IL-17C is a driver of damaging inflammation during Neisseria gonorrhoeae infection of human Fallopian tube.

The human pathogen Neisseria gonorrhoeae ascends into the upper female reproductive tract to cause damaging inflammation within the Fallopian tubes and pelvic inflammatory disease (PID), increasing the risk of infertility and ectopic pregnancy. The loss of ciliated cells from the epithelium is thought to be both a consequence of inflammation and a cause of adverse sequelae. However, the links between infection, inflammation, and ciliated cell extrusion remain unresolved. With the use of ex vivo cultures of human Fallopian tube paired with RNA sequencing we defined the tissue response to gonococcal challenge, identifying cytokine, chemokine, cell adhesion, and apoptosis related transcripts not previously recognized as potentiators of gonococcal PID. Unexpectedly, IL-17C was one of the most highly induced genes. Yet, this cytokine has no previous association with gonococcal infection nor pelvic inflammatory disease and thus it was selected for further characterization. We show that human Fallopian tubes express the IL-17C receptor on the epithelial surface and that treatment with purified IL-17C induces pro-inflammatory cytokine secretion in addition to sloughing of the epithelium and generalized tissue damage. These results demonstrate a previously unrecognized but critical role of IL-17C in the damaging inflammation induced by gonococci in a human explant model of PID.

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

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

The IL-17 pathway intertwines with neurotrophin and TLR/IL-1R pathways since its domain shuffling origin.

The IL-17 pathway displays remarkably diverse functional modes between different subphyla, classes, and even orders, yet its driving factors remains elusive. Here, we demonstrate that the IL-17 pathway originated through domain shuffling between a Toll-like receptor (TLR)/IL-1R pathway and a neurotrophin-RTK (receptor-tyrosine-kinase) pathway (a Trunk-Torso pathway). Unlike other new pathways that evolve independently, the IL-17 pathway remains intertwined with its donor pathways throughout later evolution. This intertwining not only influenced the gains and losses of domains and components in the pathway but also drove the diversification of the pathway's functional modes among animal lineages. For instance, we reveal that the crustacean female sex hormone, a neurotrophin inducing sex differentiation, could interact with IL-17Rs and thus be classified as true IL-17s. Additionally, the insect prothoracicotropic hormone, a neurotrophin initiating ecdysis in Drosophila by binding to Torso, could bind to IL-17Rs in other insects. Furthermore, IL-17R and TLR/IL-1R pathways maintain crosstalk in amphioxus and zebrafish. Moreover, the loss of the Death domain in the pathway adaptor connection to IκB kinase and stress-activated protein kinase (CIKSs) dramatically reduced their abilities to activate nuclear factor-kappaB (NF-κB) and activator protein 1 (AP-1) in amphioxus and zebrafish. Reinstating this Death domain not only enhanced NF-κB/AP-1 activation but also strengthened anti-bacterial immunity in zebrafish larvae. This could explain why the mammalian IL-17 pathway, whose CIKS also lacks Death, is considered a weak signaling activator, relying on synergies with other pathways. Our findings provide insights into the functional diversity of the IL-17 pathway and unveil evolutionary principles that could govern the pathway and be used to redesign and manipulate it.

Involvement of IL-17 A/IL-17 Receptor A with Neutrophil Recruitment and the Severity of Coronary Arteritis in Kawasaki Disease.

