Synovial IL-9 facilitates neutrophil survival, function and differentiation of Th17 cells in rheumatoid arthritis

Unveiling Novel Drug Targets and Emerging Therapies for Rheumatoid Arthritis: A Comprehensive Review

Rheumatoid arthritis (RA) is a chronic debilitating autoimmune disease, that causes joint damage, deformities, and decreased functionality. In addition, RA can also impact organs like the skin, lungs, eyes, and blood vessels. This autoimmune condition arises when the immune system erroneously targets the joint synovial membrane, resulting in synovitis, pannus formation, and cartilage damage. RA treatment is often holistic, integrating medication, physical therapy, and lifestyle modifications. Its main objective is to achieve remission or low disease activity by utilizing a "treat-to-target" approach that optimizes drug usage and dose adjustments based on clinical response and disease activity markers. The primary RA treatment uses disease-modifying antirheumatic drugs (DMARDs) that help to interrupt the inflammatory process. When there is an inadequate response, a combination of biologicals and DMARDs is recommended. Biological therapies target inflammatory pathways and have shown promising results in managing RA symptoms. Close monitoring for adverse effects and disease progression is critical to ensure optimal treatment outcomes. A deeper understanding of the pathways and mechanisms will allow new treatment strategies that minimize adverse effects and maintain quality of life. This review discusses the potential targets that can be used for designing and implementing precision medicine in RA treatment, spotlighting the latest breakthroughs in biologics, JAK inhibitors, IL-6 receptor antagonists, TNF blockers, and disease-modifying noncoding RNAs.

The emerging role of T helper 9 (Th9) cells in immunopathophysiology: A comprehensive review of their effects and responsiveness in various disease states

Th9 cells, a subset of T-helper cells producing interleukin-9 (IL-9), play a vital role in the adaptive immune response and have diverse effects in different diseases. Regulated by transcription factors like PU.1 and IRF4, and cytokines such as IL-4 and TGF-β, Th9 cells drive tissue inflammation. This review focuses on their emerging role in immunopathophysiology. Th9 cells exhibit immune-mediated cancer cell destruction, showing promise in glioma and cervical cancer treatment. However, their role in breast and lung cancer is intricate, requiring a deeper understanding of pro- and anti-tumor aspects. Th9 cells, along with IL-9, foster T cell and immune cell proliferation, contributing to autoimmune disorders. They are implicated in psoriasis, atopic dermatitis, and infections. In allergic reactions and asthma, Th9 cells fuel pro-inflammatory responses. Targeting Foxo1 may regulate innate and adaptive immune responses, alleviating disease symptoms. This comprehensive review outlines Th9 cells' evolving immunopathophysiological role, emphasizing the necessity for further research to grasp their effects and potential therapeutic applications across diseases.

Exercise and osteoimmunology in bone remodeling

Bones can form the scaffolding of the body, support the organism, coordinate somatic movements, and control mineral homeostasis and hematopoiesis. The immune system plays immune supervisory, defensive, and regulatory roles in the organism, which mainly consists of immune organs (spleen, bone marrow, tonsils, lymph nodes, etc.), immune cells (granulocytes, platelets, lymphocytes, etc.), and immune molecules (immune factors, interferons, interleukins, tumor necrosis factors, etc.). Bone and the immune system have long been considered two distinct fields of study, and the bone marrow, as a shared microenvironment between the bone and the immune system, closely links the two. Osteoimmunology organically combines bone and the immune system, elucidates the role of the immune system in bone, and creatively emphasizes its interdisciplinary characteristics and the function of immune cells and factors in maintaining bone homeostasis, providing new perspectives for skeletal-related field research. In recent years, bone immunology has gradually become a hot spot in the study of bone-related diseases. As a new branch of immunology, bone immunology emphasizes that the immune system can directly or indirectly affect bones through the RANKL/RANK/OPG signaling pathway, IL family, TNF-α, TGF-β, and IFN-γ. These effects are of great significance for understanding inflammatory bone loss caused by various autoimmune or infectious diseases. In addition, as an external environment that plays an important role in immunity and bone, this study pays attention to the role of exercise-mediated bone immunity in bone reconstruction.

Increased interleukin-9 and Th9 cells in patients with refractory Graves' disease and interleukin-9 polymorphisms are associated with autoimmune thyroid diseases

Introduction

Autoimmune thyroid diseases (AITDs) are prevalent disorders, primarily encompassing Graves' disease (GD) and Hashimoto's thyroiditis (HT). Despite their common occurrence, the etiology of AITDs remains elusive. Th9 cells, a new subset of CD4+T cells with immunomodulatory properties, have been linked to the development of various autoimmune diseases. However, research on the role of Th9 cells in AITDs is limited.

Methods

We investigated the expression of Th9 cells,their functional cytokine IL-9, and transcription factor IRF4 in peripheral blood mononuclear cells (PBMCs) and plasma of AITD patients and healthy controls. Additionally, we explored the genetic association between four loci polymorphisms (rs31564, rs2069879, rs1859430, and rs2069868) of the IL-9 gene and AITDs.

Results

We reported, for the first time, that refractory GD patients exhibited elevated mRNA levels of IL-9 and IRF4 in PBMCs, increased IL-9 protein levels in plasma, and a higher proportion of Th9 cells in peripheral blood when compared to normal controls. Furthermore, human recombinant IL-9 protein was found to enhance IFN-g secretion in PBMCs from both GD patients and normal controls. At the genetic association level, after adjusting for age and sex, the rs2069879 polymorphism exhibited a significant association with AITDs under an additive model (P<0.001, OR= 0.05, 95% CI=0.03-0.08).

Discussion

Our results reveal that Th9 cells may exert a pivotal role in the pathogenesis and progression of refractory GD and HT, and IL-9 holds promise as a novel therapeutic target for the management of AITDs.

Regulatory role of T helper 9/interleukin-9: Transplantation view

T helper 9 (Th9) cells, a subset of CD4+ T helper cells, have emerged as a valuable target for immune cell therapy due to their potential to induce immunomodulation and tolerance. The Th9 cells mainly produce interleukin (IL)-9 and are known for their defensive effects against helminth infections, allergic and autoimmune responses, and tumor suppression. This paper explores the mechanisms involved in the generation and differentiation of Th9 cells, including the cytokines responsible for their polarization and stabilization, the transcription factors necessary for their differentiation, as well as the role of Th9 cells in inflammatory and autoimmune diseases, allergic reactions, and cancer immunotherapies. Recent research has shown that the differentiation of Th9 cells is coregulated by the transcription factors transforming growth factor β (TGF-β), IL-4, and PU.1, which are also known to secrete IL-10 and IL-21. Multiple cell types, such as T and B cells, mast cells, and airway epithelial cells, are influenced by IL-9 due to its pleiotropic effects.

Negative impact of Interleukin-9 on synovial regulatory T cells in rheumatoid arthritis

In Rheumatoid Arthritis (RA), regulatory T cells (Tregs) have been found to be enriched in the synovial fluid. Despite their accumulation, they are unable to suppress synovial inflammation. Recently, we showed the synovial enrichment of interleukin-9 (IL-9) producing helper T cells and its positive correlation with disease activity. Therefore, we investigated the impact of IL-9 on synovial Tregs in RA. Here, we confirmed high synovial Tregs in RA patients, however these cells were functionally impaired in terms of suppressive cytokine production (IL-10 and TGF-β). Abrogating IL-9/ IL-9 receptor interaction could restore the suppressive cytokine production of synovial Tregs and reduce the synovial inflammatory T cells producing IFN-γ, TNF-α, IL-17. However, blocking these inflammatory cytokines failed to show any effect on IL-9 producing T cells, highlighting IL-9's hierarchy in the inflammatory network. Thus, we propose that blocking IL-9 might dampen synovial inflammation by restoring Tregs function and inhibiting inflammatory T cells.

