Affinity-coupled CCL22 promotes positive selection in germinal centres.

Antibody affinity maturation depends on positive selection in germinal centres (GCs) of rare B cell clones that acquire higher-affinity B cell receptors via somatic hypermutation, present more antigen to follicular helper T (TFH) cells and, consequently, receive more contact-dependent T cell help1. As these GC B cells and TFH cells do not maintain long-lasting contacts in the chaotic GC environment2-4, it is unclear how sufficient T cell help is cumulatively focused onto those rare clones. Here we show that, upon stimulation of CD40, GC B cells upregulate the chemokine CCL22 and to a lesser extent CCL17. By engaging the chemokine receptor CCR4 on TFH cells, CCL22 and CCL17 can attract multiple helper cells from a distance, thus increasing the chance of productive help. During a GC response, B cells that acquire higher antigen-binding affinities express higher levels of CCL22, which in turn 'highlight' these high-affinity GC B cells. Acute increase or blockade of TFH cells helps to rapidly increase or decrease CCL22 expression by GC B cells, respectively. Therefore, a chemokine-based intercellular reaction circuit links the amount of T cell help that individual B cells have received recently to their subsequent ability to attract more help. When CCL22 and CCL17 are ablated in B cells, GCs form but B cells are not affinity-matured efficiently. When competing with wild-type B cells in the same reaction, B cells lacking CCL22 and CCL17 receive less T cell help to maintain GC participation or develop into bone-marrow plasma cells. By uncovering a chemokine-mediated mechanism that highlights affinity-improved B cells for preferential help from TFH cells, our study reveals a principle of spatiotemporal orchestration of GC positive selection.

Elevated serum TARC levels precede classic Hodgkin lymphoma diagnosis by several years.

Tumor cells in classic Hodgkin lymphoma produce high quantities of the thymus- and activation-related chemokine (TARC). We measured TARC levels in prediagnostic serum samples and found strikingly increased values in the vast majority of patients, as early as 6 years before diagnosis.

Skin-resident dendritic cells mediate postoperative pain via CCR4 on sensory neurons.

Inflammatory pain, such as hypersensitivity resulting from surgical tissue injury, occurs as a result of interactions between the immune and nervous systems with the orchestrated recruitment and activation of tissue-resident and circulating immune cells to the site of injury. Our previous studies identified a central role for Ly6Clow myeloid cells in the pathogenesis of postoperative pain. We now show that the chemokines CCL17 and CCL22, with their cognate receptor CCR4, are key mediators of this response. Both chemokines are up-regulated early after tissue injury by skin-resident dendritic and Langerhans cells to act on peripheral sensory neurons that express CCR4. CCL22, and to a lesser extent CCL17, elicit acute mechanical and thermal hypersensitivity when administered subcutaneously; this response abrogated by pharmacological blockade or genetic silencing of CCR4. Electrophysiological assessment of dissociated sensory neurons from naïve and postoperative mice showed that CCL22 was able to directly activate neurons and enhance their excitability after injury. These responses were blocked using C 021 and small interfering RNA (siRNA)-targeting CCR4. Finally, our data show that acute postoperative pain is significantly reduced in mice lacking CCR4, wild-type animals treated with CCR4 antagonist/siRNA, as well as transgenic mice depleted of dendritic cells. Together, these results suggest an essential role for the peripheral CCL17/22:CCR4 axis in the genesis of inflammatory pain via direct communication between skin-resident dendritic cells and sensory neurons, opening therapeutic avenues for its control.

Rational Design of High Affinity Interaction Between CC Chemokine Binding Protein vCCI and CCL17/TARC.