PURPOSE: To assess the role of the interleukin (IL)-17 A/IL-17 receptor A (IL-17RA) in Kawasaki disease (KD)-related coronary arteritis (CA). METHODS: In human study, the plasma levels of IL-17 A and coronary arteries were concurrently examined in acute KD patients. In vitro responses of human coronary endothelial cells to plasma stimulation were investigated with and without IL-17RA neutralization. A murine model of Lactobacillus casei cell-wall extract (LCWE)-induced CA using wild-type Balb/c and Il17ra-deficient mice were also inspected. RESULTS: The plasma levels of IL-17 A were significantly higher in KD patients before intravenous immunoglobulin therapy, especially in those with coronary artery lesion. The pre-IVIG IL-17 A levels positively correlated with maximal z scores of coronary diameters and plasma-induced endothelial mRNA levels of chemokine (C-X-C motif) ligand-1, IL-8, and IL-17RA. IL-17RA blockade significantly reduced such endothelial upregulations of aforementioned three genes and inducible nitric oxide synthase, and neutrophil transmigration. IL-17RA expression was enhanced on peripheral blood mononuclear cells in pre-IVIG KD patients, and in the aortic rings and spleens of the LCWE-stimulated mice. LCWE-induced CA composed of dual-positive Ly6G- and IL-17 A-stained infiltrates. Il17ra-deficient mice showed reduced CA severity with the fewer number of neutrophils and lower early inducible nitric oxide synthase and chemokine (C-X-C motif) ligand-1 mRNA expressions than Il17ra+/+ littermates, and absent IL-17RA upregulation at aortic roots. CONCLUSION: IL-17 A/IL-17RA axis may play a role in mediating aortic neutrophil chemoattraction, thus contributory to the severity of CA in both humans and mice. These findings may help to develop a new therapeutic strategy toward ameliorating KD-related CA.

Association of interleukin-17A and chemokine/vascular endothelial growth factor-induced angiogenesis in newly diagnosed patients with bladder cancer.

BACKGROUND: The human interleukin-17 (IL-17) family comprises IL-17A to IL-17 F; their receptors are IL-17RA to IL-17RE. Evidence revealed that these cytokines can have a tumor-supportive or anti-tumor impact on human malignancies. The purpose of this study was to assess the expression of CXCR2, IL-17RA, and IL-17RC genes at the mRNA level as well as tissue and serum levels of IL-17A, vascular endothelial growth factor (VEGF), and transforming growth factor ß (TGF-ß) in patients with bladder cancer (BC) compared to control. RESULTS: This study showed that gene expression of IL-17RA, IL-17RC, and CXCR2 in the tumoral tissue of BC patients was significantly upregulated compared with normal tissue. The findings disclosed a significant difference in the serum and tissue concentrations of IL-17A, VEGF, and TGF-ß between the patient and the control groups, as well as tumor and normal tissues. CONCLUSION: This study reveals notable dysregulation of CXCR2, IL-17RA, and IL-17RC genes, alongside changes in IL-17A, VEGF, and TGF-ß levels in patients with BC than in controls. These findings indicate their possible involvement in BC development and their potential as diagnostic and therapeutic targets.

Suppression of TCF4 promotes a ZC3H12A-mediated self-sustaining inflammatory feedback cycle involving IL-17RA/IL-17RE epidermal signaling.

IL-17C is an epithelial cell-derived proinflammatory cytokine whose transcriptional regulation remains unclear. Analysis of the IL17C promoter region identified TCF4 as putative regulator, and siRNA knockdown of TCF4 in human keratinocytes (KCs) increased IL17C. IL-17C stimulation of KCs (along with IL-17A and TNF-α stimulation) decreased TCF4 and increased NFKBIZ and ZC3H12A expression in an IL-17RA/RE-dependent manner, thus creating a feedback loop. ZC3H12A (MCPIP1/Regnase-1), a transcriptional immune-response regulator, also increased following TCF4 siRNA knockdown, and siRNA knockdown of ZC3H12A decreased NFKBIZ, IL1B, IL36G, CCL20, and CXCL1, revealing a proinflammatory role for ZC3H12A. Examination of lesional skin from the KC-Tie2 inflammatory dermatitis mouse model identified decreases in TCF4 protein concomitant with increases in IL-17C and Zc3h12a that reversed following the genetic elimination of Il17c, Il17ra, and Il17re and improvement in the skin phenotype. Conversely, interference with Tcf4 in KC-Tie2 mouse skin increased Il17c and exacerbated the inflammatory skin phenotype. Together, these findings identify a role for TCF4 in the negative regulation of IL-17C, which, alone and with TNF-α and IL-17A, feed back to decrease TCF4 in an IL-17RA/RE-dependent manner. This loop is further amplified by IL-17C-TCF4 autocrine regulation of ZC3H12A and IL-17C regulation of NFKBIZ to promote self-sustaining skin inflammation.

