Neutrophils produce interleukin-17B in rheumatoid synovial tissue

IL-17 family cytokines in inflammatory or autoimmune skin diseases

As potent pro-inflammatory mediators, IL-17 family cytokines play crucial roles in the pathogenesis of various inflammatory and autoimmune skin disorders. Although substantial progress has been achieved in understanding the pivotal role of IL-17A signaling in psoriasis, leading to the development of highly effective biologics, the functions of other IL-17 family members in inflammatory or autoimmune skin diseases remain less explored. In this review, we provide a comprehensive overview of IL-17 family cytokines and their receptors, with a particular focus on the recent advancements in identifying cellular sources, receptors and signaling pathways regulated by these cytokines. At the end, we discuss how the aberrant functions of IL-17 family cytokines contribute to the pathogenesis of diverse inflammatory or autoimmune skin diseases.

Triptolide regulates neutrophil function through the Hippo signaling pathway to alleviate rheumatoid arthritis disease progression

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by inflammatory changes in the joints, the etiology of which is unclear. It is now well established that regulated cell death (RCD) and migration of neutrophils play an important role in the pathogenesis of RA. Tripterygium wilfordii Hook.f (TwHF) is a total saponin extracted from the root of Tripterygium wilfordii Hook.f, a plant of the family Wesleyanaceae, which has strong anti-inflammatory and immunomodulatory effects and has been used as a basic drug in the clinical treatment of RA. Despite the good efficacy of TwHF treatment, the mechanism of action of TwHF remains unclear. Several studies have demonstrated that the drug tripterygium glycosides, in which TwHF is the main ingredient, has achieved excellent efficacy in the clinical treatment of RA. Investigations have also found that TwHF can affect cellular RCD, cell migration, cell proliferation, and the apoptosis-related Hippo signaling pathway. In this study, we first analyzed the RCD and migration differences of neutrophils in patients with RA through network pharmacology and transcriptome analysis. Subsequently, we used electron microscopy, immunofluorescence, and other methods to identify the RCD phenotype of neutrophils. In collagen-induced arthritis (CIA) model, we demonstrated that Triptolide (the main active ingredient in TwHF) could alleviate the progression of arthritis by reducing the bone destruction and the infiltration of neutrophils. Furthermore, in vitro experiments showed that Triptolide induced neutrophil apoptosis, inhibited the formation of neutrophil extracellular traps (NETs), and impeded the neutrophil migration process in a Hippo pathway-dependent manner. Taken together, these findings indicate that Triptolide has potential for treating RA and provide theoretical support for the clinical application of TwHF, as a traditional Chinese medicine, in RA.

Comprehensive analysis of serum exosome-derived lncRNAs and mRNAs from patients with rheumatoid arthritis

BACKGROUND

Serum exosomes play important roles in intercellular communication and are promising biomarkers of several autoimmune diseases. However, the biological functions and potential clinical importance of long non-coding RNAs (lncRNAs) and mRNAs from serum exosomes in rheumatoid arthritis (RA) have not yet been studied.

METHODS

Serum exosomal lncRNAs and mRNAs were isolated from patients with RA and osteoarthritis (OA) and healthy controls. The differentially expressed lncRNAs (DE-lncRNAs) and mRNA profiles in the serum exosomes of patients with RA were analysed using high-throughput sequencing, and their functions were predicted using Gene Ontologyenrichment, Kyoto Encyclopedia of Genes and Genomes pathway, and gene set enrichment analysis. We constructed a DE-lncRNA-mRNA network and a protein-protein interaction network of differentially expressed mRNAs (DE-mRNAs) in RA using the Cytoscape software. The expression of several candidate a DE-lncRNAs and DE-mRNAs in the serum of patients with RA, patients with OA, and healthy controls was confirmed by qRT-PCR. We assessed the diagnostic ability of DE-lncRNAs and DE-mRNAs in patients with RA using receiver operating characteristic analysis. Furthermore, we analysed the characteristics of immune cell infiltration in RA by digital cytometry using the CIBERSORT algorithm and determined the correlation between immune cells and several DE-lncRNAs or DE-mRNAs in RA.

RESULTS

The profiles of serum exosomal lncRNAs and mRNAs in patients with RA were different from those in healthy controls and patients with OA. The functions of both DE-lncRNAs and DE-mRNAs in RA are associated with the immune response and cellular metabolic processes. The RT-PCR results show that NONHSAT193357.1, CCL5, and MPIG6B were downregulated in patients with RA. The combination of three DE-mRNAs, CCL5, MPIG6B, and PFKP, had an area under the curve of 0.845 for differentiating RA from OA. Digital cytometry using the CIBERSORT algorithm showed that the neutrophil counts were higher in patients with RA than those in healthy controls and patients with OA.

CONCLUSIONS

These findings help to elucidate the role of serum exosomal lncRNAs and mRNAs in the specific mechanisms underlying RA.

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.

Evolutional perspective and functional characteristics of interleukin-17 in teleosts

Interleukin (IL)-17 is a proinflammatory cytokine and plays essential roles in adaptive and innate immune responses against bacterial and fungal infections. Especially in mammalian mucosal tissues, it is well known that innate immune responses via IL-17A and IL-17F, such as the production of antimicrobial peptides, are very important for microbiota control. In contrast, interesting insights into the functions of IL-17 have recently been reported in several teleost species, although little research has been conducted on teleost IL-17. In the present review, we focused on current insights on teleost IL-17 and speculated on the different or consensus parts of teleost IL-17 signaling compared to that of mammals. This review focuses on the role of teleost IL-17 in intestinal immunity. We expect that this review will encourage a further understanding of the roles and importance of IL-17 signaling in teleosts.