The poxvirus-derived protein vCCI (viral CC chemokine inhibitor) binds almost all members of the CC chemokine family with nanomolar affinity, inhibiting their pro-inflammatory actions. Understanding the affinity and specificity of vCCI could lead to new anti-inflammatory therapeutics. CCL17, also known as TARC, is unusual among CC chemokines by having only micromolar binding to vCCI. We have used sequence analysis and molecular simulations to determine the cause of this weak binding, which identified several locations in CCL17 where mutations seemed likely to improve binding to vCCI. Based on the aforementioned analysis, we expressed and tested multiple mutants of CCL17. We found two single point mutants V44K and Q45R that increased binding affinity to vCCI by 2-3-fold and, in combination, further improved affinity by 7-fold. The CCL17 triple mutant G17R/V44K/Q45R yielded a Kd of 0.25 ± 0.13 µM, a 68-fold improvement in affinity compared to the complex with wild-type CCL17. A quadruple mutant G17R/V44K/Q45R/R57W showed high affinity (0.59 ± 0.09 µM) compared to the wild type but lower affinity than the triple mutant. This work demonstrates that sequence comparisons and molecular simulations can predict chemokine mutations that increase the level of binding to vCCI, an important first step in developing engineered chemokine inhibitors useful for anti-inflammatory therapy.

EBV+ tumors exploit tumor cell-intrinsic and -extrinsic mechanisms to produce regulatory T cell-recruiting chemokines CCL17 and CCL22.

The Epstein-Barr Virus (EBV) is involved in the etiology of multiple hematologic and epithelial human cancers. EBV+ tumors employ multiple immune escape mechanisms, including the recruitment of immunosuppressive regulatory T cells (Treg). Here, we show some EBV+ tumor cells express high levels of the chemokines CCL17 and CCL22 both in vitro and in vivo and that this expression mirrors the expression levels of expression of the EBV LMP1 gene in vitro. Patient samples from lymphoblastic (Hodgkin lymphoma) and epithelial (nasopharyngeal carcinoma; NPC) EBV+ tumors revealed CCL17 and CCL22 expression of both tumor cell-intrinsic and -extrinsic origin, depending on tumor type. NPCs grown as mouse xenografts likewise showed both mechanisms of chemokine production. Single cell RNA-sequencing revealed in vivo tumor cell-intrinsic CCL17 and CCL22 expression combined with expression from infiltrating classical resident and migratory dendritic cells in a CT26 colon cancer mouse tumor engineered to express LMP1. These data suggest that EBV-driven tumors employ dual mechanisms for CCL17 and CCL22 production. Importantly, both in vitro and in vivo Treg migration was effectively blocked by a novel, small molecule antagonist of CCR4, CCR4-351. Antagonism of the CCR4 receptor may thus be an effective means of activating the immune response against a wide spectrum of EBV+ tumors.

Evaluation of the CCL17/CCL22-CCR4 axis in pediatrics with B-cell acute lymphoblastic leukemia before and after a chemotherapy course.

AIMS: Acute lymphoblastic leukemia (ALL) is the most common type of pediatrics cancer. Chemokines exert different roles in leukemia process through leukocyte recruitment and regulation of disease severity. Due to the prominent roles of chemokine/receptor axes, this study aimed to measure the blood expression levels of CCR4 and their ligands in pediatrics with B-cell ALL (B-ALL). We also evaluated the impact of cytotoxic chemotherapy on this axis. MATERIAL AND METHOD: Thirty children suffering from B-ALL were included in the study and followed up for 30 days after completion of a chemotherapy course. The blood sampling was performed before and after chemotherapy. 30 healthy donors have also entered the study as control subjects. The mRNA expression of CCL17, CCL22 and CCR4 genes was determined by quantitative real-time PCR. The frequency of the peripheral blood mononuclear cells expressing CCR4 (CCR4 + PBMCs) was also evaluated by the flow cytometry method. Moreover, we evaluated the association of the CCL17/CCL22-CCR4 axis with some diagnostic, prognostic and predictive biomarkers in ALL patients. RESULTS: There was overexpression of the CCL17/CCL22-CCR4 axis along with lactate dehydrogenase (LDH) in pediatrics with B-ALL compared to healthy controls. After induction of chemotherapy, the blood expression levels of the CCL17/CCL22-CCR4 axis have reached the levels of healthy controls. The findings for the blood expression levels of CCR4 were also confirmed using flow cytometry. CONCLUSION: The CCL17/CCL22-CCR4 axis can be used as a novel predictive and prognostic biomarker in B-ALL.