The local microenvironment drives activation of neutrophils in human brain tumors

Neutrophils are abundant immune cells in the circulation and frequently infiltrate tumors in substantial numbers. However, their precise functions in different cancer types remain incompletely understood, including in the brain microenvironment. We therefore investigated neutrophils in tumor tissue of glioma and brain metastasis patients, with matched peripheral blood, and herein describe the first in-depth analysis of neutrophil phenotypes and functions in these tissues. Orthogonal profiling strategies in humans and mice revealed that brain tumor-associated neutrophils (TANs) differ significantly from blood neutrophils and have a prolonged lifespan and immune-suppressive and pro-angiogenic capacity. TANs exhibit a distinct inflammatory signature, driven by a combination of soluble inflammatory mediators including tumor necrosis factor alpha (TNF-ɑ) and Ceruloplasmin, which is more pronounced in TANs from brain metastasis versus glioma. Myeloid cells, including tumor-associated macrophages, emerge at the core of this network of pro-inflammatory mediators, supporting the concept of a critical myeloid niche regulating overall immune suppression in human brain tumors.

Elevated serum IL-36γ levels in patients with ankylosing spondylitis and its association with disease activity

Ankylosing spondylitis (AS) is a chronic autoimmune disease. The purpose of this study was to investigate the levels of serum IL-36γ in AS patients and their association with AS. The study enrolled 131 subjects, including 45 with active AS, 46 with inactive AS, and 40 healthy controls (HCs). The basic clinical information of each participant was obtained through physical examination and relevant clinical medical records. Serum IL-36γ levels were detected through an enzyme-linked immunosorbent assay. Serum IL-36γ levels in the active AS group were significantly higher than those in the HC group (94.72 vs. 65.76 pg/mL, P = 0.0087). The serum IL-36γ concentration in the inactive AS group was increased as compared to that in the HC group (100.90 vs. 65.76 pg/mL, P = 0.0138). Correlation analysis indicated that serum IL-36γ was positively correlated with glutamyl transferase in the active AS group (P = 0.0172), while serum IL-36γ was positively correlated with uric acid in the inactive AS group (P = 0.0151). The area under the curve (AUC) for IL-36γ was 0.6824 (P = 0.0009), and the AUC for IL-36γ combined with the erythrocyte sedimentation rate and C-reactive protein levels was 0.8102 (P < 0.0001), according to receiver operating characteristic curve analysis. This study found that serum IL-36γ levels were elevated in AS patients and correlated with disease activity. Our results suggest that IL-36γ may be involved in the progression of AS disease and is a potential biomarker for AS.

Mechanistic insight of interleukin-9 induced osteoclastogenesis

Interleukin (IL)-9 is an emerging player in the pathogenesis of various chronic inflammatory diseases including bone disorders like rheumatoid arthritis (RA) and psoriatic arthritis. Recently, IL-9 was shown to enhance the osteoclast formation and their function in RA. However, the mechanisms by which IL-9 influences osteoclastogenesis are not known. Therefore, in this study we aimed to unravel the direct and indirect ways by which IL-9 can influence osteoclast formation. We used mouse bone marrow precursor cells for checking the effect of IL-9 on osteoclast differentiation and its function. Next, IL-9 induced signalling pathway were checked in the process of osteoclastogenesis. T cells play an important role in enhancing osteoclastogenesis in inflammatory conditions. We used splenic T cells to understand the impact of IL-9 on the functions of T effector (Teff) and regulatory T (Treg) cells. Furthermore, the effect of IL-9 mediated modulation of the T cell response on osteoclasts was checked using a coculture model of T cells with osteoclast precursors. We showed that IL-9 enhanced osteoclast formation and its function. We found that IL-9 activates STAT3, P38 MAPK, ERK1/2, NFκB and we hypothesize that it mediates the effect on osteoclastogenesis by accelerating mitochondrial biogenesis. Additionally, IL-9 was observed to facilitate the functions of pro-osteoclastogenic IL-17 producing T cells, but inhibits the function of anti-osteoclastogenic Treg cells. Our observations suggest that IL-9 can influence osteoclastogenesis directly by modulating the signalling cascade in the precursor cells; indirectly by enhancing IL-17 producing T cells and by reducing the functions of Treg cells.

T cells in health and disease

T cells are crucial for immune functions to maintain health and prevent disease. T cell development occurs in a stepwise process in the thymus and mainly generates CD4⁺ and CD8⁺ T cell subsets. Upon antigen stimulation, naïve T cells differentiate into CD4⁺ helper and CD8⁺ cytotoxic effector and memory cells, mediating direct killing, diverse immune regulatory function, and long-term protection. In response to acute and chronic infections and tumors, T cells adopt distinct differentiation trajectories and develop into a range of heterogeneous populations with various phenotype, differentiation potential, and functionality under precise and elaborate regulations of transcriptional and epigenetic programs. Abnormal T-cell immunity can initiate and promote the pathogenesis of autoimmune diseases. In this review, we summarize the current understanding of T cell development, CD4⁺ and CD8⁺ T cell classification, and differentiation in physiological settings. We further elaborate the heterogeneity, differentiation, functionality, and regulation network of CD4⁺ and CD8⁺ T cells in infectious disease, chronic infection and tumor, and autoimmune disease, highlighting the exhausted CD8⁺ T cell differentiation trajectory, CD4⁺ T cell helper function, T cell contributions to immunotherapy and autoimmune pathogenesis. We also discuss the development and function of γδ T cells in tissue surveillance, infection, and tumor immunity. Finally, we summarized current T-cell-based immunotherapies in both cancer and autoimmune diseases, with an emphasis on their clinical applications. A better understanding of T cell immunity provides insight into developing novel prophylactic and therapeutic strategies in human diseases.

Interleukin 26 Induces Macrophage IL-9 Expression in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an autoimmune disease with chronic inflammation, bone erosion, and joint deformation. Synovial tissue in RA patients is full of proinflammatory cytokines and infiltrated immune cells, such as T help (Th) 9, Th17, macrophages, and osteoclasts. Recent reports emphasized a new member of the interleukin (IL)-10 family, IL-26, an inducer of IL-17A that is overexpressed in RA patients. Our previous works found that IL-26 inhibits osteoclastogenesis and conducts monocyte differentiation toward M1 macrophages. In this study, we aimed to clarify the effect of IL-26 on macrophages linking to Th9 and Th17 in IL-9 and IL-17 expression and downstream signal transduction. Murine and human macrophage cell lines and primary culture cells were used and stimulated by IL26. Cytokines expressions were evaluated by flow cytometry. Signal transduction and transcription factors expression were detected by Western blot and real time-PCR. Our results show that IL-26 and IL-9 colocalized in macrophage in RA synovium. IL-26 directly induces macrophage inflammatory cytokines IL-9 and IL-17A expression. IL-26 increases the IL-9 and IL-17A upstream mechanisms IRF4 and RelB expression. Moreover, the AKT-FoxO1 pathway is also activated by IL-26 in IL-9 and IL-17A expressing macrophage. Blockage of AKT phosphorylation enhances IL-26 stimulating IL-9-producing macrophage cells. In conclusion, our results support that IL-26 promotes IL-9- and IL-17-expressing macrophage and might initiate IL-9- and IL-17-related adaptive immunity in rheumatoid arthritis. Targeting IL-26 may a potential therapeutic strategy for rheumatoid arthritis or other IL-9 plus IL-17 dominant diseases.