Bovine skin fibroblasts mediated immune responses to defend against bovine Acinetobacter baumannii infection

Acinetobacter baumannii (A. baumannii) is an opportunistic pathogen which can cause pneumonia, sepsis and infections of skin and soft tissue. The host mostly relies on innate immune responses to defend against the infection of A. baumannii. Currently, it has been confirmed that fibroblasts involved in innate immune responses. Therefore, to explore how bovine skin fibroblasts mediated immune responses to defend against A. baumannii infection, we analyzed the differential transcripts data of bovine skin fibroblasts infected with bovine A. baumannii by RNA-sequencing (RNA-seq). We found that there were 3014 differentially expressed genes (DEGs) at 14h with bovine A. baumannii infection, including 1940 up-regulated genes and 1074 down-regulated genes. Gene Ontology (GO) enrichment showed that ubiquitin protein ligase binding, IL-6 receptor complex, ERK1 and ERK2 cascade terms were mainly enriched. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment showed that innate immune pathways were significantly enriched, such as TNF, IL-17, NLR, MAPK, NF-κB, endocytosis, apoptosis and HIF-1 signaling pathways. Furthermore, Gene Set Enrichment Analysis (GSEA) revealed that GO terms such as chemokine receptor binding and Th17 cell differentiation and KEGG pathways such as TLR and cytokine-cytokine receptor interaction pathways were up-regulated. In addition, CASP3 and JUN were the core functional genes of apoptosis, while IL-6, ERBB2, EGFR, CHUK and MAPK8 were the core functional genes of immunity by Protein-Protein Interaction (PPI) analysis. Our study provided an in-depth understanding of the molecular mechanisms of fibroblasts against A. baumannii infection. It also lays the foundation for the development of new therapeutic targets for the diseases caused by A. baumannii infection and formulates effective therapeutic strategies for the prevention and control of the diseases caused by A. baumannii.

Interleukin-17 Family Cytokines in Metabolic Disorders and Cancer

Interleukin-17 (IL-17) family cytokines are potent drivers of inflammatory responses. Although IL-17 was originally identified as a cytokine that induces protective effects against bacterial and fungal infections, IL-17 can also promote chronic inflammation in a number of autoimmune diseases. Research in the last decade has also elucidated critical roles of IL-17 during cancer development and treatment. Intriguingly, IL-17 seems to play a role in the risk of cancers that are associated with metabolic disorders. In this review, we summarize our current knowledge on the biochemical basis of IL-17 signaling, IL-17′s involvement in cancers and metabolic disorders, and postulate how IL-17 family cytokines may serve as a bridge between these two types of diseases.

Targeting interleukin-17 enhances tumor response to immune checkpoint inhibitors in colorectal cancer

Although immune checkpoint inhibitors (ICIs) have gained much attention in managing cancer, only a minority of patients, especially those with tumors that have been classified as immunologically "cold" such as microsatellite stable (MSS) colorectal cancers (CRC), experience clinical benefit from ICIs. Surprisingly, interleukin-17 (IL-17) and its primary source Th17 are enriched in CRC and inversely associated with patient outcome. Our previous study revealed that IL-17A could upregulate programmed death-ligand 1 (PD-L1) expression and impede the efficacy of immunotherapy. IL-17, therefore, can be a possible target to sensitize tumor cells to ICIs. The detailed clinical results from our trial, which is the first to show the benefits of the combination of anti-PD-1 with anti-IL-17 therapy for MSS CRC, have also been presented. In this review, we highlight the role of IL-17 in ICIs resistance and summarize the current clinical evidence for the use of combination therapy. Directions for future strategies to warm up immunologically "cold" MSS CRCs have also been proposed.

Role of IL-17 family cytokines in the progression of IPF from inflammation to fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal chronic interstitial lung disease with no established treatment and is characterized by progressive scarring of the lung tissue and an irreversible decline in lung function. Chronic inflammation has been demonstrated to be the pathological basis of fibrosis. Emerging studies have revealed that most interleukin-17 (IL-17) isoforms are essential for the mediation of acute and chronic inflammation via innate and adaptive immunity. Overexpression or aberrant expression of IL-17 cytokines contributes to various pathological outcomes, including the initiation and exacerbation of IPF. Here, we aim to provide an overview of IL-17 family members in the pathogenesis of IPF.

The emerging role of neutrophils in autoimmune-associated disorders: effector, predictor, and therapeutic targets

Neutrophils are essential components of the immune system and have vital roles in the pathogenesis of autoimmune disorders. As effector cells, neutrophils promote autoimmune disease by releasing cytokines and chemokines cascades that accompany inflammation, neutrophil extracellular traps (NETs) regulating immune responses through cell-cell interactions. More recent evidence has extended functions of neutrophils. Accumulating evidence implicated neutrophils contribute to tissue damage during a broad range of disorders, involving rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), primary sjögren's syndrome (pSS), multiple sclerosis (MS), crohn's disease (CD), and gout. A variety of studies have reported on the functional role of neutrophils as therapeutic targets in autoimmune diseases. However, challenges and controversies in the field remain. Enhancing our understanding of neutrophils' role in autoimmune disorders may further advance the development of new therapeutic approaches.

From Messengers to Receptors in Psoriasis: The Role of IL-17RA in Disease and Treatment

The paradigm of psoriasis as a Th17-driven disease has evolved in the last years towards a much deeper knowledge of the complex pathways, mechanisms, cells, and messengers involved, highlighting the crucial role played by the IL-17 family of cytokines. All IL-17 isoforms signal through IL-17R. Five subunits of IL-17R have been described to date, which couple to form a homo- or hetero-receptor complex. Characteristically, IL-17RA is a common subunit in all hetero-receptors. IL-17RA has unique structural—containing a SEFIR/TILL domain—and functional—requiring ACT-1 for signaling—properties, enabling Th17 cells to act as a bridge between innate and adaptive immune cells. In psoriasis, IL-17RA plays a key role in pathogenesis based on: (a) IL-17A, IL-17F, and other IL-17 isoforms are involved in disease development; and (b) IL-17RA is essential for signaling of all IL-17 cytokines but IL-17D, whose receptor has not been identified to date. This article reviews current evidence on the biology and role of the IL-17 family of cytokines and receptors, with focus on IL-17RA, in psoriasis and some related comorbidities, and puts them in context with current and upcoming treatments.

Roles of IL-25 in Type 2 Inflammation and Autoimmune Pathogenesis

Interleukin-17E (IL-25) is a member of the IL-17 cytokine family that includes IL-17A to IL-17F. IL-17 family cytokines play a key role in host defense responses and inflammatory diseases. Compared with other IL-17 cytokine family members, IL-25 has relatively low sequence similarity to IL-17A and exhibits a distinct function from other IL-17 cytokines. IL-25 binds to its receptor composed of IL-17 receptor A (IL-17RA) and IL-17 receptor B (IL-17RB) for signal transduction. IL-25 has been implicated as a type 2 cytokine and can induce the production of IL-4, IL-5 and IL-13, which in turn inhibits the differentiation of T helper (Th) 17. In addition to its anti-inflammatory properties, IL-25 also exhibits a pro-inflammatory effect in the pathogenesis of Th17-dominated diseases. Here, we review recent advances in the roles of IL-25 in the pathogenesis of inflammation and autoimmune diseases.