CCL17 and CCL19 are markers of disease progression in alveolar echinococcosis.

OBJECTIVES: Alveolar echinococcosis (AE) represents one of the deadliest helminthic infections, characterized by an insidious onset and high lethality. METHODS: This study utilized the Gene Expression Omnibus (GEO) database, applied Weighted Correlation Network Analysis (WGCNA) and Differential Expression Analysis (DEA), and employed the Matthews Correlation Coefficient (MCC) to identify CCL17 and CCL19 as key genes in AE. Immunohistochemistry and immunofluorescence co-localization techniques were used to examine the expression of CCL17 and CCL19 in liver tissue lesions of AE patients. Additionally, a mouse model of multilocular echinococcus larvae infection was developed to study the temporal expression patterns of these genes, along with liver fibrosis and inflammatory responses. RESULTS: The in vitro model simulating echinococcal larva infection mirrored the hepatic microenvironment post-infection with multilocular echinococcal tapeworms. Quantitative RT-PCR analysis showed that liver fibrosis occurred in AE patients, with proximal activation and increased expression of CCL17 and CCL19 over time post-infection. Notably, expression peaked during the late stages of infection. Similarly, F4/80, a macrophage marker, exhibited corresponding trends in expression. Upon stimulation of normal hepatocytes by vesicular larvae in cellular experiments, there was a significant increase in CCL17 and CCL19 expression at 12 h post-infection, mirroring the upregulation observed with F4/80. CONCLUSION: CCL17 and CCL19 facilitate macrophage aggregation via the chemokine pathway and their increased expression correlates with the progression of infection, suggesting their potential as biomarkers for AE progression.

Targeting Monocyte Derived CCL17 Attenuates Murine Crescentic Glomerulonephritis by Affecting Renal CCR4+ Regulatory T-Cell Recruitment.

INTRODUCTION: The chemokine receptor CCR4 is expressed by diverse CD4+ T cell subsets including regulatory T cells (Tregs) but its functional importance for leukocyte recruitment and the relevance of its two corresponding chemokines CCL17 and CCL22 have not been studied in immune-mediated crescentic glomerulonephritis (cGN). METHODS: Utilizing the single-cell RNA sequencing (scRNAseq) data in analyzing leukocytes isolated from both human and murine nephritic kidneys, we identified CCL17 as a potential therapeutic target in immune-mediated renal disease. Using a mouse model of murine cGN, we then delineated the effects of targeting CCL17 by neutralizing antibodies and in Ccl17 gene-deficient mice. RESULTS: Unsupervised scRNAseq analyses identified the CCL17-CCR4 axis as a mechanism potentially involved in renal T-cell migration. Analyses of functional kidney impairment and histopathological kidney damage revealed an attenuation of crescentic GN in anti-CCL17 antibody-treated mice which was corroborated using in Ccl17 gene-deficient mice. Immunohistochemical analyses revealed that these changes were accompanied by an affected renal Treg recruitment in both experimental approaches. CONCLUSION: The chemokine receptor CCR4 and its corresponding chemokine CCL17 are expressed in human and murine cGN and targeting the CCR4-CCL17 axis by neutralizing antibodies as well as Ccl17 gene deficiency led to increased renal Treg recruitment and reduced histological and functional kidney damage in murine cGN.

CCL17 Promotes Colitis-Associated Tumorigenesis Dependent on the Microbiota.