Simiao Yong'an decoction ameliorates murine collagen-induced arthritis by modulating neutrophil activities: An in vitro and in vivo study

ETHNOPHARMACOLOGICAL RELEVANCE

Rheumatoid arthritis (RA) is a common systemic autoimmune disease with high morbidity and disability rate. Currently, there is no effective allopathic treatment for RA, and most of the drugs provoke many adverse effects. Simiao Yong'an decoction (SMYAD) is a traditional Chinese prescription for the treatment of sore and gangrene caused by hot poison. With the development of pharmacology and clinical research, SMYAD has remarkable anti-inflammatory properties and has been used for RA treatments for years.

AIM OF THE STUDY

This study aimed to investigate the anti-arthritic effect of SMYAD and further explore the immunopharmacological mechanisms.

MATERIALS AND METHODS

Arthritis was induced in DBA/1 mice by two-time immunizations. Collagen-induced rheumatoid arthritis (CIA) mice were divided into 4 groups: control, model, methotrexate (MTX), and SMYAD group (n = 6). The administration groups were given MTX (0.5 mg/kg/3 d) and SMYAD (4.5 g/kg/d) by gavage from day 14. The arthritis index (AI) score was evaluated every 3 days after the second immunization. Hematoxylin and eosin (H&E) staining, Safranin-O fast green staining, Trap staining, and Micro-CT were used to measure the histopathology injuries and bone destruction of joints. Granulocyte changes in the spleen, bone marrow, and period blood were analyzed by flow cytometry. The expression of inflammatory cytokines and chemokines in joints were detected by qRT-PCR. SMYAD-containing serum was obtained from SD rats gavaged with SMYAD. Neutrophils were isolated from peripheral blood and bone marrow for the in vitro experiments of transwell cell assay, apoptosis assay, reactive oxygen species (ROS) generation and neutrophil extracellular traps (NETs) formation.

RESULTS

SMYAD significantly relieved arthritis severity in CIA mice. The AI score was significantly decreased in the SMYAD group compared with the model group. Additionally, SMYAD alleviated inflammatory infiltration, cartilage damage, osteoclast formation, and bone damage in the ankle joints. In the flow cytometry assay, SMYAD significantly reduced granulocytes number in the spleen and bone marrow, while increased in peripheral blood. Furthermore, compared with the CIA group, SMYAD suppressed the mRNA levels of inflammatory factors including TNF-α, IL-1β, IL-6 and chemokines CXCL1, CXCL2, and IL-8 in the inflamed joints. In the in vitro studies, 20% SMYAD-containing serum effectively inhibited the migration of neutrophils, promoted neutrophils apoptosis, reduced ROS production and NETs formation.

CONCLUSION

Collectively, our results demonstrated that SMYAD effectively restrained arthritis in CIA mice by modulating neutrophil activities.

Th2 Cytokines (Interleukin-5 and -9) Polymorphism Affects the Response to Anti-TNF Treatment in Polish Patients with Ankylosing Spondylitis

Ankylosing spondylitis (AS) is an inflammatory disease that belongs to the spondyloarthritis family. IL-5 and IL-9 belong to the group of Th2 cytokines of anti-inflammatory nature. Polymorphisms in their coding genes have been so far associated with various inflammatory diseases, but there are no reports regarding their involvement in AS pathogenesis to date. The purpose of the study was to investigate relationships between IL5 and IL9 genetic variants with AS susceptibility, clinical parameters as well as response to therapy with TNF inhibitors. In total 170 patients receiving anti-TNF therapy and 218 healthy controls were enrolled in the study. The genotyping of IL5 rs2069812 (A > G) and IL9 rs2069885 (G > A) single nucleotide polymorphisms was performed using the Real-Time PCR method based on LightSNiP kits assays. The present study demonstrated significant relationships between IL5 rs2069812 and IL9 rs2069885 polymorphisms and response to anti-TNF therapy. Presence of the IL5 rs2069812 A allele in patients positively correlated with better response to treatment (p = 0.022). With regard to IL9 rs2069885, patients carrying the A allele displayed better outcomes in anti-TNF therapy (p = 0.046). In addition, IL5 rs2069812 A and IL9 rs2069885 A alleles were associated with lower CRP and VAS values. The obtained results may indicate a significant role for IL-5 and IL-9 in the course of AS and response to anti-TNF therapy.

Exploiting the role of T cells in the pathogenesis of Sjögren's syndrome for therapeutic treatment

Sjögrens syndrome (SS) is caused by autoantibodies that attack proprioceptive salivary and lacrimal gland tissues. Damage to the glands leads to dry mouth and eyes and affects multiple systems and organs. In severe cases, SS is life-threatening because it can lead to interstitial lung disease, renal insufficiency, and lymphoma. Histological examination of the labial minor salivary glands of patients with SS reveals focal lymphocyte aggregation of T and B cells. More studies have been conducted on the role of B cells in the pathogenesis of SS, whereas the role of T cells has only recently attracted the attention of researchers. This review focusses on the role of various populations of T cells in the pathogenesis of SS and the progress made in research to therapeutically targeting T cells for the treatment of patients with SS.

The role of a key transcription factor PU.1 in autoimmune diseases

PU.1, a transcription factor member of the E26 transformation-specific family, affects the function of a variety of immune cells in several physiological and pathological conditions. Previous studies studying the role of PU.1 in pathological conditions have mainly focused on immune system-related cancers, and a series of articles have confirmed that PU.1 mutation can induce a variety of immune cell-related malignancies. The underlying mechanism has also been extensively validated. However, the role of PU.1 in other major immune system-related diseases, namely, systemic autoimmune diseases, is still unclear. It was only in recent years that researchers began to gradually realize that PU.1 also played an important role in a variety of autoimmune diseases, such as rheumatoid arthritis (RA), experimental autoimmune encephalomyelitis (EAE) and systemic lupus erythematosus (SLE). This review article summarizes the findings of recent studies that investigated the role of PU.1 in various autoimmune diseases and the related underlying mechanisms. Furthermore, it presents new ideas and provides insight into the role of PU.1 as a potential treatment target for autoimmune diseases and highlights existing research problems and future research directions in related fields.

Migration and homeostasis of regulatory T cells in rheumatoid arthritis

Regulatory T (T_reg) cells are garnering increased attention in research related to autoimmune diseases, including rheumatoid arthritis (RA). They play an essential role in the maintenance of immune homeostasis by restricting effector T cell activity. Reduced functions and frequencies of T_reg cells contribute to the pathogenesis of RA, a common autoimmune disease which leads to systemic inflammation and erosive joint destruction. T_reg cells from patients with RA are characterized by impaired functions and by an altered phenotype. They show increased plasticity towards Th17 cells and a reduced suppressive capacity. Besides the suppressive function of T_reg cells, their effectiveness is determined by their ability to migrate into inflamed tissues. In the past years, new mechanisms involved in T_reg cell migration have been identified. One example of such a mechanism is the phosphorylation of vasodilator-stimulated phosphoprotein (VASP). Efficient migration of T_reg cells requires the presence of VASP. IL-6, a cytokine which is abundantly present in the peripheral blood and in the synovial tissue of RA patients, induces posttranslational modifications of VASP. Recently, it has been shown in mice with collagen-induced arthritis (CIA) that this IL-6 mediated posttranslational modification leads to reduced T_reg cell trafficking. Another protein which facilitates T_reg cell migration is G-protein-signaling modulator 2 (GPSM2). It modulates G-protein coupled receptor functioning, thereby altering the cellular activity initiated by cell surface receptors in response to extracellular signals. The almost complete lack of GPSM2 in T_reg cells from RA patients contributes to their reduced ability to migrate towards inflammatory sites. In this review article, we highlight the newly identified mechanisms of T_reg cell migration and review the current knowledge about impaired T_reg cell homeostasis in RA.