Identification of Novel Serological Autoantibodies in Takayasu Arteritis Patients Using HuProt Arrays

To identify novel autoantibodies of Takayasu arteritis (TAK) using HuProt array-based approach, a two-phase approach was adopted. In Phase I, serum samples collected from 40 TAK patients, 15 autoimmune disease patients, and 20 healthy subjects were screened to identify TAK-specific autoantibodies using human protein (HuProt) arrays. In phase II, the identified candidate autoantibodies were validated with TAK-focused arrays using an additional cohort comprised of 109 TAK patients, 110 autoimmune disease patients, and 96 healthy subjects. Subsequently, the TAK-specific autoantibodies validated in phase II were further confirmed using western blot analysis. We identified and validated eight autoantibodies as potential TAK-specific diagnostic biomarkers, including anti-SPATA7, -QDPR, -SLC25A2, -PRH2, -DIXDC1, -IL17RB, -ZFAND4, and -NOLC1 antibodies, with AUC of 0.803, 0.801, 0.780, 0.696, 0.695, 0.678, 0.635, and 0.613, respectively. SPATA7 could distinguish TAK from healthy and disease controls with 73.4% sensitivity at 85.4% specificity, while QDPR showed 71.6% sensitivity at 86.4% specificity. SLC25A22 showed the highest sensitivity of 80.7%, but at lower specificity of 67.0%. In addition, PRH2, IL17RB, and NOLC1 showed good specificities of 88.3%, 85.9%, and 86.9%, respectively, but at lower sensitivities (<50%). Finally, DIXDC1 and ZFAND4 showed moderate performance as compared with the other autoantibodies. Using a decision tree model, we could reach a specificity of 94.2% with AUC of 0.843, a significantly improved performance as compared with that by each individual biomarker. The performances of three autoantibodies, namely anti-SPATA7, -QDPR, and -PRH2, were successfully confirmed with western blot analysis. Using this two-phase strategy, we identified and validated eight novel autoantibodies as TAK-specific biomarker candidates, three of which could be readily adopted in a clinical setting.

Much More Than IL-17A: Cytokines of the IL-17 Family Between Microbiota and Cancer

The interleukin-(IL-)17 family of cytokines is composed of six members named IL-17A, IL-17B, IL-17C, IL-17D, IL-17E, and IL-17F. IL-17A is the prototype of this family, and it was the first to be discovered and targeted in the clinic. IL-17A is essential for modulating the interplay between commensal microbes and epithelial cells at our borders (i.e., skin and mucosae), and yet, for protecting us from microbial invaders, thus preserving mucosal and skin integrity. Interactions between the microbiota and cells producing IL-17A have also been implicated in the pathogenesis of immune mediated inflammatory diseases and cancer. While interactions between microbiota and IL-17B-to-F have only partially been investigated, they are by no means less relevant. The cellular source of IL-17B-to-F, their main targets, and their function in homeostasis and disease distinguish IL-17B-to-F from IL-17A. Here, we intentionally overlook IL-17A, and we focus instead on the role of the other cytokines of the IL-17 family in the interplay between microbiota and epithelial cells that may contribute to cancer pathogenesis and immune surveillance. We also underscore differences and similarities between IL-17A and IL-17B-to-F in the microbiota-immunity-cancer axis, and we highlight therapeutic strategies that directly or indirectly target IL-17 cytokines in diseases.

Interleukin-17 in rheumatoid arthritis: Trials and tribulations

Interleukin-17A (IL-17A) is a pro-inflammatory cytokine with well-characterized biological effects on stromal cell activation, angiogenesis, and osteoclastogenesis. The presence of this cytokine in the inflamed joints of patients with rheumatoid arthritis (RA), together with compelling data from in vitro and experimental arthritis models demonstrating its pro-inflammatory effects, made this cytokine a strong candidate for therapeutic targeting. Clinical trials, however, have shown relatively modest success in RA as compared with other indications. Guided by recent insights in IL-17 biology, this review aims to explore possible reasons for the limited clinical efficacy of IL-17A blockade in RA, and what we can learn from these results going forward.

Cytokines of the IL-17 family in psoriasis

Various immune cells and their messenger substances influence the development of psoriasis. Cytokines of the IL-17 family are of particular importance. In addition to IL-17A, which plays a central role in the pathogenesis of psoriasis, other subtypes of the IL-17 family also have a proinflammatory effect. This review provides an up-to-date overview of the immunopathogenesis of psoriasis with regard to the six IL-17 subtypes, in particular their physiological and pathogenic properties, as well as their significance for psoriasis therapy.

The Emerging Role of the IL-17B/IL-17RB Pathway in Cancer

Among inflammatory mediators, a growing body of evidence emphasizes the contribution of the interleukin 17 (IL-17) cytokine family in malignant diseases. Besides IL-17A, the prototypic member of the IL-17 family, several experimental findings strongly support the role of the IL-17B/IL-17 receptor B (IL-17RB) pathway in tumorigenesis and resistance to anticancer therapies. In mouse models, IL-17B signaling through IL-17RB directly promotes cancer cell survival, proliferation, and migration, and induces resistance to conventional chemotherapeutic agents. Importantly, recent work by our and other laboratories showed that IL-17B signaling dramatically alters the tumor microenvironment by promoting chemokine and cytokine secretion which foster tumor progression. Moreover, the finding that elevated IL-17B is associated with poor prognosis in patients with pancreatic, gastric, lung, and breast cancer strengthens the results obtained in pre-clinical studies and highlights its clinical relevance. Here, we review the current understanding on the IL-17B/IL-17RB expression patterns and biological activities in cancer and highlight issues that remain to be addressed to better characterize IL-17B and its receptor as potential targets for enhancing the effectiveness of the existing cancer therapies.