Colorectal cancer is one of the most common cancers and a major cause of mortality. Proinflammatory and antitumor immune responses play critical roles in colitis-associated colon cancer. CCL17, a chemokine of the C-C family and ligand for CCR4, is expressed by intestinal dendritic cells in the steady state and is upregulated during colitis in mouse models and inflammatory bowel disease patients. In this study, we investigated the expression pattern and functional relevance of CCL17 for colitis-associated colon tumor development using CCL17-enhanced GFP-knockin mice. CCL17 was highly expressed by dendritic cells but also upregulated in macrophages and intermediary monocytes in colon tumors induced by exposure to azoxymethane and dextran sodium sulfate. Despite a similar degree of inflammation in the colon, CCL17-deficient mice developed fewer tumors than did CCL17-competent mice. This protective effect was abrogated by cohousing, indicating a dependency on the microbiota. Changes in microbiota diversity and composition were detected in separately housed CCL17-deficient mice, and these mice were more susceptible to azoxymethane-induced early apoptosis in the colon affecting tumor initiation. Immune cell infiltration in colitis-induced colon tumors was not affected by the lack of CCL17. Taken together, our results indicate that CCL17 promotes colitis-associated tumorigenesis by influencing the composition of the intestinal microbiome and reducing apoptosis during tumor initiation.

Tetramerization of STAT5 promotes autoimmune-mediated neuroinflammation.

Signal tranducer and activator of transcription 5 (STAT5) plays a critical role in mediating cellular responses following cytokine stimulation. STAT proteins critically signal via the formation of dimers, but additionally, STAT tetramers serve key biological roles, and we previously reported their importance in T and natural killer (NK) cell biology. However, the role of STAT5 tetramerization in autoimmune-mediated neuroinflammation has not been investigated. Using the STAT5 tetramer-deficient Stat5a-Stat5b N-domain double knockin (DKI) mouse strain, we report here that STAT5 tetramers promote the pathogenesis of experimental autoimmune encephalomyelitis (EAE). The mild EAE phenotype observed in DKI mice correlates with the impaired extravasation of pathogenic T-helper 17 (Th17) cells and interactions between Th17 cells and monocyte-derived cells (MDCs) in the meninges. We further demonstrate that granulocyte-macrophage colony-stimulating factor (GM-CSF)-mediated STAT5 tetramerization regulates the production of CCL17 by MDCs. Importantly, CCL17 can partially restore the pathogenicity of DKI Th17 cells, and this is dependent on the activity of the integrin VLA-4. Thus, our study reveals a GM-CSF-STAT5 tetramer-CCL17 pathway in MDCs that promotes autoimmune neuroinflammation.

Pharmacological inhibition of MDA-9/Syntenin blocks breast cancer metastasis through suppression of IL-1ß.

Melanoma differentiation associated gene-9 (MDA-9), Syntenin-1, or syndecan binding protein is a differentially regulated prometastatic gene with elevated expression in advanced stages of melanoma. MDA-9/Syntenin expression positively associates with advanced disease stage in multiple histologically distinct cancers and negatively correlates with patient survival and response to chemotherapy. MDA-9/Syntenin is a highly conserved PDZ-domain scaffold protein, robustly expressed in a spectrum of diverse cancer cell lines and clinical samples. PDZ domains interact with a number of proteins, many of which are critical regulators of signaling cascades in cancer. Knockdown of MDA-9/Syntenin decreases cancer cell metastasis, sensitizing these cells to radiation. Genetic silencing of MDA-9/Syntenin or treatment with a pharmacological inhibitor of the PDZ1 domain, PDZ1i, also activates the immune system to kill cancer cells. Additionally, suppression of MDA-9/Syntenin deregulates myeloid-derived suppressor cell differentiation via the STAT3/interleukin (IL)-1ß pathway, which concomitantly promotes activation of cytotoxic T lymphocytes. Biologically, PDZ1i treatment decreases metastatic nodule formation in the lungs, resulting in significantly fewer invasive cancer cells. In summary, our observations indicate that MDA-9/Syntenin provides a direct therapeutic target for mitigating aggressive breast cancer and a small-molecule inhibitor, PDZ1i, provides a promising reagent for inhibiting advanced breast cancer pathogenesis.

Skin TARC/CCL17 increase precedes the development of childhood atopic dermatitis.