Metabolic Profiling of Rheumatoid Arthritis Neutrophils Reveals Altered Energy Metabolism That Is Not Affected by JAK Inhibition

Neutrophils play a key role in the pathophysiology of rheumatoid arthritis (RA) where release of ROS and proteases directly causes damage to joints and tissues. Neutrophil function can be modulated by Janus Kinase (JAK) inhibitor drugs, including tofacitinib and baricitinib, which are clinically effective treatments for RA. However, clinical trials have reported increased infection rates and transient neutropenia during therapy. The subtle differences in the mode of action, efficacy and safety of JAK inhibitors have been the primary research topic of many clinical trials and systematic reviews, to provide a more precise and targeted treatment to patients. The aim of this study was to determine both the differences in the metabolome of neutrophils from healthy controls and people with RA, and the effect of different JAK inhibitors on the metabolome of healthy and RA neutrophils. Isolated neutrophils from healthy controls (HC) (n = 6) and people with RA (n = 7) were incubated with baricitinib, tofacitinib or a pan-JAK inhibitor (all 200 ng/mL) for 2 h. Metabolites were extracted, and 1H nuclear magnetic resonance (NMR) was applied to study the metabolic changes. Multivariate analyses and machine learning models showed a divergent metabolic pattern in RA neutrophils compared to HC at 0 h (F1 score = 86.7%) driven by energy metabolites (ATP, ADP, GTP and glucose). No difference was observed in the neutrophil metabolome when treated with JAK inhibitors. However, JAK inhibitors significantly inhibited ROS production and baricitinib decreased NET production (p < 0.05). Bacterial killing was not impaired by JAK inhibitors, indicating that the effect of JAK inhibitors on neutrophils can inhibit joint damage in RA without impairing host defence. This study highlights altered energy metabolism in RA neutrophils which may explain the cause of their dysregulation in inflammatory disease.

The absence of IL-9 reduces allergic airway inflammation by reducing ILC2, Th2 and mast cells in murine model of asthma

Allergic asthma is an allergic inflammatory disease of the airways, in which numerous cell types and cytokines have been shown to contribute to pathogenesis of the disease. Although increased expression of IL-9 has been shown to influence the activity of structural as well as eosinophils and mast cells in asthma, the influence of IL-9 on function of ILC2 and Th2 cells remains unclear. This study therefore aimed to elucidate the role of IL-9 on ILC2 and Th2 cells using a murine model of asthma. A murine model of asthma was established using wild type (WT) and IL-9-deficient (Il9^−/−) transgenic mice sensitized to house dust mite (HDM). Bronchoalveolar lavage fluid (BALF) and lung tissues were collected, and analysed for inflammatory cells (eosinophils, mast cells, Th2 cells and ILC2 cells), histopathological changes, and several cytokines. HDM challenge significantly increased accumulation of ILC2 cells, Th2 cells and mast cells, as well as goblet cell hyperplasia, and the expression of cytokines IL-4, IL-5 and IL-13, but not IFN-γ, in WT mice compared to saline-challenged control group. In contrast, all pathological changes, including infiltration of ILC2 cells, Th2 cells and mast cells, were significantly attenuated in HDM-challenged Il9^−/− mice. Furthermore, the number of Ki67⁺ILC2 cells, Ki67⁺Th2 cells and Ki67⁺mast cells were significantly reduced in the absence of IL-9 signalling. These data suggest that IL-9 promotes the proliferation and type 2 cytokine production of type 2 cells in the murine models of asthma, and therefore might be a potential therapeutic target for asthma treatment.

The Interactions Between Autoinflammation and Type 2 Immunity: From Mechanistic Studies to Epidemiologic Associations

Autoinflammatory diseases are a group of clinical syndromes characterized by constitutive overactivation of innate immune pathways. This results in increased production of or responses to monocyte- and neutrophil-derived cytokines such as interleukin-1β (IL-1β), Tumor Necrosis Factor-α (TNF-α), and Type 1 interferon (IFN). By contrast, clinical allergy is caused by dysregulated type 2 immunity, which is characterized by expansion of T helper 2 (Th2) cells and eosinophils, as well as overproduction of the associated cytokines IL-4, IL-5, IL-9, and IL-13. Traditionally, type 2 immune cells and autoinflammatory effectors were thought to counter-regulate each other. However, an expanding body of evidence suggests that, in some contexts, autoinflammatory pathways and cytokines may potentiate type 2 immune responses. Conversely, type 2 immune cells and cytokines can regulate autoinflammatory responses in complex and context-dependent manners. Here, we introduce the concepts of autoinflammation and type 2 immunity. We proceed to review the mechanisms by which autoinflammatory and type 2 immune responses can modulate each other. Finally, we discuss the epidemiology of type 2 immunity and clinical allergy in several monogenic and complex autoinflammatory diseases. In the future, these interactions between type 2 immunity and autoinflammation may help to expand the spectrum of autoinflammation and to guide the management of patients with various autoinflammatory and allergic diseases.

The Neuroimmune Interplay in Joint Pain: The Role of Macrophages

Chronic pain associated with joint disorders, such as rheumatoid arthritis (RA), osteoarthritis (OA) and implant aseptic loosening (AL), is a highly debilitating symptom that impacts mobility and quality of life in affected patients. The neuroimmune crosstalk has been demonstrated to play a critical role in the onset and establishment of chronic pain conditions. Immune cells release cytokines and immune mediators that can activate and sensitize nociceptors evoking pain, through interaction with receptors in the sensory nerve terminals. On the other hand, sensory and sympathetic nerve fibers release neurotransmitters that bind to their specific receptor expressed on surface of immune cells, initiating an immunomodulatory role. Macrophages have been shown to be key players in the neuroimmune crosstalk. Moreover, macrophages constitute the dominant immune cell population in RA, OA and AL. Importantly, the targeting of macrophages can result in anti-nociceptive effects in chronic pain conditions. Therefore, the aim of this review is to discuss the nature and impact of the interaction between the inflammatory response and nerve fibers in these joint disorders regarding the genesis and maintenance of pain. The role of macrophages is highlighted. The alteration in the joint innervation pattern and the inflammatory response are also described. Additionally, the immunomodulatory role of sensory and sympathetic neurotransmitters is revised.

Epigenetically-regulated RPN2 gene influences lymphocyte activation and is involved in pathogenesis of rheumatoid arthritis

BACKGROUND

To identify RA-associated genes and to ascertain epigenetic factors and functional mechanisms underlying RA pathogenesis.

METHODS

Peripheral blood mononuclear cells (PBMC) transcriptome- and proteome- wide gene expressions were profiled in a case-control study sample. Differentially expressed genes (DEGs) were discovered and validated independently. In-house PBMC genome-wide SNP genotyping data, miRNA expression data and DNA methylation data in the same sample were utilized to identify SNPs [expression quantitative trait locus (eQTLs) and protein quantitative trait locus (pQTLs)], miRNAs, and DNA methylation positions (DMPs) regulating key DEG of interest. Lentivirus transfection was conducted to study the effects of RPN2 on T lymphocyte activation, proliferation, apoptosis, and inflammatory cytokine expression. Rpn2 protein level in plasma was quantitated by ELISA to assess its performance in discriminating RA cases and controls.