Cutting Edge: IL-17B Uses IL-17RA and IL-17RB to Induce Type 2 Inflammation from Human Lymphocytes

IL-17 family cytokines are critical to host defense responses at cutaneous and mucosal surfaces. Whereas IL-17A, IL-17F, and IL-17C induce overlapping inflammatory cascades to promote neutrophil-mediated immunity, IL-17E/IL-25 drives type 2 immune pathways and eosinophil activity. Genetic and pharmacological studies reveal the significant contribution these cytokines play in antimicrobial and autoimmune mechanisms. However, little is known about the related family member, IL-17B, with contrasting reports of both pro- and anti-inflammatory function in rodents. We demonstrate that in the human immune system, IL-17B is functionally similar to IL-25 and elicits type 2 cytokine secretion from innate type 2 lymphocytes, NKT, and CD4⁺ CRTH2⁺ Th2 cells. Like IL-25, this activity is dependent on the IL-17RA and IL-17RB receptor subunits. Furthermore, IL-17B can augment IL-33-driven type 2 responses. These data position IL-17B as a novel component in the regulation of human type 2 immunity.

Relationship of hematologic markers with IL-17 and IL-1 beta in patients with rheumatoid arthritis

OBJECTIVES

In this study, we aimed to investigate the relationship of NLR (Neutrophil lymphocyte ratio), MPV (mean platelet volume), PDW (distribution width) rates in rheumatoid arthritis (RA) patients with IL-17 and IL-1 beta which are within the cytokines playing an important role in etiopathogenesis and activity of the disease.

PATIENTS AND METHODS

Fifty-seven RA patients diagnosed according to RA classification criteria of ACR/EULAR 2010 and 37 controls were included into the study. WBC (white blood cell), NEU (neutrophil), PLT (platelet), LYM (lymphocyte) values in complete blood count received from routine blood examination of patients were recorded, and NLR, PLR (platelet lymphocyte ratio) rates were recorded. IL-17 and IL-1 beta were studies in serum samples. Disease activity of RA patients was evaluated with Disease Activity Score (DAS28). Age, gender, disease age, BMI (body mass index), medications used, co-morbid diseases, smoking of the patients were recorded.

RESULTS

Fifty-seven RA patients (46 (80.7%) females, 11 (19.3%) males), and 34 patients (24 (70.6% females and 10 (29.4) males) as a control group were involved. Demographic characteristics were similar between two groups, and statistically significant difference was not detected between patient and control groups in terms of gender, age, and BMI (p> 0.05). We found higher NLR, MPV, PDW, IL-17 values in RA patients compared to control group (p< 0.05). There was a positive correlation of NLR with DAS28, CRP. While erythrocyte sedimentation rate (ESR) had negative correlation with MPV and PDW, it had positive correlation with PLT. We found positive correlation of C-reactive protein (CRP) with NLR and PLT. We could not find correlation of IL-1 beta and IL-17 with hematologic markers.

CONCLUSION

In this study, we investigated the relationship of IL-17 and IL-1 beta which play an important role in pathogenesis of RA patients with the parameters analyzed in routine complete blood count, providing information about disease activity such as DAS 28, CRP, and ESR. We illuminated on an issue which has not discussed before by looking from a different angle. More extensive, follow-up studies are needed to emphasize the importance of these parameters and to reveal the relationship between cytokines during the follow-up of the disease activity.

Cytokine production by human neutrophils: Revisiting the "dark side of the moon"

Polymorphonuclear neutrophils are the most numerous leucocytes present in human blood, and function as crucial players in innate immune responses. Neutrophils are indispensable for the defence towards microbes, as they effectively counter them by releasing toxic enzymes, by synthetizing reactive oxygen species and by producing inflammatory mediators. Interestingly, recent findings have highlighted an important role of neutrophils also as promoters of the resolution of inflammation process, indicating that their biological functions go well beyond simple pathogen killing. Consistently, data from the last decades have highlighted that neutrophils may even contribute to the development of adaptive immunity by performing previously unanticipated functions, including the capacity to extend their survival, directly interact with other leucocytes or cell types, and produce and release a variety of cytokines. In this article, we will summarize the main features of, as well as emphasize some important concepts on, the production of cytokines by human neutrophils.

The IL-17 Family of Cytokines in Psoriasis: IL-17A and Beyond

Psoriasis is a frequent chronic inflammatory skin disease, nowadays considered a major global health problem. Several new drugs, targeting the IL-23/IL-17A pathway, have been recently licensed or are in clinical development. These therapies represent a major improvement of the way in which psoriasis is managed, since they show an unprecedented efficacy on skin symptoms of psoriasis. This has been made possible, thanks to an increasingly more accurate pathogenic view of psoriasis. Today, the belief that Th17 cells mediate psoriasis is moving to the concept of psoriasis as an IL-17A-driven disease. New questions arise at the horizon, given that IL-17A is part of a newly described family of cytokines, which has five distinct homologous: IL-17B, IL-17C, IL-17D, IL-17E, also known as IL-25 and IL-17F. IL-17 family cytokines elicit similar effects in target cells, but simultaneously trigger different and sometimes opposite functions in a tissue-specific manner. This is complicated by the fact that IL-17 cytokines show a high capacity of synergisms with other inflammatory stimuli. In this review, we will summarize the current knowledge around the cytokines belonging to the IL-17 family in relation to skin inflammation in general and psoriasis in particular, and discuss possible clinical implications. A comprehensive understanding of the different roles played by the IL-17 cytokines is crucial to appreciate current and developing therapies and to allow an effective pathogenesis- and mechanisms-driven drug design.

TGF-β1 secreted by Tregs in lymph nodes promotes breast cancer malignancy via up-regulation of IL-17RB

Lymph node (LN) metastasis is commonly associated with systemic distant organ metastasis in human breast cancer and is an important prognostic predictor for survival of breast cancer patients. However, whether tumor‐draining LNs (TDLNs) play a significant role in modulating the malignancy of cancer cells for distant metastasis remains controversial. Using a syngeneic mouse mammary tumor model, we found that breast tumor cells derived from TDLN have higher malignancy and removal of TDLNs significantly reduced distant metastasis. Up‐regulation of oncogenic Il‐17rb in cancer cells derived from TDLNs contributes to their malignancy. TGF‐β1 secreted from regulatory T cells (Tregs) in the TDLNs mediated the up‐regulation of Il‐17rb through downstream Smad2/3/4 signaling. These phenotypes can be abolished by TGF‐β1 neutralization or depletion of Tregs. Consistently, clinical data showed that the up‐regulation of IL‐17RB in cancer cells from LN metastases correlated with the increased prevalence of Tregs as well as the aggressive growth of tumors in mouse xenograft assay. Together, these results indicate that Tregs in TDLNs play an important role in modulating the malignancy of breast cancer cells for distant metastasis. Blocking IL‐17RB expression could therefore be a potential approach to curb the process.