Endothelial IL17RD promotes Western diet-induced aortic myeloid cell infiltration.

The Interleukin-17 (IL17) family is a group of cytokines implicated in the etiology of several inflammatory diseases. Interleukin-17 receptor D (IL17RD), also known as Sef (similar expression to fibroblast growth factor) belonging to the family of IL17 receptors, has been shown to modulate IL17A-associated inflammatory phenotypes. The objective of this study was to test the hypothesis that IL17RD promotes endothelial cell activation and consequent leukocyte adhesion. We utilized primary human aortic endothelial cells and demonstrated that RNAi targeting of IL17RD suppressed transcript levels by 83 % compared to non-targeted controls. Further, RNAi knockdown of IL17RD decreased the adhesion of THP-1 monocytic cells onto a monolayer of aortic endothelial cells in response to IL17A. Additionally, we determined that IL17A did not significantly enhance the activation of canonical MAPK and NFκB pathways in endothelial cells, and further did not significantly affect the expression of VCAM-1 and ICAM-1 in aortic endothelial cells, which is contrary to previous findings. We also determined the functional relevance of our findings in vivo by comparing the expression of endothelial VCAM-1 and ICAM-1 and leukocyte infiltration in the aorta in Western diet-fed Il17rd null versus wild-type mice. Our results showed that although Il17rd null mice do not have significant alteration in aortic expression of VCAM-1 and ICAM-1 in endothelial cells, they exhibit decreased accumulation of proinflammatory monocytes and neutrophils, suggesting that endothelial IL17RD induced in vivo myeloid cell accumulation is not dependent on upregulation of VCAM-1 and ICAM-1 expression. We further performed proteomics analysis to identify potential molecular mediators of the IL17A/IL17RD signaling axis. Collectively, our results underscore a critical role for Il17rd in the regulation of aortic myeloid cell infiltration in the context of Western diet feeding.

SELEX-discovered aptamer that inhibits cellular interleukin-17/interleukin-17 receptor interaction and antagonizes interleukin-17 signaling.

This research is based on a Systematic Evolution of Ligands by EXponential enrichment, also referred to as in vitro selection against the extracellular domain of human interleukin-17 receptor A (IL-17RA). Pull-down assay via quantitative polymerase chain reaction and chemiluminescence detection showed that the cloned RNA with the enriched sequence bound to human IL-17RA and inhibited the interaction between IL-17RA and human interleukin-17A (IL-17A). We also revealed that the newly discovered IL-17RA-binding RNA aptamer bound to cellular IL-17RA, inhibited the cellular IL-17RA/IL-17A interaction, and antagonized cellular IL-17A signaling.

IL-17 receptor A functions to help maintain barrier integrity and limit activation of immunopathogenic response to H. pylori infection.

Activation of Th17 cell responses, including the production of IL-17A and IL-21, contributes to host defense and inflammatory responses by coordinating adaptive and innate immune responses. IL-17A and IL-17F signal through a multimeric receptor, which includes the IL-17 receptor A (IL-17RA) subunit and the IL-17RC subunit. IL-17RA is expressed by many cell types, and data from previous studies suggest that loss of IL-17 receptor is required to limit immunopathology in the Helicobacter pylori model of infection. Here, an Il17ra-/- mouse was generated on the FVB/n background, and the role of IL-17 signaling in the maintenance of barrier responses to H. pylori was investigated. Generating the Il17ra-/- on the FVB/n background allowed for the examination of responses in the paragastric lymph node and will allow for future investigation into carcinogenesis. While uninfected Il17ra-/- mice do not develop spontaneous gastritis following H. pylori infection, Il17ra-/- mice develop severe gastric inflammation accompanied by lymphoid follicle production and exacerbated production of Th17 cytokines. Increased inflammation in the tissue, increased IgA levels in the lumen, and reduced production of Muc5ac in the corpus correlate with increased H. pylori-induced paragastric lymph node activation. These data suggest that the cross talk between immune cells and epithelial cells regulates mucin production, IgA production, and translocation, impacting the integrity of the gastric mucosa and therefore activating of the adaptive immune response.