RESULTS

Twenty-two DEGs were discovered in PBMCs. The most significant DEG, i.e., RPN2, was validated to be up-regulated with RA in PBMCs. A complex regulatory network for RPN2 gene expression in PBMCs was constructed, which consists of 38 eQTL and 53 pQTL SNPs, 3 miRNAs and 2 DMPs. Besides, RPN2 expression was significantly up-regulated with RA in primary T lymphocytes, as well as in PHA-activated T lymphocytes. RPN2 over-expression in T lymphocytes significantly inhibited apoptosis and IL-4 expression and promoted proliferation and activation. PBMCs-expressed RPN2 mRNA and plasma Rpn2 protein demonstrated superior and modest performances in discriminating RA cases and controls, respectively.

CONCLUSIONS

RPN2 gene influences T lymphocyte growth and activation and is involved in the pathogenesis of RA. Rpn2 may serve as a novel protein biomarker for RA diagnosis.

Interleukin-9 Facilitates Osteoclastogenesis in Rheumatoid Arthritis

In rheumatoid arthritis (RA), inflammatory cytokines play a pivotal role in triggering abnormal osteoclastogenesis leading to articular destruction. Recent studies have demonstrated enhanced levels of interleukin-9 (IL-9) in the serum and synovial fluid of patients with RA. In RA, strong correlation has been observed between tissue inflammation and IL-9 expression in synovial tissue. Therefore, we investigated whether IL-9 influences osteoclastogenesis in patients with RA. We conducted the study in active RA patients. For inducing osteoclast differentiation, mononuclear cells were stimulated with soluble receptor activator of NF-kB ligand (sRANKL) and macrophage-colony-stimulating factor (M-CSF) in the presence or absence of recombinant (r) IL-9. IL-9 stimulation significantly enhanced M-CSF/sRANKL-mediated osteoclast formation and function. Transcriptome analysis revealed differential gene expression induced with IL-9 stimulation in the process of osteoclast differentiation. IL-9 mainly modulates the expression of genes, which are involved in the metabolic pathway. Moreover, we observed that IL-9 modulates the expression of matrix metalloproteinases (MMPs), which are critical players in bone degradation. Our results indicate that IL-9 has the potential to influence the structural damage in the RA by promoting osteoclastogenesis and modulating the expression of MMPs. Thus, blocking IL-9 pathways might be an attractive immunotherapeutic target for preventing bone degradation in RA.

Mechanistic insights into the role of B cells in rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease epitomized by severe inflammation that induces tendon, cartilage, and bone damage over time. Although different types of cells undertake pathogenic functions in RA, the B cell's significant involvement has increasingly been known following the development of rheumatoid factor and it has been re-emphasized in recent years. Therefore, the rheumatoid factors and anti-cyclic citrullinated peptide antibodies are well-known indications of infection and clinical manifestations, and that they can precede the development of illness by several years. The emergence of rituximab a B cell reducing chimeric antidote in 1997 and 1998 transformed B-cell-targeted therapy for inflammatory disorder from a research hypothesis to a functional fact. Ever since, several autoantibody-related conditions were addressed, including the more intriguing indications of effectiveness seen in rheumatoid arthritis patients. Numerous types of B-cell-targeted compounds are currently being researched. From the beginning, one of the primary goals of B-cell therapy was to reinstate some kind of immune tolerance. While B cells have long been recognized as essential autoantibody producers, certain antibody-independent functions and usefulness as a key targeted therapy were not recognized until recently. The knowledge of B cells' diverse physical and pathogenic roles in autoimmune diseases is growing. As a result, the number of successful agents targeting the B cell complex is becoming more ubiquitous. Therefore, in this article, we explore fresh perspectives upon the roles of B cells in arthritis treatment, as well as new evidence regarding the effectiveness of B lymphocytes reduction and the therapeutic outcome of biological markers.

Induction of IL-9 in Peripheral Lymphocytes of Rheumatoid Arthritis Patients and Healthy Donors by Th17-Inducing Cytokine Conditions

IL-9-producing Th9 cells display a group of helper T cells with similarities to Th17 and Th2 T cells and have been shown to be involved in synovial inflammation in rheumatoid arthritis (RA) patients. So far, it is unclear which parameters drive Th9 differentiation in lymphocytes derived from RA patients compared to immunologically healthy individuals and whether autocrine mechanisms are able to enhance Th9 polarization. Further, parallel pathways of induction of IL-17-producing cells with Th9 phenotype have to be distinguished from exclusively Th9-inductive mechanisms. Thus, the present study aimed to determine the parameters of Th9 induction by simulation in a standardized inflammatory cytokine milieu.Peripheral naive and non-naive T cells of RA patients and healthy donors (HD) were cultured under Th9 and Th17-driving conditions and phenotypically analyzed by flow cytometry and molecular analysis.Our findings indicate a similar differentiation pathway of Th9 and Th17 cells and similar distributions of IL-9+ T cells in RA and HD regardless of Th9- or Th17-promoting cytokine milieus. Whereas the magnitude and direction of Th9- or Th17-polarization was about the same in RA and HD, IL-17+ CD4+ T cells were significantly stimulated by Th17-inducing conditions in HD. In conclusion, the results indicate that Th9- and Th17-inducing cytokine conditions mimicking autoimmune inflammation in RA may have similar stimulatory effects regarding polarization of peripheral naive and non-naive T cells into Th9 or Th17 cells. The results suggest that the differentiation of Th9 cells may be also induced by Th17-driving conditions.

Inhibiting OX40 Restores Regulatory T-Cell Function and Suppresses Inflammation in Pulmonary Sarcoidosis

BACKGROUND

Pulmonary sarcoidosis (PS) is a noncaseating granulomatous disease of unknown origin. Despite conflicting reports, it is considered that the regulatory T (Treg) cells are functionally impaired in PS, but the underlying mechanisms remain unclear. OX40, a pivotal costimulatory molecule, is essential for T-cell functions and memory development, but its impact on Treg cells is ambiguous.

RESEARCH QUESTION

Does the OX40 pathway influence the suppressive functions of Treg cells in PS?

STUDY DESIGN AND METHODS

Fifty treatment-naïve patients with PS and 30 healthy control participants were recruited for this study. Polychromatic flow cytometry-based immunologic assays were performed to enumerate effector T helper (Th) cells and Treg cells along with their functions. Using real-time polymerase chain reaction analysis, small interfering RNA, and pharmacologic inhibitors, the impact of OX40 on Treg cell function was investigated.

RESULTS

We observed enrichment of Th-9 cells perhaps for the first time along with Th-1, Th-17, and Treg cells in patients' BAL fluid (BALF) compared with peripheral blood. However, Treg cells were observed to be functionally defective at the pathological site. We observed higher expression of OX40 on both T effector (CD4⁺Foxp3^-) and Treg (CD4⁺Foxp3⁺) cells obtained from the BALF of patients with PS. However, OX40 exerted contrasting impact on these T-cell subsets, enhancing effector T-cell functions (interferon γ, tumor necrosis factor α) while inhibiting Treg cell function (IL-10, transforming growth factor β). OX40 silencing or blocking on Treg cells resulted in restoration of their impaired functions.

INTERPRETATION

We propose that inhibiting the OX40 pathway may constitute a therapeutic strategy for controlling inflammatory T cells by restoring Treg cell functions in patients with PS.