In vivo exposure to hydroquinone during the early phase of collagen-induced arthritis aggravates the disease

Robust correlation between the severity of rheumatoid arthritis (RA) and cigarette smoking has been clinically demonstrated. Nevertheless, cigarette compounds responsible for this toxic effect and their mechanisms have not been described. Considering that hydroquinone (HQ) is an abundant, pro-oxidative compound of the matter particle phase of cigarette smoke, we investigated whether HQ exposure during the initial phase of collagen-induced arthritis (CIA) could aggravate the disease. For this purpose, male Wistar rats were exposed to aerosolized HQ (25 ppm), saline or 5% ethanol solution (HQ vehicle) for 1 h per day during 14 days. CIA was induced through s.c. injection of bovine collagen Type II (0.4 mg/100 μL) at days seven and 14 of exposure. Clinical signs of disease and the cell profile and chemical mediators in the synovial fluid and membrane were analysed at day 35 after the beginning of exposure. HQ exposure aggravated CIA-related paw edema and increased the cell infiltrate and interleukin-6 (IL-6) levels in the synovial fluid, promoted intense tissue collagen deposition and enhanced synoviocyte proliferation and higher frequency of aryl hydrocarbon receptor (AhR⁺) and interleukin (IL-17⁺) neutrophils in the synovial membrane. in vitro data also highlighted that neutrophils expressed increased levels of AhR, IL-17 and reactive oxygen species (ROS) generation. However, only AhR expression and ROS generation were blocked by in vitro treatment with AhR antagonist. Therefore, we conclude that in vivo HQ exposure at the early phase of AR onset worsens RA, leading to high frequency of AhR/IL-17⁺ neutrophils into the joint.

A Reappraisal on the Potential Ability of Human Neutrophils to Express and Produce IL-17 Family Members In Vitro: Failure to Reproducibly Detect It

Neutrophils are known to perform a series of effector functions that are crucial for the innate and adaptive responses, including the synthesis and secretion of a variety of cytokines. In light of the controversial data in the literature, the main objective of this study was to more in-depth reevaluate the capacity of human neutrophils to express and produce cytokines of the IL-17 family in vitro. By reverse transcription quantitative real-time PCR, protein measurement via commercial ELISA, immunohistochemistry (IHC) and immunofluorescence (IF), flow cytometry, immunoblotting, chromatin immunoprecipitation (ChIP), and ChIP-seq experiments, we found that highly pure (>99.7%) populations of human neutrophils do not express/produce IL-17A, IL-17F, IL-17AF, or IL-17B mRNA/protein upon incubation with a variety of agonists. Similar findings were observed by analyzing neutrophils isolated from active psoriatic patients. In contrast with published studies, IL-17A and IL-17F mRNA expression/production was not even found when neutrophils were incubated with extremely high concentrations of IL-6 plus IL-23, regardless of their combination with inactivated hyphae or conidia from Aspergillus fumigatus. Consistently, no deposition of histone marks for active (H3K27Ac) and poised (H3K4me1) genomic regulatory elements was detected at the IL-17A and IL-17F locus of resting and IL-6 plus IL-23-stimulated neutrophils, indicating a closed chromatin conformation. Concurrent experiments revealed that some commercial anti-IL-17A and anti-IL-17B antibodies (Abs), although staining neutrophils either spotted on cytospin slides or present in inflamed tissue samples by IHC/IF, do not recognize intracellular protein having the molecular weight corresponding to IL-17A or IL-17B, respectively, in immunoblotting experiments of whole neutrophil lysates. By contrast, the same Abs were found to more specifically recognize other intracellular proteins of neutrophils, suggesting that their ability to positively stain neutrophils in cytospin preparations and, eventually, tissue samples derives from IL-17A- or IL-17B-independent detections. In sum, our data confirm and extend, also at epigenetic level, previous findings on the inability of highly purified populations of human neutrophils to express/produce IL-17A, IL-17B, and IL-17F mRNAs/proteins in vitro, at least under the experimental conditions herein tested. Data also provide a number of justifications explaining, in part, why it is possible to false positively detect IL-17A⁺-neutrophils.

Interleukin 17 Family Cytokines: Signaling Mechanisms, Biological Activities, and Therapeutic Implications

The cytokines of the interleukin 17 (IL-17) family play a central role in the control of infections, especially extracellular fungi. Conversely, if unrestrained, these inflammatory cytokines contribute to the pathology of numerous autoimmune and chronic inflammatory conditions. Recent advances have led to the approval of IL-17A-blocking biologics for the treatment of moderate to severe plaque psoriasis, but much remains to be understood about the biological functions, regulation, and signaling pathways downstream of these factors. In this review, we outline the current knowledge of signal transduction and known physiological activities of IL-17 family cytokines. We will highlight in particular the current understanding of these cytokines in the context of skin manifestations of disease.

The Relationship Between Serum Pentraxine 3 Levels and Hematological Markers in Patients With Rheumatoid Arthritis

Objectives

This study aims to investigate the association of pentraxin 3 (PTX3) with neutrophil/lymphocyte ratio (NLR) rather than the disease activity score 28 using C-reactive protein in rheumatoid arthritis (RA).

Patients and methods

The study included 59 RA patients (11 males, 48 females; mean age 53.79±13.55 years; range 40 to 66 years) and 20 healthy controls (5 males, 15 females; mean age 50.41±6.11 years; range 43 to 56 years). Complete blood count tests were recorded and NLR and platelet/ lymphocyte ratio were calculated. PTX3 and interleukin-6 levels were examined in serum samples. Disease activity of RA patients was assessed by disease activity score 28.

Results

Demographic characteristics were similar between the two groups, with no statistically significant difference in terms of sex, age, and body mass index (p>0.05). NLR, PTX3 and interleukin-6 levels were higher in patients with RA than the control group (p<0.05). While erythrocyte sedimentation rate had a positive correlation with mean platelet volume, we found no correlation between NLR and other parameters of disease activity, PTX3, and interleukin-6.