Gut epithelial Interleukin-17 receptor A signaling can modulate distant tumors growth through microbial regulation.

Microbes influence cancer initiation, progression and therapy responsiveness. IL-17 signaling contributes to gut barrier immunity by regulating microbes but also drives tumor growth. A knowledge gap remains regarding the influence of enteric IL-17-IL-17RA signaling and their microbial regulation on the behavior of distant tumors. We demonstrate that gut dysbiosis induced by systemic or gut epithelial deletion of IL-17RA induces growth of pancreatic and brain tumors due to excessive development of Th17, primary source of IL-17 in human and mouse pancreatic ductal adenocarcinoma, as well as B cells that circulate to distant tumors. Microbial dependent IL-17 signaling increases DUOX2 signaling in tumor cells. Inefficacy of pharmacological inhibition of IL-17RA is overcome with targeted microbial ablation that blocks the compensatory loop. These findings demonstrate the complexities of IL-17-IL-17RA signaling in different compartments and the relevance for accounting for its homeostatic host defense function during cancer therapy.

Genetic association between interleukin-17 and susceptibility to rheumatoid arthritis.

BACKGROUND: The pathogenesis of rheumatoid arthritis (RA) is an immune imbalance, in which various inflammatory immune cells and pro-inflammatory factors are involved. Interleukin-17 (IL-17), a potent pro-inflammatory cytokine, has been found to have increased expression in the joints of patients with RA compared to healthy individuals. However, the causal relationship between the expression level of IL-17 or IL-17 receptor (IL-17R) and RA remained unknown. In this study, two-sample Mendelian randomization (MR) was used to investigate the causal relationship between IL-17 and RA. METHODS: Summary statistics for RA (14,361 RA cases and 43,923 healthy controls) and IL-17 (3,301 samples) were obtained from an available meta-analysis of published genome-wide association studies (GWAS). Relevant single nucleotide polymorphisms (SNPs) were selected by executing quality control steps from the GWAS summary results. Then we used bi-directional two-sample Mendelian randomization (MR) and multi-variable MR (MVMR) analysis to examine evidence of causality. MR and MVMR analyses progressed mainly using inverse variance weighted (IVW), weighted median (WM), and MR-Egger regression methods, which were applied to the genetic instrumental variables (IVs) of IL-17A/IL-17 RA, IL-17C/IL-17 RC, and IL-17D/IL-17RD and RA. For assessing the robustness of the results, we also carried out a sensitivity analysis to assess heterogeneity and pleiotropy, such as MR-Egger, leave-one-out, and MR pleiotropy residual sum and outlier (MR-PRESSO). RESULTS: Two-sample MR Analysis showed the causal relationship between IL-17A/IL-17RA and RA. The presence of genetically high IL-17A/IL-17RA may increase the risk of RA (IL-17A(OR = 1.095; 95% C.I., 0.990-1.210, p.adj = 0.013), IL-17RA(OR = 1.113, 95%CI = 1.006-1.231, p.adj = 0.006)). However, the results indicated that IL-17C/IL-17RC, and IL-17D/IL-17RD demonstrated no causal impact on RA (IL-17C(OR = 1.007, 95%CI = 0.890-1.139, p.adj = 0.152), IL-17RC(OR = 1.006, 95%CI = 0.904-1.119, p.adj = 0.152), IL-17D(OR = 0.979, 95%CI = 0.843-1.137, p.adj = 0.130), IL-17RD(OR = 0.983, 95%CI = 0.876-1.104, p.adj = 0.129)). Furthermore, MVMR analysis shown that IL-17RA(OR = 1.049, 95% CI: 0.997-1.102, p.adj = 0.014) was associated with increased risk of RA. Sensitivity analysis showed no heterogeneity and pleiotropy, suggesting that the above results were robust and reliable. CONCLUSION: The MR analysis provides evidence that IL-17A/IL-17RA are risk factors for RA. This emphasizes the importance of intervention on IL-17A/IL-17RA in patients with RA. Developing drugs that limit IL-17A may reduce the risk of RA.

