunity against B. pertussis but also attenuated infection with K. pneumoniae. Our findings demonstrate that CD4 T_RM cells induced by respiratory infection or vaccination can undergo bystander activation and confer heterologous immunity to an unrelated respiratory pathogen.

IL-17 and IL-17-producing cells in protection versus pathology

IL-17 cytokine family members have diverse biological functions, promoting protective immunity against many pathogens but also driving inflammatory pathology during infection and autoimmunity. IL-17A and IL-17F are produced by CD4⁺ and CD8⁺ T cells, γδ T cells, and various innate immune cell populations in response to IL-1β and IL-23, and they mediate protective immunity against fungi and bacteria by promoting neutrophil recruitment, antimicrobial peptide production and enhanced barrier function. IL-17-driven inflammation is normally controlled by regulatory T cells and the anti-inflammatory cytokines IL-10, TGFβ and IL-35. However, if dysregulated, IL-17 responses can promote immunopathology in the context of infection or autoimmunity. Moreover, IL-17 has been implicated in the pathogenesis of many other disorders with an inflammatory basis, including cardiovascular and neurological diseases. Consequently, the IL-17 pathway is now a key drug target in many autoimmune and chronic inflammatory disorders; therapeutic monoclonal antibodies targeting IL-17A, both IL-17A and IL-17F, the IL-17 receptor, or IL-23 are highly effective in some of these diseases. However, new approaches are needed to specifically regulate IL-17-mediated immunopathology in chronic inflammation and autoimmunity without compromising protective immunity to infection.

Th17 Cells: Orchestrators of Mucosal Inflammation and Potential Therapeutic Targets

T helper 17 (Th17) cells represent a specialized subgroup of effector CD4+ T cells known for their role in provoking neutrophil-driven tissue inflammation, particularly within mucosal tissues. Although they are pivotal for defending the host against extracellular bacteria and fungi, they have also been associated with development of various T cell-mediated inflammatory conditions, autoimmune diseases, and even cancer. Notably, Th17 cells exhibit a dual nature, with different Th17 cell subtypes showcasing distinct effector functions and varying capacities to incite autoimmune tissue inflammation. Furthermore, Th17 cells exhibit significant plasticity, which carries important functional implications, both in terms of their expression of cytokines typically associated with other effector T cell subsets and in their interactions with regulatory CD4+ T cells. The intricate balance of Th17 cytokines can also be a double-edged sword in inflammation, autoimmunity, and cancer. Within this article, we delve into the mechanisms that govern the differentiation, function, and adaptability of Th17 cells. We culminate with an exploration of therapeutic potentials in harnessing the power of Th17 cells and their cytokines. Targeted interventions to modulate Th17 responses are emerging as promising strategies for autoimmunity, inflammation, and cancer treatment. By precisely fine-tuning Th17-related pathways, we may unlock new avenues for personalized therapeutic approaches, aiming to restore immune balance, alleviate the challenges of these disorders, and ultimately enhance the quality of life for individuals affected by them.

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

The role of γδ T17 cells in cardiovascular disease

Due to the ability of γδ T cells to bridge adaptive and innate immunity, γδ T cells can respond to a variety of molecular cues and acquire the ability to induce a variety of cytokines such as IL-17 family, IFN-γ, IL-4, and IL-10. IL-17⁺ γδ T cells (γδ T17 cells) populations have recently received considerable interest as they are the major early source of IL-17A in many immune response models. However, the exact mechanism of γδ T17 cells is still poorly understood, especially in the context of cardiovascular disease (CVD). CVD is the leading cause of death in the world, and it tends to be younger. Here, we offer a review of the cardiovascular inflammatory and immune functions of γδ T17 cells in order to understand their role in CVD, which may be the key to developing new clinical applications.