Chemokine Receptor 5 Antagonism Causes Reduction in Joint Inflammation in a Collagen-Induced Arthritis Mouse Model

Rheumatoid arthritis (RA) is a chronic inflammatory disease mainly affecting the synovial joints. A highly potent antagonist of C-C chemokine receptor 5 (CCR5), maraviroc (MVC), plays an essential role in treating several infectious diseases but has not yet been evaluated for its potential effects on RA development. This study focused on evaluating the therapeutic potential of MVC on collagen-induced arthritis (CIA) in DBA/1J mice. Following CIA induction, animals were treated intraperitoneally with MVC (50 mg/kg) daily from day 21 until day 35 and evaluated for clinical score and histopathological changes in arthritic inflammation. We further investigated the effect of MVC on Th9 (IL-9, IRF-4, and GATA3) and Th17 (IL-21R, IL-17A, and RORγT) cells, TNF-α, and RANTES in CD8+ T cells in the spleen using flow cytometry. We also assessed the effect of MVC on mRNA and protein levels of IL-9, IL-17A, RORγT, and GATA3 in knee tissues using RT-PCR and western blot analysis. MVC treatment in CIA mice attenuated the clinical and histological severity of inflammatory arthritis, and it substantially decreased IL-9, IRF4, IL-21R, IL-17A, RORγT, TNF-α, and RANTES production but increased GATA3 production in CD8+ T cells. We further observed that MVC treatment decreased IL-9, IL-17A, and RORγt mRNA and protein levels and increased those of GATA3. This study elucidates the capacity of MVC to ameliorate the clinical and histological signs of CIA by reducing pro-inflammatory responses, suggesting that MVC may have novel therapeutic uses in the treatment of RA.

Mesenchymal stem/stromal cells as a valuable source for the treatment of immune-mediated disorders

Over recent years, mesenchymal stem/stromal cells (MSCs) and their potential biomedical applications have received much attention from the global scientific community in an increasing manner. Firstly, MSCs were successfully isolated from human bone marrow (BM), but in the next steps, they were also extracted from other sources, mostly from the umbilical cord (UC) and adipose tissue (AT). The International Society for Cellular Therapy (ISCT) has suggested minimum criteria to identify and characterize MSCs as follows: plastic adherence, surface expression of CD73, D90, CD105 in the lack of expression of CD14, CD34, CD45, and human leucocyte antigen-DR (HLA-DR), and also the capability to differentiate to multiple cell types including adipocyte, chondrocyte, or osteoblast in vitro depends on culture conditions. However, these distinct properties, including self-renewability, multipotency, and easy accessibility are just one side of the coin; another side is their huge secretome which is comprised of hundreds of mediators, cytokines, and signaling molecules and can effectively modulate the inflammatory responses and control the infiltration process that finally leads to a regulated tissue repair/healing or regeneration process. MSC-mediated immunomodulation is a direct result of a harmonic synergy of MSC-released signaling molecules (i.e., mediators, cytokines, and chemokines), the reaction of immune cells and other target cells to those molecules, and also feedback in the MSC-molecule-target cell axis. These features make MSCs a respectable and eligible therapeutic candidate to be evaluated in immune-mediated disorders, such as graft versus host diseases (GVHD), multiple sclerosis (MS), Crohn's disease (CD), and osteoarthritis (OA), and even in immune-dysregulating infectious diseases such as the novel coronavirus disease 2019 (COVID-19). This paper discussed the therapeutic applications of MSC secretome and its biomedical aspects related to immune-mediated conditions. Sources for MSC extraction, their migration and homing properties, therapeutic molecules released by MSCs, and the pathways and molecular mechanisms possibly involved in the exceptional immunoregulatory competence of MSCs were discussed. Besides, the novel discoveries and recent findings on immunomodulatory plasticity of MSCs, clinical applications, and the methods required for their use as an effective therapeutic option in patients with immune-mediated/immune-dysregulating diseases were highlighted.

The attentive focus on T cell-mediated autoimmune pathogenesis of psoriasis, lichen planus and vitiligo

T cell-mediated autoimmune skin diseases develop as a result of the aberrant immune response to the skin cells with T cells playing a central role. These chronic inflammatory skin diseases encompass various types including psoriasis, lichen planus and vitiligo. These diseases show similarities in their immune-pathophysiology. In the last decade, immunomodulating agents have been very successful in the management of these diseases thanks to a better understanding of the pathophysiology. In this review, we will discuss the immunopathogenic mechanisms and highlight the role of T lymphocytes in psoriasis, lichen planus and vitiligo. This study could provide new insights into a better understanding of targeted therapeutic pathways and biological therapies.

Innate Lymphocytes in Inflammatory Arthritis

Inflammatory arthritis (IA) refers to a group of chronic diseases, including rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS), and other spondyloarthritis (SpA). IA is characterized by autoimmune-mediated joint inflammation and is associated with inflammatory cytokine networks. Innate lymphocytes, including innate-like lymphocytes (ILLs) expressing T or B cell receptors and innate lymphoid cells (ILCs), play important roles in the initiation of host immune responses against self-antigens and rapidly produce large amounts of cytokines upon stimulation. TNF (Tumor Necrosis Factor)-α, IFN (Interferon)-γ, Th2-related cytokines (IL-4, IL-9, IL-10, and IL-13), IL-17A, IL-22, and GM-CSF are involved in IA and are secreted by ILLs and ILCs. In this review, we focus on the current knowledge of ILL and ILC phenotypes, cytokine production and functions in IA. A better understanding of the roles of ILLs and ILCs in IA initiation and development will ultimately provide insights into developing effective strategies for the clinical treatment of IA patients.

Calcitriol attenuates TLR2/IL-33 signaling pathway to repress Th9 cell differentiation and potentially limits the pathophysiology of rheumatoid arthritis

There is limited information regarding the TLR2 signaling pathway involved in Th9 cell differentiation. The role of calcitriol in regulating TLR2-mediated Th9 cell development is unknown. Thus, we aimed to unravel the TLR2 signaling pathway in Th9 cells and its regulation by calcitriol. We have used n = 5-6 animals for each murine experiment. Human studies involved five healthy volunteers. Moreover, ten healthy individuals and ten RA patients were included in the study. Murine and human Th9 cells were treated with Calcitriol (100 nM) and Pam₃CSK₄ (2 µg/mL). The number of IL-9+ve cells was determined by flow cytometry. Real-time PCR was used to assess the gene expression. Serum 25(OH)D₃ levels were determined by HPLC. We observed that TLR2 signals via IL-33/ST2 in Th9 cells. Increased TLR2 expression associated with increased IL9 expression and augmented disease severity in RA patients. Calcitriol attenuated TLR2 signaling in murine and human Th9 cells. Low serum vitamin D3 level negatively associated with increased IL-9 and TLR2 expression and disease severity in RA patients. Our data suggest a potential role of calcitriol to ameliorate the disease severity of RA patients.

Attenuation of Murine Collagen-Induced Arthritis by Targeting CD6

OBJECTIVE

CD6 is an important regulator of T cell function that interacts with the ligands CD166 and CD318. To further clarify the significance of CD6 in rheumatoid arthritis (RA), we examined the effects of targeting CD6 in the mouse model of collagen-induced arthritis (CIA), using CD6-knockout (CD6-KO) mice and CD6-humanized mice that express human CD6 in lieu of mouse CD6 on their T cells.

METHODS

We immunized wild-type (WT) and CD6 gene-KO mice with a collagen emulsion to induce CIA. For treatment studies using CD6-humanized mice, mice were immunized similarly and a mouse anti-human CD6 IgG (UMCD6) or control IgG was injected on days 7, 14, and 21. Joint tissues were evaluated for tissue damage, leukocyte infiltration, and local inflammatory cytokine production. Collagen-specific Th1, Th9, and Th17 responses and serum levels of collagen-specific IgG subclasses were also evaluated in WT and CD6-KO mice with CIA.

RESULTS

The absence of CD6 reduced 1) collagen-specific Th9 and Th17, but not Th1 responses, 2) the levels of many proinflammatory joint cytokines, and 3) serum levels of collagen-reactive total IgG and IgG1, but not IgG2a and IgG3. Joint homogenate hemoglobin content was significantly reduced in CD6-KO mice with CIA compared to WT mice with CIA (P < 0.05) (reduced angiogenesis). Moreover, treating CD6-humanized mice with mouse anti-human CD6 monoclonal antibody was similarly effective in reducing joint inflammation in CIA.