Interleukin-17 signaling influences CD8+ T cell immunity and tumor progression according to the IL-17 receptor subunit expression pattern in cancer cells.

IL-17 immune responses in cancer are controversial, with both tumor-promoting and tumor-repressing effects observed. To clarify the role of IL-17 signaling in cancer progression, we used syngeneic tumor models from different tissue origins. We found that deficiencies in host IL-17RA or IL-17A/F expression had varying effects on the in vivo growth of different solid tumors including melanoma, sarcoma, lymphoma, and leukemia. In each tumor type, the absence of IL-17 led to changes in the expression of mediators associated with inflammation and metastasis in the tumor microenvironment. Furthermore, IL-17 signaling deficiencies in the hosts resulted in decreased anti-tumor CD8+ T cell immunity and caused tumor-specific changes in several lymphoid cell populations. Our findings were associated with distinct patterns of IL-17A/F cytokine and receptor subunit expression in the injected tumor cell lines. These patterns affected tumor cell responsiveness to IL-17 and downstream intracellular signaling, leading to divergent effects on cancer progression. Additionally, we identified IL-17RC as a critical determinant of the IL-17-mediated response in tumor cells and a potential biomarker for IL-17 signaling effects in tumor progression. Our study offers insight into the molecular mechanisms underlying IL-17 activities in cancer and lays the groundwork for developing personalized immunotherapies.

SARS-CoV-2 ORF8 Mediates Signals in Macrophages and Monocytes through MyD88 Independently of the IL-17 Receptor.

SARS-CoV-2 has caused an estimated 7 million deaths worldwide to date. A secreted SARS-CoV-2 accessory protein, known as open reading frame 8 (ORF8), elicits inflammatory pulmonary cytokine responses and is associated with disease severity in COVID-19 patients. Recent reports proposed that ORF8 mediates downstream signals in macrophages and monocytes through the IL-17 receptor complex (IL-17RA, IL-17RC). However, generally IL-17 signals are found to be restricted to the nonhematopoietic compartment, thought to be due to rate-limiting expression of IL-17RC. Accordingly, we revisited the capacity of IL-17 and ORF8 to induce cytokine gene expression in mouse and human macrophages and monocytes. In SARS-CoV-2-infected human and mouse lungs, IL17RC mRNA was undetectable in monocyte/macrophage populations. In cultured mouse and human monocytes and macrophages, ORF8 but not IL-17 led to elevated expression of target cytokines. ORF8-induced signaling was fully preserved in the presence of anti-IL-17RA/RC neutralizing Abs and in Il17ra-/- cells. ORF8 signaling was also operative in Il1r1-/- bone marrow-derived macrophages. However, the TLR/IL-1R family adaptor MyD88, which is dispensable for IL-17R signaling, was required for ORF8 activity yet MyD88 is not required for IL-17 signaling. Thus, we conclude that ORF8 transduces inflammatory signaling in monocytes and macrophages via MyD88 independently of the IL-17R.

Association between IL-17F, IL-17RA Gene Polymorphisms and Response to Biological Drugs in Psoriasis and Beyond.

Psoriasis is a systemic inflammatory disease that associates with multiple comorbidities. It involves complex interactions between environmental factors and polygenic predisposition. The IL-17 family is one of the main actors in the pathogenesis of psoriasis. Secondary nonresponse is common, especially during the long-term use of TNF-α inhibitors, but it is not uncommon even for newer biologics, such as IL-17 inhibitors. Identification of clinically useful biomarkers of treatment efficacy and safety would enable optimal treatment selection, improve patient quality of life and outcome, and reduce healthcare costs. To our knowledge, this is the first study to evaluate the relationship between genetic polymorphism of IL-17F (rs763780) and IL-17RA (rs4819554) and response to biological treatment and other clinical data in bio-naive and secondary non-responders psoriasis patients in Romania and Southeastern Europe. We performed a prospective, longitudinal, analytical cohort study of 81 patients diagnosed with moderate-to-severe chronic plaque psoriasis who received biological treatments for the first time. Of the 79 patients treated with TNF-α inhibitors, 44 experienced secondary nonresponse. All patients were genotyped for the two SNPs in IL-17F and IL-17RA genes. The rs763780 polymorphism in the IL-17F gene could be an attractive candidate biomarker for predicting which patients will respond to anti-TNF-α therapies. Another emergent association of rs4819554 in IL-17RA with the risk of nail psoriasis and a higher BMI in moderate-to-severe plaque psoriasis patients is described.