BACKGROUND: It is unknown whether skin biomarkers collected in infancy can predict the onset of atopic dermatitis (AD) and be used in future prevention trials to identify children at risk. OBJECTIVES: This study sought to examine whether skin biomarkers can predict AD during the first 2 years of life. METHODS: This study enrolled 300 term and 150 preterm children at birth and followed for AD until the age of 2 years. Skin tape strips were collected at 0 to 3 days and 2 months of age and analyzed for selected immune and barrier biomarkers. Hazard ratio (HR) with 95% confidence interval (CI) using Cox regression was calculated for the risk of AD. RESULTS: The 2-year prevalence of AD was 34.6% (99 of 286) and 21.2% (25 of 118) among term and preterm children, respectively. Skin biomarkers collected at birth did not predict AD. Elevated thymus- and activation-regulated chemokine/C-C motif chemokine ligand 17 -levels collected at 2 months of age increased the overall risk of AD (HR: 2.11; 95% CI: 1.36-3.26; P = .0008) and moderate-to-severe AD (HR: 4.97; 95% CI: 2.09-11.80; P = .0003). IL-8 and IL-18 predicted moderate-to-severe AD. Low filaggrin degradation product levels increased the risk of AD (HR: 2.04; 95% CI: 1.32-3.15; P = .001). Elevated biomarker levels at 2 months predicted AD at other skin sites and many months after collection. CONCLUSIONS: This study showed that noninvasively collected skin biomarkers of barrier and immune pathways can precede the onset of AD.

Randomized double-blind placebo-controlled cosmetic trial of a topical first-in-class Neutraligand targeting the chemokine TARC/CCL17 in mild-to-moderate atopic dermatitis.

BACKGROUND: Atopic dermatitis has a marked economic impact and affects the quality of life. A cosmetic compound with an innovative strategy is proposed here as a small chemical neutraligand, GPN279 (previously identified as a theophylline derivative), that binds and potently neutralizes the TARC/CCL17 chemokine, activating the Th2 cell-expressed CCR4 receptor. OBJECTIVE: Our objective was to evaluate the safety and activity of topically applied GPN279 in mild-to-moderate atopic dermatitis patients in a randomized, double-blind, placebo-controlled, parallel group trial. Such cosmetic active ingredient targeting dry skin with an atopic tendency would open a parallel strategy to the pharmaceutical approach, in particular for mild to moderate subjects, as an alternative to reduce the evolution towards severe forms of atopy. METHODS: This 4-week trial included adults with mild-to-moderate atopic dermatitis, according to the SCORAD index. Patients were randomized into two groups treated by topical applications of either an emulsion containing 0.44% GPN279 in placebo on skin lesions or the placebo (4.56% glycerin). Clinical activity was evaluated with the SCORAD as the primary objective. As secondary objectives, POEM, erythema, skin moisturization, its barrier function (TEWL) and safety were evaluated. RESULTS: Twenty-one patients in each group completed the study. SCORAD was significantly improved in the GPN279 group vs. placebo. GPN279 also significantly improved POEM, induced a rapid and significant decrease of erythema, and improved skin moisture. GPN279 and placebo were well tolerated throughout the study. CONCLUSION: A cosmetic cream comprising the CCL17 neutraligand GPN279 improved the skin barrier and physiology criteria in patients with mild-to-moderate atopic dermatitis.