Conclusion

We found no correlation between PTX3 and disease activity score 28 or NLR, although PTX3 levels were higher in RA patients than the controls. As a result, we were unable to establish a relationship between PTX3 and disease activity, directly or indirectly. To our knowledge, our study was the first to investigate the relationship between PTX3 and NLR.

A review article on brodalumab in the treatment of moderate-to-severe plaque psoriasis

Psoriasis is a chronic immune-mediated skin disorder affecting approximately 2-3% of the worldwide population. Recent advances in our understanding of the immunopathogenesis of psoriasis have resulted in novel therapeutic agents. IL-17, a pro-inflammatory cytokine, plays a pivotal role in psoriasis. Therapeutic agents targeting this cytokine have shown clinical effectiveness in the treatment of moderate-to-severe plaque psoriasis. Brodalumab, a human antibody against IL-17 receptor A, has been approved by the US FDA in February 2017, by the Japanese Pharmaceuticals and Medical Devices Agency in July 2016 and by the EMA in July 2017 for the treatment of moderate-to-severe psoriasis. This article reviews the published data relating to brodalumab for the treatment of moderate-to-severe plaque psoriasis.

Molecular cloning of chicken interleukin-17B, which induces proinflammatory cytokines through activation of the NF-κB signaling pathway

Interleukin (IL)-17B is a little known member of the IL-17 cytokine family, which plays an important role in immunity by regulating the expression of proinflammatory cytokines. In this study, we determined the coding sequence and biological functions of a novel chicken IL-17B (chIL-17B). The full-length chIL-17B coding sequence includes 567 nucleotides encoding 188 amino acids, which was identified in small intestinal epithelial cells. The chIL-17B protein shares 96.48% amino acid sequence identity with turkey, 92.57% with duck, and 44.92-64.06% with mammalian IL-17B proteins. ChIL-17B shares three exons and two introns with mammals, turkey, and duck. Moreover, IL-17B mRNA was more highly expressed than IL-17A mRNA in several organs of chickens infected with Salmonella and was upregulated in chicken cell lines following LPS stimulation. In addition, in chicken cell lines, chIL-17B induced the mRNA expression of several proinflammatory cytokines, including IL-1β, IL-6, LITAF, and INF-γ, but not IL-17A, and activated MyD88, TAK1, NF-κB1, and SOCS1, which are associated with the NF-κB signaling pathway. Taken together, chicken interleukin-17B plays a critical role in host defense against the bacterial pathogens, and regulates proinflammatory cytokines by activating the NF-κB signaling pathway.

IL-17B: A new area of study in the IL-17 family

The interleukin (IL)-17 superfamily, a relatively new family of cytokines, consists of six ligands (from IL-17A to IL-17F), which bind to five receptor subtypes (from IL-17RA to IL-17RE) and induce downstream signaling. IL-17A, a prototype member of this family, has been reported to be involved in the pathogenesis of allergies, autoimmune diseases, allograft transplantations, and malignancies. Unlike IL-17A, which is mainly produced by T helper 17 cells, IL-17B is widely expressed in various tissues. Recently, the biological function of IL-17B in diseases, particularly tumors, has attracted the attention of researchers. We previously reported that the expression of IL-17RB increased in gastric cancer tissues and demonstrated that IL-17B/IL-17RB signaling plays a critical role in gastric tumor progression. However, studies on IL-17B are scant. In this review, we detail the structural characteristics, expression patterns, and biological activities of IL-17B and its potential role in the pathogenesis of diseases.

Interleukin-25 Produced by Synoviocytes Has Anti-inflammatory Effects by Acting As a Receptor Antagonist for Interleukin-17A Function

The production and function of cytokines are highly regulated. One mechanism is the balance between pro- and anti-inflammatory cytokines. As interleukin (IL)-17A and IL-25 share the IL-17RA receptor chain, we hypothesize that IL-25 acts as an IL-17A receptor antagonist and limits its pro-inflammatory effects. The production and expression kinetics of IL-25 and its receptor chains IL-17RA and RB were analyzed in rheumatoid synoviocytes alone or in coculture with peripheral blood mononuclear cells (PBMCs). The effects of autocrine or exogenous IL-25 on synoviocytes were investigated in the presence or not of an anti-IL-25 antibody. To study the regulatory effects of IL-25, synoviocytes and/or PBMCs were exposed to IL-25 before being treated with IL-17A and tumor necrosis factor alpha (TNF-α) alone or combined. IL-25, IL-6, and bioactive IL-17A were quantified in rheumatoid arthritis (RA) patient plasma. Synoviocytes expressed and secreted IL-25, and expressed the two chains of its receptor IL-17RA and IL-17RB. IL-17RB expression was increased by TNF-α. IL-25 production occurred at a delayed time point (5 days) after stimulation with IL-17A and TNF-α. Synoviocytes pretreated with IL-25 were less responsive to IL-17A and TNF-α. PBMCs exposed to IL-25 showed a decreased production of pro-inflammatory mediators, including IL-17A with a 57% decrease; p = 0.002. IL-25 levels were elevated in the plasma of RA patients compared to healthy subjects (p = 0.03). However, these levels are not high enough to inhibit the function of circulating IL-17A. In conclusion, it was shown for the first time that synoviocytes produce IL-25, specifically at late time points and that IL-25 acts as a regulator of IL-17A-driven inflammation, as indicated by in vitro results and in vivo, in a long-term RA patient follow-up. These results may be important when considering IL-17A inhibition.

The Diverse Biological Functions of Neutrophils, Beyond the Defense Against Infections

Polymorphonuclear neutrophils are among the first defense against infection and closely involved in the initiation of inflammatory response. It is well recognized that this function of neutrophils was mainly mediated by phagocytosis, intracellular degradation, releasing of granules, and formation of neutrophil extracellular traps after sensing dangerous stress. However, accumulating data showed that neutrophils had a variety of important biological functions in both innate and adaptive immunities, far beyond cytotoxicity against pathogens. Neutrophils can differentially switch phenotypes and display distinct subpopulations under different microenvironments. Neutrophils can produce a large variety of cytokines and chemokines upon stimulation. Furthermore, neutrophils directly interact with dendritic cells (DCs), macrophages, natural killer cells, T cells, and B cells so as to either potentiate or down-modulate both innate and adaptive immunity. In the present review, we summarize the recent progress on the functional plasticity and the regulatory ability on immunity of neutrophils in physiological and pathological situations.