Immunogenic Cell Death Associated Molecular Patterns and the Dual Role of IL17RA in Interstitial Cystitis/Bladder Pain Syndrome.

The unclear etiology and pathogenesis of interstitial cystitis/bladder pain syndrome (IC/BPS) are responsible for the lack of effective treatment and the poor patient prognosis. Various studies show that chronic inflammation and immune responses are important factors contributing to the pathogenesis of IC/BPS. The process of immunogenic cell death (ICD) involves both the immune response and inflammatory process, and the involvement of ICD in IC/BPS pathogenesis has not been explored. Two IC/BPS transcriptome datasets collected from the Gene Expression Omnibus (GEO) database were used to identify distinct ICD-associated molecular patterns (IAMPs). IAMPs and IC/BPS subtypes were found to be related. The inflammatory immune microenvironments (IIME) in different IAMPs were studied. The potential mechanism by which the interleukin 17 receptor A (IL17RA) influences IC/BPS was examined using in vitro assays. The expression of ICD-related genes (IRGs) was upregulated in IC/BPS bladders, compared with normal bladders. Disease prediction models, based on differentially expressed IRGs, could accurately predict IC/BPS. The IC/BPS patients had two distinct IAMPs, each with its own subtype and clinical features and association with remodeling IIME. IL17RA, a well-established IC/BPS bladder biomarker, mediates both the inflammatory insult and the protective responses. In summary, the current study identified different IAMPs in IC/BPS, which may be involved in the pathogenesis of IC/BPS by remodeling the IIME. The chronic inflammatory process in IC/BPS may be prolonged by IL17RA, which could mediate both pro- and anti-inflammatory responses. The IL17RA-associated pathway may play a significant role in the development of IC/BPS and can be used as a therapeutic target.

IL-17-driven induction of Paneth cell antimicrobial functions protects the host from microbiota dysbiosis and inflammation in the ileum.

Interleukin (IL)-17 protects epithelial barriers by inducing the secretion of antimicrobial peptides. However, the effect of IL-17 on Paneth cells (PCs), the major producers of antimicrobial peptides in the small intestine, is unclear. Here, we show that the targeted ablation of the IL-17 receptor (IL-17R) in PCs disrupts their antimicrobial functions and decreases the frequency of ileal PCs. These changes become more pronounced after colonization with IL-17 inducing segmented filamentous bacteria. Mice with PCs that lack IL-17R show an increased inflammatory transcriptional profile in the ileum along with the severity of experimentally induced ileitis. These changes are associated with a decrease in the diversity of gut microbiota that induces a severe ileum pathology upon transfer to genetically susceptible mice, which can be prevented by the systemic administration of IL-17a/f in microbiota recipients. In an exploratory analysis of a small cohort of pediatric patients with Crohn's disease, we have found that a portion of these patients exhibits a low number of lysozyme-expressing ileal PCs and a high ileitis severity score, resembling the phenotype of mice with IL-17R-deficient PCs. Our study identifies IL-17R-dependent signaling in PCs as an important mechanism that maintains ileal homeostasis through the prevention of dysbiosis.

IL17A and IL17RA gene polymorphisms in Fanconi anemia.