GÉNÉRALITÉS: La dermatite atopique a un impact économique marqué et affecte la qualité de vie. Un composé cosmétique dote d'une stratégie innovante est proposé ici sous la forme d'un petit neutraligand chimique, le GPN279 (précédemment identifié comme un dérivé de la théophylline), qui se lie et neutralise puissamment la chimiokine TARC/CCL17, activant le récepteur CCR4 exprimé par les cellules Th2. OBJECTIF: Notre objectif était d'évaluer l'innocuité et l'activité du GPN279 appliqué localement chez des patients atteints de dermatite atopique légère à modérée dans un essai randomisé, en double aveugle contre placebo et en groupes parallèles. Un tel actif cosmétique ciblant les peaux sèches à tendance atopique ouvrirait une stratégie parallèle à l'approche pharmaceutique, notamment pour les sujets atteints de forme légère à modérée, comme alternative visant à réduire l'évolution vers des formes sévères d'atopie. MÉTHODES: Cet essai de 4 semaines incluait des adultes atteints de dermatite atopique légère à modérée, selon l'indice SCORAD. Les patients ont été randomisés en deux groupes traités par application topique sur les lésions cutanées soit d'une émulsion contenant 0,44% de GPN279 dans un placebo, soit du placebo seul (4,56% de glycérine). L'activité clinique a été évaluée selon l'indice SCORAD comme objectif principal. Les objectifs secondaires évaluaient le POEM, l'érythème, l'hydratation de la peau, sa fonction barrière (TEWL) et la sécurité. RÉSULTATS: Vingt et un patients de chaque groupe ont terminé l'étude. L'indice SCORAD a été significativement amélioré dans le groupe GPN279 par rapport au placebo. Le GPN279 a également amélioré de manière significative le POEM, a induit une diminution rapide et significative de l'érythème et amélioré l'hydratation de la peau. Le GPN279 et le placebo ont été bien tolérés tout au long de l'étude. CONCLUSION: Une crème cosmétique contenant le neutraligand CCL17 GPN279 améliore la barrière cutanée et les critères physiologiques chez les patients atteints de dermatite atopique légère à modérée.

CCL17 Aggravates Myocardial Injury by Suppressing Recruitment of Regulatory T Cells.

BACKGROUND: Recent studies have established that CCR2 (C-C chemokine receptor type 2) marks proinflammatory subsets of monocytes, macrophages, and dendritic cells that contribute to adverse left ventricle (LV) remodeling and heart failure progression. Elucidation of the effector mechanisms that mediate adverse effects of CCR2+ monocytes, macrophages, and dendritic cells will yield important insights into therapeutic strategies to suppress myocardial inflammation. METHODS: We used mouse models of reperfused myocardial infarction, angiotensin II and phenylephrine infusion, and diphtheria toxin cardiomyocyte ablation to investigate CCL17 (C-C chemokine ligand 17). We used Ccl17 knockout mice, flow cytometry, RNA sequencing, biochemical assays, cell trafficking studies, and in vivo cell depletion to identify the cell types that generate CCL17, define signaling pathways that controlled its expression, delineate the functional importance of CCL17 in adverse LV remodeling and heart failure progression, and determine the mechanistic basis by which CCL17 exerts its effects. RESULTS: We demonstrated that CCL17 is expressed in CCR2+ macrophages and cluster of differentiation 11b+ conventional dendritic cells after myocardial infarction, angiotensin II and phenylephrine infusion, and diphtheria toxin cardiomyocyte ablation. We clarified the transcriptional signature of CCL17+ macrophages and dendritic cells and identified granulocyte-macrophage colony-stimulating factor (GM-CSF) signaling as a key regulator of CCL17 expression through cooperative activation of STAT5 (signal transducer and activator of transcription 5) and canonical NF-κB (nuclear factor κ-light-chain-enhancer of activated B cells) signaling. Ccl17 deletion resulted in reduced LV remodeling, decreased myocardial fibrosis and cardiomyocyte hypertrophy, and improved LV systolic function after myocardial infarction and angiotensin II and phenylephrine infusion. We observed increased abundance of regulatory T cells (Tregs) in the myocardium of injured Ccl17 knockout mice. CCL17 inhibited Treg recruitment through biased activation of CCR4. CCL17 activated Gq signaling and CCL22 (C-C chemokine ligand 22) activated both Gq and ARRB (ß-arrestin) signaling downstream of CCR4. CCL17 competitively inhibited CCL22 stimulated ARRB signaling and Treg migration. We provide evidence that Tregs mediated the protective effects of Ccl17 deletion on myocardial inflammation and adverse LV remodeling. CONCLUSIONS: These findings identify CCL17 as a proinflammatory mediator of CCR2+ macrophages and dendritic cells and suggest that inhibition of CCL17 may serve as an effective strategy to promote Treg recruitment and suppress myocardial inflammation.