Synovial fibroblast-neutrophil interactions promote pathogenic adaptive immunity in rheumatoid arthritis

Rheumatoid arthritis (RA) is characterized by synovial joint inflammation and by development of pathogenic humoral and cellular autoimmunity to citrullinated proteins. Neutrophil extracellular traps (NETs) are a source of citrullinated autoantigens and activate RA synovial fibroblasts (FLS), cells crucial in joint damage. We investigated the molecular mechanisms by which NETs promote proinflammatory phenotypes in FLS, and whether these interactions generate pathogenic anti-citrulline adaptive immune responses. NETs containing citrullinated peptides are internalized by FLS through a RAGE-TLR9 pathway promoting FLS inflammatory phenotype and their upregulation of MHC class II. Once internalized, arthritogenic NET-peptides are loaded into FLS MHC class II and presented to Ag-specific T cells. HLADRB1*0401 transgenic mice immunized with mouse FLS loaded with NETs develop antibodies specific to citrullinated forms of relevant RA autoantigens implicated in RA pathogenesis as well as cartilage damage. These results implicate FLS as mediators in RA pathogenesis, through the internalization and presentation of NET citrullinated peptides to the adaptive immune system leading to pathogenic autoimmunity and cartilage damage.

Neutrophil azurophilic granule exocytosis is primed by TNF-α and partially regulated by NADPH oxidase

Neutrophil (polymorphonuclear leukocyte) activation with release of granule contents plays an important role in the pathogenesis of acute lung injury, prompting clinical trials of inhibitors of neutrophil elastase. Despite mounting evidence for neutrophil-mediated host tissue damage in a variety of disease processes, mechanisms regulating azurophilic granule exocytosis at the plasma membrane, and thus release of elastase and other proteases, are poorly characterized. We hypothesized that azurophilic granule exocytosis would be enhanced under priming conditions similar to those seen during acute inflammatory events and during chronic inflammatory disease, and selected the cytokine TNF-α to model this in vitro. Neutrophils stimulated with TNF-α alone elicited intracellular reactive oxygen species (ROS) generation and mobilization of secretory vesicles, specific, and gelatinase granules. p38 and ERK1/2 MAPK were involved in these components of priming. TNF-α priming alone did not mobilize azurophilic granules to the cell surface, but did markedly increase elastase release into the extracellular space in response to secondary stimulation with N-formyl-Met-Leu-Phe (fMLF). Priming of fMLF-stimulated elastase release was further augmented in the absence of NADPH oxidase-derived ROS. Our findings provide a mechanism for host tissue damage during neutrophil-mediated inflammation and suggest a novel anti-inflammatory role for the NADPH oxidase.

The Association Between Neutrophil/Lymphocyte Ratio and Disease Activity in Rheumatoid Arthritis and Ankylosing Spondylitis

BACKGROUND

Elevated neutrophil count is associated with poor prognosis and increased mortality in many conditions. Neutrophil to lymphocyte ratio (NLR) has emerged as a marker of inflammation in neoplastic and cardiovascular disorders. Herein, we investigated utility of this simple tool in rheumatoid arthritis (RA) and ankylosing spondylitis (AS).

METHODS

The study consisted of 136 RA and 140 AS patients, along with 117 healthy control subjects. RA and AS activities were determined with Disease Activity Score (DAS) and Bath Ankylosing Spondylitis Disease Activity indices (BASDAI), respectively. The association between NLR and disease activity was analyzed.

RESULTS

Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and neutrophil counts were significantly higher in RA and AS patients compared to healthy controls. Similarly, NLR was higher compared to control subjects, both in RA (2.53 ± 1.4 vs. 2.16 ± 1.0, P = 0.019) and AS (2.43 ± 1.4 vs. 2.16 ± 1.0, P = 0.077). NLR correlated well with ESR and CRP, both in RA and AS. Moreover, NLR increased across worsening DAS28 activity groups (2.1 ± 1.0 in patients with remission, 2.5 ± 1.0 in low-moderate, 3.8 ± 2.5 in high disease activity). However, no association was found between NLR and BASDAI.

CONCLUSION

NLR is a cheap and readily available marker for the assessment of disease activity in RA.

F4+ ETEC infection and oral immunization with F4 fimbriae elicits an IL-17-dominated immune response

Enterotoxigenic Escherichia coli (ETEC) are an important cause of post-weaning diarrhea (PWD) in piglets. Porcine-specific ETEC strains possess different fimbrial subtypes of which F4 fimbriae are the most frequently associated with ETEC-induced diarrhea in piglets. These F4 fimbriae are potent oral immunogens that induce protective F4-specific IgA antibody secreting cells at intestinal tissues. Recently, T-helper 17 (Th17) cells have been implicated in the protection of the host against extracellular pathogens. However, it remains unknown if Th17 effector responses are needed to clear ETEC infections. In the present study, we aimed to elucidate if ETEC elicits a Th17 response in piglets and if F4 fimbriae trigger a similar response. F4⁺ ETEC infection upregulated IL-17A, IL-17F, IL-21 and IL-23p19, but not IL-12 and IFN-γ mRNA expression in the systemic and mucosal immune system. Similarly, oral immunization with F4 fimbriae triggered a Th17 signature evidenced by an upregulated mRNA expression of IL-17F, RORγt, IL-23p19 and IL-21 in the peripheral blood mononuclear cells (PBMCs). Intriguingly, IL-17A mRNA levels were unaltered. To further evaluate this difference between systemic and mucosal immune responses, we assayed the cytokine mRNA profile of F4 fimbriae stimulated PBMCs. F4 fimbriae induced IL-17A, IL-17F, IL-22 and IL-23p19, but downregulated IL-17B mRNA expression. Altogether, these data indicate a Th17 dominated response upon oral immunization with F4 fimbriae and F4⁺ ETEC infection. Our work also highlights that IL-17B and IL-17F participate in the immune response to protect the host against F4⁺ ETEC infection and could aid in the design of future ETEC vaccines.