Fanconi anemia is a rare autosomal recessive disease. In this disease, cytokine pathways can induce the bone marrow failure that is observed in individuals with Fanconi anemia. Interleukin IL-17 exhibits a protective effect in organisms because it induces neutrophil recruitment and shows a pathological role in several models of autoimmune diseases, periodontal disease, cancer, allograft rejection, and graft versus host disease. Polymorphisms in the IL17A and IL17RA genes were evaluated from DNA in saliva, comparing individuals with or without Fanconi anemia, using models of genotypic transmission (additive, dominant, and recessive). Polymorphisms in the IL17A and IL17RA genes (rs2241044 [C allele], rs879577 [C allele], rs9606615 [T allele], and rs2241043 [C allele]) were risk factors for developing Fanconi anemia. We also performed an analysis of gene markers with clinical variables in the Fanconi group. Polymorphisms in the IL17A gene (rs3819025 [A allele] and rs2275913 [G allele], respectively) were associated with an age of less than 20 years (p = 0.026; RP 0.65) and the female sex (p = 0.043; RP 0.88). The IL17RA gene was also associated with age and the presence of leukoplakia (a potentially malignant oral disorder). An age of less than 20 years was associated with rs917864 (T allele; p = 0.036; RP 0.67). The presence of leukoplakia was associated with rs17606615 (T allele; p = 0.042; RP 0.47). To our knowledge, this is the first study that associates IL17A and IL17RA gene polymorphisms with Fanconi anemia and examines rs2241044 polymorphisms in scientific literature thus far.

Associations of IL-17 and IL-17 receptor polymorphisms with Behçet's disease in Denizli Province of Turkey.

Although the etiopathogenesis of Behçet's disease is not known, studies conducted in different populations show that it is a multifactorial disease that is thought to develop as a result of the interaction of environmental and genetic factors. IL-17 is thought to induce the neutrophilic inflammation and the tissue damage mediated by immune response in patients. Polymorphisms in the gene region encoding IL-17 and IL-17R molecules may play a critical role in the pathogenesis of the disease and contribute to the elucidation of disease mechanism. We aimed to show the association of IL-17A, IL-17F, and IL-17RC polymorphisms and haplotypes in Behçet's disease patients and its clinical features. We genotyped IL-17A (rs4711998 (A/G), rs8193036 (C/T), rs2275913 (A/G), rs3819025 (A/G), rs8193038 (A/G), rs3804513 (A/T), rs1974226 (C/T), rs3748067 (C/T)); IL-17F (rs763780 (T/C), rs2397084 (T/C)); and IL-17R (IL-17RC) (rs708567 (C/T)) polymorphisms in 88 patients with Behçet's disease and 133 healthy controls using PCR-RFLP-based approach. The results of our study showed that polymorphisms of IL-17A, rs8193036 (C/T), rs3819025 (G/A), rs3804513 (A/T), IL-17F rs2397084 (T/C), and IL-17RC rs708567 (C/T) are associated with the susceptibility to the BD. When the haplotype distributions of all loci of IL-17Aand IL-17A/IL-17F together were examined and in contrast to the data obtained from the controls, the GTGGAACC (27.84%) and GTGGAACCTT (25.57%) have the highest frequencies. In conclusion, the allele and genotype frequency differences of the IL-17A, IL-17F, and IL-17R and haplotype frequencies between Behçet's disease and controls indicate that the genetic structure of Behçet's disease may be different.

CMTM4 makes IL-17 signaling more complex.

A transmembrane protein promotes the plasma membrane localization and signaling mediated by an IL-17 receptor subunit.

IL-17-induced dimerization of IL-17RA drives the formation of the IL-17 signalosome to potentiate signaling.

Signaling through innate immune receptors such as the Toll-like receptor (TLR)/interleukin-1 receptor (IL-1R) superfamily proceeds via the assembly of large membrane-proximal complexes or "signalosomes." Although structurally distinct, the IL-17 receptor family triggers cellular responses that are typical of innate immune receptors. The IL-17RA receptor subunit is shared by several members of the IL-17 family. Using a combination of crystallographic, biophysical, and mutational studies, we show that IL-17A, IL-17F, and IL-17A/F induce IL-17RA dimerization. X-ray analysis of the heteromeric IL-17A complex with the extracellular domains of the IL-17RA and IL-17RC receptors reveals that cytokine-induced IL-17RA dimerization leads to the formation of a 2:2:2 hexameric signaling assembly. Furthermore, we demonstrate that the formation of the IL-17 signalosome potentiates IL-17-induced IL-36γ and CXCL1 mRNA expression in human keratinocytes, compared with a dimerization-defective IL-17RA variant.