Thymus and activation-regulated chemokine (TARC) as treatment response marker for paediatric Hodgkin lymphoma: A pilot study.

Classical Hodgkin lymphoma (cHL) is characterised by malignant Hodgkin Reed-Sternberg cells located in an inflammatory microenvironment. Blood biomarkers result from active cross-talk between malignant and non-malignant cells. One promising biomarker in adult patients with cHL is thymus and activation-regulated chemokine (TARC). We investigated TARC as marker for interim and end-of-treatment response in paediatric cHL. In this multicentre prospective study, TARC levels were measured among 99 paediatric patients with cHL before each cycle of chemotherapy and were linked with interim and end-of-treatment remission status. TARC levels were measured by enzyme-linked immunosorbent assay. At diagnosis, TARC levels were elevated in 96% of patients. Plasma TARC levels declined significantly after one cycle of chemotherapy (p < 0.01 vs. baseline) but did not differ at interim assessment by positron emission tomography (p = 0.31). In contrast, median plasma TARC at end of treatment was significantly higher in three patients with progressive disease compared to those in complete remission (1.226 vs. 90 pg/ml; p < 0.001). We demonstrate that, in paediatric patients, plasma TARC is a valuable response marker at end-of-treatment, but not at interim analysis after the first two chemotherapy cycles. Further research is necessary to investigate TARC as marker for long-term progression free survival.

CCL17/TARC in autoimmunity and inflammation-not just a T-cell chemokine.

Chemokine (C-C) ligand 17 (CCL17) was first identified as thymus- and activation-regulated chemokine when it was found to be constitutively expressed in the thymus and identified as a T-cell chemokine. This chemoattractant molecule has subsequently been found at elevated levels in a range of autoimmune and inflammatory diseases, as well as in cancer. CCL17 is a C-C chemokine receptor type 4 (CCR4) ligand, with chemokine (C-C) ligand 22 being the other major ligand and, as CCR4 is highly expressed on helper T cells, CCL17 can play a role in T-cell-driven diseases, usually considered to be via its chemotactic activity on T helper 2 cells; however, given that CCR4 is also expressed by other cell types and there is elevated expression of CCL17 in many diseases, a broader CCL17 biology is suggested. In this review, we summarize the biology of CCL17, its regulation and its potential contribution to the pathogenesis of various preclinical models. Reference is made, for example, to recent literature indicating a role for CCL17 in the control of pain as part of a granulocyte macrophage-colony-stimulating factor/CCL17 pathway in lymphocyte-independent models and thus not as a T-cell chemokine. The review also discusses the potential for CCL17 to be a biomarker and a therapeutic target in human disorders.

The GM-CSF/CCL17 pathway in obesity-associated osteoarthritic pain and disease in mice.

OBJECTIVES: We have previously identified a granulocyte macrophage-colony stimulating factor (GM-CSF)/C-C motif ligand 17 (CCL17) pathway in monocytes/macrophages, in which GM-CSF regulates the formation of CCL17, and it is important for an experimental osteoarthritis (OA) model. We explore here additional OA models, including in the presence of obesity, such as a requirement for this pathway. DESIGN: The roles of GM-CSF, CCL17, CCR4, and CCL22 in various experimental OA models, including those incorporating obesity (eight-week high-fat diet), were investigated using gene-deficient male mice. Pain-like behavior and arthritis were assessed by relative static weight distribution and histology, respectively. Cell populations (flow cytometry) and cytokine messenger RNA (mRNA) expression (qPCR) in knee infrapatellar fat pad were analyzed. Human OA sera were collected for circulating CCL17 levels (ELISA) and OA knee synovial tissue for gene expression (qPCR). RESULTS: We present evidence that: i) GM-CSF, CCL17, and CCR4, but not CCL22, are required for the development of pain-like behavior and optimal disease in three experimental OA models, as well as for exacerbated OA development due to obesity, ii) obesity alone leads to spontaneous knee joint damage in a GM-CSF- and CCL17-dependent manner, and iii) in knee OA patients, early indications are that BMI correlates with a lower Oxford Knee Score (r = -0.458 and p = 0.0096), with elevated circulating CCL17 levels (r = 0.2108 and p = 0.0153) and with elevated GM-CSF and CCL17 gene expression in OA synovial tissue. CONCLUSIONS: The above findings indicate that GM-CSF, CCL17, and CCR4 are involved in obesity-associated OA development, broadening their potential as targets for possible treatments for OA.