CONCLUSION

Taken together, these data suggest that interaction of CD6 with its ligands is important for the perpetuation of CIA and other inflammatory arthritides that are T cell driven.

Differential Secretome Profiling of Human Osteoarthritic Synoviocytes Treated with Biotechnological Unsulfated and Marine Sulfated Chondroitins

Symptomatic slow-acting drugs (SYSADOA) are increasingly used as effective therapies for osteoarthritis, representing an attractive alternative to analgesics or non-steroidal anti-inflammatory drugs to relieve disease symptoms. Pharmaceutical preparations of chondroitin sulfate, derived from animal sources, alone or in combination with glucosamine sulfate, are widely recognized for their beneficial effect on osteoarthritis treatment. A growing interest has also been devoted to understanding the molecular mechanisms modulated by SYSADOA using -omic strategies, most of which rely on chondrocytes as a model system. In this work, by using an integrated strategy based on unbiased proteomics and targeted cytokine profiling by a multiplexed protein array, we identified differences in the secretomes of human osteoarthritic synoviocytes in response to biotechnological unsulfated, and marine sulfated chondroitins treatments. The combined strategy allowed the identification of candidate proteins showing both common and distinct regulation responses to the two treatments of chondroitins. These molecules, mainly belonging to ECM proteins, enzymes, enzymatic inhibitors and cytokines, are potentially correlated to treatment outcomes. Overall, the present results provide an integrated overview of protein changes in human osteoarthritic synoviocytes secretome associated to different chondroitin treatments, thus improving current knowledge of the biochemical effects driven by these drugs potentially involved in pathways associated to osteoarthritis pathogenesis.

CXCR3 antagonist AMG487 inhibits glucocorticoid-induced tumor necrosis factor-receptor-related protein and inflammatory mediators in CD45 expressing cells in collagen-induced arthritis mouse model

Rheumatoid arthritis (RA) is an autoimmune disease classified by uncontrolled joint inflammation leading to the destruction of both cartilage and joints. Despite progress made in RA treatment in the past decade, new drugs with high efficacy and fewer long-term adverse effects are still needed; thus, safe anti-inflammatory therapies for RA are urgently needed. Previous results demonstrated that the CXCR3 antagonist is an extremely attractive therapeutic target for the treatment of several autoimmune diseases, suggesting that it might have an inhibitory effect on RA. In this study, we investigated the effect of AMG487, a selective CXCR3 antagonist, on collagen-induced arthritis (CIA) in mice and evaluated its potential therapeutic mechanism.Following induction of CIA, mice were treated with AMG487 (5 mg/kg, intraperitoneally), to investigate their protective effects against CIA. CD4, CD25, CCR6, IL-9, NF-κB, IL-6, IL-17A, IL-21, STAT6 and Foxp3 expressing GITR⁺ and CD45⁺ cells were measured in the spleen using flow cytometry to assess anti-inflammatory effects of AMG487. The mRNA and protein expression of GITR, CCR6, IL-9, and IL-21 were measured using quantitative real-time PCR and western blot analysis in knee tissue. AMG487 significantly alleviated joint inflammation by decreasing GITR⁺CD25⁺, GITR⁺CD45⁺, GITR⁺IL-9⁺, GITR⁺NF-κB⁺ CD45⁺CD4⁺, CD45⁺CCR6⁺, CD45⁺IL-6⁺ cells, CD45⁺IL-17A⁺, and CD45⁺IL-21⁺, and increasing GITR⁺Foxp3⁺ and GITR⁺STAT6⁺ cells. There was a significant decrease in mRNA and protein expression of GITR, CD4, CCR6, IL-6, IL-9, and IL-21 in knee tissue of CIA mice. This study demonstrates that AMG487 has a potential therapeutic effect on RA and could explore novel anti-inflammatory therapies for its treatment.

Different cytokine patterns induced by Helicobacter pylori and Lactobacillus acidophilus extracts in PBMCs of patients with abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a degenerative inflammatory disease with unknown etiology. AAA is characterized by abdominal aortic dilatation more than 3 cm and is often asymptomatic, but the rupture of aneurysm can lead to death. Age, smoking and male sex are major predisposing factors of AAA. This study compares the effect of Helicobacter (H.) pylori and Lactobacillus (L.) acidophilus on the cytokine profile of PBMCs of 5 men with abdominal aortic aneurysm (AAA) and 5 men with normal/insignificant angiography, CT-Scan and ultrasonography results in the single-culture and in the co-culture with HUVECs. IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-13, IL-17A, IL-17 F, IL-21, IL-22, IFN-γ and TNF-α were measured in culture supernatants using a commercial fluorescent-labeled-bead assay. In general, CagA+ H. pylori-extract induced higher production of IFN-γ, IL-13 and IL-21 by PBMCs. Treatment of patients' PBMCs with CagA⁺H. pylori-extract induced Th2 cytokines while treatment of controls' PBMCs with CagA⁺H. pylori-extract increased Th1 cytokines. In the co-culture, however, patients' PBMCs produced Th1 cytokines irrespective of extract treatment, while controls' PBMCs produced Th2 cytokines and decreased IL-10. CagA+ H. pylori- as well as L. acidophilus-extract induced higher levels of IL-9 by controls' PBMCs in co-culture with HUVECs than patients (P = 0.05 and P = 0.01). The cytokine pattern of PBMCs induced by CagA+ H. pylori- and L. acidophilus-extracts in the co-culture with HUVECs shows differences in AAA patients and in comparison to controls. Decreased secretion of IL-9, IL-21 and IL-22 by PBMCs of patients treated with CagA+ H. pylori extract in co-culture, as opposed to non-AAA controls may indicate the active role ECs play in AAA. Simultaneous production of IL-10 and Th1 cytokines in patients and pronounced Th2 cytokines in controls in response to both bacteria may point to the inherent differences between patients and controls, which need further investigation.

Anti-inflammatory and immune-regulatory cytokines in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by a failure of spontaneous resolution of inflammation. Although the pro-inflammatory cytokines and mediators that trigger RA have been the focus of intense investigations, the regulatory and anti-inflammatory cytokines responsible for the suppression and resolution of disease in a context-dependent manner have been less well characterized. However, knowledge of the pathways that control the suppression and resolution of inflammation in RA is clinically relevant and conceptually important for understanding the pathophysiology of the disease and for the development of treatments that enable long-term remission. Cytokine-mediated processes such as the activation of T helper 2 cells by IL-4 and IL-13, the resolution of inflammation by IL-9, IL-5-induced eosinophil expansion, IL-33-mediated macrophage polarization, the production of IL-10 by regulatory B cells and IL-27-mediated suppression of lymphoid follicle formation are all involved in governing the regulation and resolution of inflammation in RA. By better understanding these immune-regulatory signalling pathways, new therapeutic strategies for RA can be envisioned that aim to balance and resolve, rather than suppress, inflammation.