Innate immunity sensors participating in pathophysiology of joint diseases: a brief overview

The innate immune system consists of functionally specialized "modules" that are activated in response to a particular set of stimuli via sensors located on the surface or inside the tissue cells. These cells screen tissues for a wide range of exogenous and endogenous danger/damage-induced signals with the aim to reject or tolerate them and maintain tissue integrity. In this line of thinking, inflammation evolved as an adaptive tool for restoring tissue homeostasis. A number of diseases are mediated by a maladaptation of the innate immune response, perpetuating chronic inflammation and tissue damage. Here, we review recent evidence on the cross talk between innate immune sensors and development of rheumatoid arthritis, osteoarthritis, and aseptic loosening of total joint replacements. In relation to the latter topic, there is a growing body of evidence that aseptic loosening and periprosthetic osteolysis results from long-term maladaptation of periprosthetic tissues to the presence of by-products continuously released from an artificial joint.

Macrophage polarization and activation in response to implant debris: influence by "particle disease" and "ion disease"

Macrophages derive from human embryonic and fetal stem cells and from human bone marrow-derived blood monocytes. They play a major homeostatic role in tissue remodeling and maintenance facilitated by apoptotic "eat me" opsonins like CRP, serum amyloid P, C1q, C3b, IgM, ficolin, and surfactant proteins. Three subsets of monocytes, classic, intermediate, and nonclassic, are mobilized and transmigrate to tissues. Implant-derived wear particles opsonized by danger signals regulate macrophage priming, polarization (M1, M2, M17, and Mreg), and activation. CD14(+) monocytes in healthy controls and CD16(+) monocytes in inflammation differentiate/polarize to foreign body giant cells/osteoclasts or inflammatory dendritic cells (infDC). These danger signal opsonins can be pathogen- or microbe-associated molecular patterns (PAMPs/MAMPs), but in aseptic loosening, usually are damage-associated molecular patterns (DAMPs). Danger signal-opsonized particles elicit "particle disease" and aseptic loosening. They provide soluble and cell membrane-bound co-stimulatory signals that can lead to cell-mediated immune reactions to metal ions. Metal-on-metal implant failure has disclosed that quite like Ni(2+), its neighbor in the periodic table Co(2+) can directly activate toll-like receptor 4 (TLR4) as a lipopolysaccharide-mimic. "Ion disease" concept needs to be incorporated into the "particle disease" concept, due to the toxic, immune, and inflammatory potential of metal ions.

Human umbilical cord mesenchymal stem cells improve the immune-associated inflammatory and prothrombotic state in collagen type-Ⅱ-induced arthritic rats

Human umbilical cord mesenchymal stem cells (hUC‑MSCs) hold great potential in the search for therapies to treat refractory diseases, including rheumatoid arthritis (RA), due to their potential regenerative ability and extensive source. However, the role of hUC‑MSCs in vivo and the repair mechanisms for RA remain to be fully elucidated. The present study aimed to determine whether hUC‑MSCs exert immunomodulatory effects and have anti‑inflammatory capabilities in the treatment of embolisms. Following the transplantation of hUC‑MSCs into collagen type Ⅱ‑induced arthritic (CIA) model rats, magnetic resonance imaging (MRI) in vivo was performed, and the levels of interleukin (IL)‑1, IL‑17, tumor necrosis factor (TNF)‑α, vascular endothelial growth factor (VEGF), tissue factor (TF), CD4+CD25+ T cells (Treg) and antithrombin (AT) were measured. Bromodeoxyuridine staining was performed for histopathological examinations. As revealed by immunofluorescence and MRI experiments, the injected hUC‑MSCs preferentially migrated to the inflammatory joint sites of the rats. The Treg cell percentage and AT levels in the hUC‑MSC‑treated group were markedly increased, whereas the levels of IL‑1, IL‑17, TNF‑α, VEGF and TF were decreased compared with those in the CIA model group. The values determined for these parameters in the hUC‑MSC‑treated group returned to approximately the identical values as those of the control group on day 35 post‑therapy. Superparamagnetic iron oxide nanoparticles (SPIONs) may serve as an effective, non‑invasive method for tracking transplanted cells in vivo. The present study provided direct evidence that hUC‑MSCs in the CIA rat model migrated to the inflammatory joint sites, effectively promoting recovery from collagen type II damage and thereby improving the immune‑associated prothrombotic state.

Distinctive expression pattern of interleukin-17 cytokine family members in colorectal cancer

Colorectal cancer (CRC) is one of the most common cancers in both genders. Even though interleukin (IL)-17A was shown to play an important role in intestinal tumourigenesis and CRC, other IL-17 family members were not studied well. We therefore studied the expression of IL-17 cytokine family members in CRC. Ten healthy colons and ten CRC mucosa were immunostained for IL-17B, IL-17C, IL-17E, and IL-17F, and their receptors IL-17RA, IL-17RB, and IL-17RC. Double immunofluorescence staining of the CRC mucosa was done for IL-17B with markers of neutrophils, endothelial cells, macrophages, T cells, mast cells, or fibroblasts. While IL-17B was increased in CRC with a strong presence both in the epithelial and stromal compartments, IL-17C showed different expression depending on the grade of differentiation and IL-17E remained unchanged. In contrast, IL-17F was decreased in CRC compared to healthy control. Colon epithelial cells stained positive for IL-17RA, IL-17RB, and IL-17RC in both healthy control and CRC. Neutrophils were the main source of IL-17B in the stroma. IL-17 family members demonstrated distinct expression patterns in CRC, suggesting a differential role exerted by each member in colon carcinogenesis.

The danger model approach to the pathogenesis of the rheumatic diseases

The danger model was proposed by Polly Matzinger as complement to the traditional self-non-self- (SNS-) model to explain the immunoreactivity. The danger model proposes a central role of the tissular cells' discomfort as an element to prime the immune response processes in opposition to the traditional SNS-model where foreignness is a prerequisite. However recent insights in the proteomics of diverse tissular cells have revealed that under stressful conditions they have a significant potential to initiate, coordinate, and perpetuate autoimmune processes, in many cases, ruling over the adaptive immune response cells; this ruling potential can also be confirmed by observations in several genetically manipulated animal models. Here, we review the pathogenesis of rheumatic diseases such as systemic lupus erythematous, rheumatoid arthritis, spondyloarthritis including ankylosing spondylitis, psoriasis, and Crohn's disease and provide realistic approaches based on the logic of the danger model. We assume that tissular dysfunction is a prerequisite for chronic autoimmunity and propose two genetically conferred hypothetical roles for the tissular cells causing the disease: (A) the Impaired cell and (B) the paranoid cell. Both roles are not mutually exclusive. Some examples in human disease and in animal models are provided based on current evidence.