Skin biomarkers predict development of atopic dermatitis in infancy.

BACKGROUND: There is currently no insight into biomarkers that can predict the onset of pediatric atopic dermatitis (AD). METHODS: Nested in a prospective birth cohort study that examined the occurrence of physician-diagnosed AD in 300 children, 44 random children with onset of AD in the first year of life were matched on sex and season of birth with 44 children who did not develop AD. Natural moisturizing factor (NMF), corneocyte surface protrusions, cytokines, free sphingoid bases (SBs) of different chain lengths and their ceramides were analyzed from tape strips collected at 2 months of age before onset of AD using liquid chromatography, atomic force microscopy, multiplex immunoassay, and liquid chromatography mass spectrometry, respectively. RESULTS: Significant alterations were observed for four lipid markers, with phytosphingosine ([P]) levels being significantly lower in children who developed AD compared with children who did not (median 240 pmol/mg vs. 540 pmol/mg, p < 0.001). The two groups of children differed in the relative amounts of SB of different chain lengths (C17, C18 and C20). Thymus- and activation-regulated chemokine (TARC/CCL17) was slightly higher in children who developed AD, whereas NMF and corneocyte surface texture were similar. AD severity assessed by the eczema area and severity index (EASI) at disease onset was 4.2 (2.0;7.2). [P] had the highest prediction accuracy among the biomarkers (75.6%), whereas the combination of 5 lipid ratios gave an accuracy of 89.4%. CONCLUSION: This study showed that levels and SB chain length were altered in infants who later developed AD, and that TARC/CCL17 levels were higher.

Are blood cytokines reliable biomarkers of allergic disease diagnosis and treatment responses?

With the development of targeted therapies for allergic diseases, the need for biomarkers supporting disease diagnosis and management has increased. Recent research has elucidated the pattern of cytokines and their distinct roles in the pathogenesis of allergic diseases. This means that cytokines should be considered as biomarkers. In this review article, we summarize published findings and critically discuss the use of cytokine measurements in association with disease diagnosis and management. Among the variety of suggested cytokines, thymus and activation-regulated chemokine (TARC) stands out and can indeed serve as a biomarker of atopic dermatitis. Both biologic characteristics and technical issues determine the reliability and limit the use of blood cytokines as biomarkers.

Fulvic Acid Attenuates Atopic Dermatitis by Downregulating CCL17/22.

The main pathogenic factor in atopic dermatitis (AD) is Th2 inflammation, and levels of serum CCL17 and CCL22 are related to severity in AD patients. Fulvic acid (FA) is a kind of natural humic acid with anti-inflammatory, antibacterial, and immunomodulatory effects. Our experiments demonstrated the therapeutic effect of FA on AD mice and revealed some potential mechanisms. FA was shown to reduce TARC/CCL17 and MDC/CCL22 expression in HaCaT cells stimulated by TNF-α and IFN-γ. The inhibitors showed that FA inhibits CCL17 and CCL22 production by deactivating the p38 MAPK and JNK pathways. After 2,4-dinitrochlorobenzene (DNCB) induction in mice with atopic dermatitis, FA effectively reduced the symptoms and serum levels of CCL17 and CCL22. In conclusion, topical FA attenuated AD via downregulation of CCL17 and CCL22, via inhibition of P38 MAPK and JNK phosphorylation, and FA is a potential therapeutic agent for AD.