Interleukin-9 blockage reduces early hepatic granuloma formation and fibrosis during Schistosoma japonicum infection in mice

Hepatic fibrosis induced by schistosomes is regulated by a complex network of cytokines. T helper type 9 (Th9) cells are a new type of effector T helper cells, which mainly secrete the specific cytokine interleukin-9 (IL-9). Interleukin-9 has been shown to contribute to liver fibrosis in patients with chronic hepatitis B and in a mouse model due to carbon tetrachloride. However, the role of IL-9 in schistosomiasis fibrosis remains unknown. In this study, we investigated the roles of IL-9 in schistosomiasis through in vivo and in vitro studies. The in vivo studies found that neutralization of IL-9 reduced liver granulomatous inflammation and collagen deposition around parasite eggs. The in vitro studies found that the treatment of primary hepatic stellate cells with IL-9 induced a significant increase of collagen and α-smooth-muscle actin. Moreover, we also described the dynamics and relevance of IL-9 and IL-4 in mice infected with Schistosoma japonicum. We found that IL-9 might appear more quickly and at higher levels than IL-4. Hence, our findings indicated that IL-9 might play a role in regulating hepatic fibrosis in early-stage schistosomiasis and become a promising approach for regulating hepatic fibrosis caused by S. japonicum.

Osteoimmunology: evolving concepts in bone-immune interactions in health and disease

In terrestrial vertebrates, bone tissue constitutes the 'osteoimmune' system, which functions as a locomotor organ and a mineral reservoir as well as a primary lymphoid organ where haematopoietic stem cells are maintained. Bone and mineral metabolism is maintained by the balanced action of bone cells such as osteoclasts, osteoblasts and osteocytes, yet subverted by aberrant and/or prolonged immune responses under pathological conditions. However, osteoimmune interactions are not restricted to the unidirectional effect of the immune system on bone metabolism. In recent years, we have witnessed the discovery of effects of bone cells on immune regulation, including the function of osteoprogenitor cells in haematopoietic stem cell regulation and osteoblast-mediated suppression of haematopoietic malignancies. Moreover, the dynamic reciprocal interactions between bone and malignancies in remote organs have attracted attention, extending the horizon of osteoimmunology. Here, we discuss emerging concepts in the osteoimmune dialogue in health and disease.

An Update on Interleukin-9: From Its Cellular Source and Signal Transduction to Its Role in Immunopathogenesis

Interleukin-9 (IL-9) is a pleiotropic cytokine and was primarily studied in the context of T helper 2 (TH2)-associated immuno-pathological conditions such as asthma and parasitic infections. There was a paradigm shift in the biology of IL-9 after the recent discovery of TH9 cells, a new subtype of TH cells which secrete IL-9 in copious amounts. This has resulted in renewed interest in this cytokine, which was neglected since discovery because it was considered it to be just another TH2 cytokine. Recent studies have shown that it has multiple cellular sources and is critically involved in the immune-pathogenesis of inflammatory diseases and in guarding immune tolerance. In this review, we will discuss its discovery, gene organization, cellular sources, and signaling pathways. Especially, we will give an update on the recent development regarding its relevance in the immune pathogenesis of human diseases.

The role of BAFF and APRIL in rheumatoid arthritis

Development and activation of B cells quickly became clear after identifying new ligands and receptors in the tumor necrosis factor superfamily. B cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL) are the members of membrane proteins Type 2 family released by proteolytic cleavage of furin to form active, soluble homotrimers. Except for B cells, ligands are expressed by all such immune cells like T cells, dendritic cells, monocytes, and macrophages. BAFF and APRIL have two common receptors, namely TNFR homolog transmembrane activator and Ca2+ modulator and CAML interactor (TACI) and B cell-maturation antigen. BAFF alone can also be coupled with a third receptor called BAFFR (also called BR3 or BLyS Receptor). These receptors are often expressed by immune cells in the B-cell lineage. The binding of BAFF or APRIL to their receptors supports B cells differentiation and proliferation, immunoglobulin production and the upregulation of B cell-effector molecules expression. It is possible that the overexpression of BAFF and APRIL contributes to the pathogenesis of autoimmune diseases. In BAFF transgenic mice, there is a pseudo-autoimmune manifestation, which is associated with an increase in B-lymphocytes, hyperglobulinemia, anti-single stranded DNA, and anti-double-stranded DNA antibodies, and immune complexes in their peripheral blood. Furthermore, overexpressing BAFF augments the number of peripheral B220+ B cells with a normal proliferation rate, high levels of Bcl2, and prolonged survival and hyperactivity. Therefore, in this review article, we studied BAFF and APRIL as important mediators in B-cell and discussed their role in rheumatoid arthritis.

IL-36, IL-37, and IL-38 Cytokines in Skin and Joint Inflammation: A Comprehensive Review of Their Therapeutic Potential

The interleukin (IL)-1 family of cytokines is composed of 11 members, including the most recently discovered IL-36α, β, γ, IL-37, and IL-38. Similar to IL-1, IL-36 cytokines are initiators and amplifiers of inflammation, whereas both IL-37 and IL-38 display anti-inflammatory activities. A few studies have outlined the role played by these cytokines in several inflammatory diseases. For instance, IL-36 agonists seem to be relevant for the pathogenesis of skin psoriasis whereas, despite being expressed within the synovial tissue, their silencing or overexpression do not critically influence the course of arthritis in mice. In this review, we will focus on the state of the art of the molecular features and biological roles of IL-36, IL-37, and IL-38 in representative skin- and joint-related inflammatory diseases, namely psoriasis, rheumatoid arthritis, and psoriatic arthritis. We will then offer an overview of the therapeutic potential of targeting the IL-36 axis in these diseases, either by blocking the proinflammatory agonists or enhancing the physiologic inhibitory feedback on the inflammation mediated by the antagonists IL-37 and IL-38.

Neutrophil Function in an Inflammatory Milieu of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease characterized by the presence of autoantibodies against citrullinated protein antigens and proinflammatory cytokines which cause chronic synovitis, bone erosion, and eventual deformity; however, the precise etiology of RA is unclear. In the early stage of RA, neutrophils migrate into the articular cavity, become activated, and exert their function in an inflammatory process, suggesting an essential role of neutrophils in the initial events contributing to the pathogenesis of RA. Solid evidence exists that supports the contribution of neutrophil extracellular traps (NETs) to the production of autoantibodies against citrullinated proteins which can trigger the immune reaction in RA. Concurrently, proinflammatory cytokines regulate the neutrophil migration, apoptosis, and NET formation. As a result, the inflammatory neutrophils produce more cytokines and influence other immune cells thereby perpetuating the inflammatory condition in RA. In this review, we summarize the advances made in improving our understanding of neutrophil migration, apoptosis, and NET formation in the presence of an RA inflammatory milieu. We will also discuss the most recent strategies in modulating the inflammatory microenvironment that have an impact on neutrophil function which may provide alternative novel therapies for RA.

Pathogenic Role of Immune Cells in Rheumatoid Arthritis: Implications in Clinical Treatment and Biomarker Development

Rheumatoid arthritis (RA) is a chronic, autoimmune, systemic, inflammatory disorder that affects synovial joints, both small and large joints, in a symmetric pattern. This disorder usually does not directly cause death but significantly reduces the quality of life and life expectancy of patients if left untreated. There is no cure for RA but, patients are usually on long-term disease modifying anti-rheumatic drugs (DMARDs) to suppress the joint inflammation, to minimize joint damage, to preserve joint function, and to keep the disease in remission. RA is strongly associated with various immune cells and each of the cell type contributes differently to the disease pathogenesis. Several types of immunomodulatory molecules mainly cytokines secreted from immune cells mediate pathogenesis of RA, hence complicating the disease treatment and management. There are various treatments for RA depending on the severity of the disease and more importantly, the patient’s response towards the given drugs. Early diagnosis of RA and treatment with (DMARDs) are known to significantly improve the treatment outcome of patients. Sensitive biomarkers are crucial in early detection of disease as well as to monitor the disease activity and progress. This review aims to discuss the pathogenic role of various immune cells and immunological molecules in RA. This review also highlights the importance of understanding the immune cells in treating RA and in exploring novel biomarkers.