CXCL4 is a novel inducer of human Th17 cells and correlates with IL‐17 and IL‐22 in psoriatic arthritis

CXCL4 regulates multiple facets of the immune response and is highly upregulated in various Th17‐associated rheumatic diseases. However, whether CXCL4 plays a direct role in the induction of IL‐17 production by human CD4⁺ T cells is currently unclear. Here, we demonstrated that CXCL4 induced human CD4⁺ T cells to secrete IL‐17 that co‐expressed IFN‐γ and IL‐22, and differentiated naïve CD4⁺ T cells to become Th17‐cytokine producing cells. In a co‐culture system of human CD4⁺ T cells with monocytes or myeloid dendritic cells, CXCL4 induced IL‐17 production upon triggering by superantigen. Moreover, when monocyte‐derived dendritic cells were differentiated in the presence of CXCL4, they orchestrated increased levels of IL‐17, IFN‐γ, and proliferation by CD4⁺ T cells. Furthermore, the CXCL4 levels in synovial fluid from psoriatic arthritis patients strongly correlated with IL‐17 and IL‐22 levels. A similar response to CXCL4 of enhanced IL‐17 production by CD4⁺ T cells was also observed in patients with psoriatic arthritis. Altogether, we demonstrate that CXCL4 boosts pro‐inflammatory cytokine production especially IL‐17 by human CD4⁺ T cells, either by acting directly or indirectly via myeloid antigen presenting cells, implicating a role for CXCL4 in PsA pathology.     

IL‐17 Increased in the Third Trimester in Healthy Women with Term Labor

Citation Martínez‐García EA, Chávez‐Robles B, Sánchez‐Hernández PE, Nuñez‐Atahualpa L, Martín‐Máquez BT, Muñoz‐Gómez A, González‐López L, Gámez‐Nava JI, Salazar‐Páramo M, Dávalos‐Rodríguez I, Petri MH, Zuñiga‐Tamayo D, Vargas‐Ramírez R, Vázquez‐Del Mercado M. IL‐17 Increased in the third trimester in healthy women with term labor. Am J Reprod Immunol 2011; 65: 99–103 Introduction The function, peripheral blood expression, and physiologic importance of IL‐17 is not well established. Detection of IL‐17 in sera and plasma samples from patients with pre‐eclampsia has been reported with inconsistent results. To establish the l levels of the IL‐17 at peripheral level, we studied prospectively a cohort of 13 healthy pregnant women. Objective To evaluate the changes in serum levels of IL‐17 in healthy pregnant women in a prospective cohort. Material and Methods Thirteen healthy pregnant women were prospectively followed to evaluate serum levels of IL‐17. Each patient was evaluated at each trimester. IL‐17 levels were measured by ELISA. The statistical analysis was done using repeated measures anova and Bonferroni′s multiple comparison test. Results IL‐17 levels were significantly increased from first trimester with a mean of 14.61 up to 31.78 pg/mL at third trimester (P < 0.05), but when detectable, they were almost identical range in all trimesters. Conclusions We propose that IL‐17 levels in healthy women are present with very similar range levels during the whole pregnancy but the average is increased during the third trimester maybe as a part of the complex network of cytokines as a result of implantation, fetal development, and labor process itself.     

Committed Tc17 cells are phenotypically and functionally resistant to the effects of IL‐27

IL‐17‐secreting CD8⁺ T cells (Tc17 cells) have been implicated in immunity to infections, cancer, and autoimmune diseases. Thus far, studies on Tc17 cells have primarily investigated their development from naïve precursors, while the biology of committed Tc17 cells has been less characterized, in particular during the effector phase of immune responses. IL‐27 is an important regulator of inflammation through the induction of regulatory Tr1 cells, as well as a suppressor of Th17‐cell development. IL‐27 suppresses the development of Tc17 cells, but its effects on committed Tc17 cells are unknown. Here we demonstrate that even though IL‐27 completely inhibited the development of C57BL/6 mouse Tc17 cells, it had little effect on previously committed Tc17 cells. Although committed Tc17 cells were capable of responding to IL‐27, it had no effect on expression of RORγt and RORα, or production of various cytokines. Committed Tc17 cells did not express granzyme B and lacked cytotoxicity in vitro, features that remained unaltered by IL‐27 treatment. Nonetheless, they efficiently induced diabetes, irrespective of treatment with IL‐27 prior to transfer into RIP‐mOVA mice. These findings suggest that use of IL‐27 to modulate autoimmune diseases might have limited therapeutic efficacy if autoaggressive Tc17 cells have already developed.     

IL‐11 Expression in Human Term Placental Macrophages

Citation Pavlov OV, Kramareva NL, Selkov SA. IL‐11 Expression in human term placental macrophages. Am J Reprod Immunol 2011; 65: 397–402 Problem IL‐11 is a cytokine with pleiotropic activities, including gestational effects. Whereas IL‐11 production by maternal reproductive tissues is extensively studied, there is poor information about IL‐11 sources in the fetal counterpart of the maternal–fetal unit. Method of study We investigated the expression of IL‐11 in the purified human term placenta macrophages, using flow cytometry and immunoenzyme assay. Results Intracellular IL‐11 was detected in a substantial proportion of cultured CD68⁺ cells (median 38%). IL‐11 secretion by the placental macrophages was observed after 23‐hr cultivation (median 4.3 pg/10⁵ cells). Stimulation with lipopolysaccharide did not significantly change both intracellular expression and secretion of the cytokine. Conclusion Demonstrated IL‐11 expression by placental macrophages suggests that non‐trophoblast cells contribute to IL‐11 production at the maternal–fetal interface and thus account for the reproductive effects of the cytokine.     

Reciprocal expression of IL‐25 and IL‐17A is important for allergic airways hyperreactivity

Background Interleukin (IL)‐25 (IL‐17E) is a potent inducer of the type‐2 immune effector response. Previously we have demonstrated that a neutralizing anti‐IL‐25 antibody, given during the establishment of ovalbumin‐specific lung allergy, abrogates airways hyperreactivity. Objective Blocking IL‐25 results in the suppression of IL‐13, a cytokine known to exacerbate pulmonary inflammation, and an unexpected reciprocal increase in IL‐17A. The role of IL‐17A in asthma is complex with reports of both pro‐inflammatory and anti‐inflammatory functions. Our aim was to determine the influence of IL‐17A in regulating IL‐25‐dependent lung allergy. Method Neutralizing antibodies to IL‐25 and/or IL‐17A were administered during an experimental model of allergic asthma. Bronchoalveolar cell infiltrates and lung cytokine production were determined to assess lung inflammation. Invasive plethysmography was undertaken to measure lung function. Results Neutralization of IL‐25 correlated with a decrease in IL‐13 levels and an increase in IL‐17A production, and an accompanying prevention of airway hyperresponsiveness (AHR). Notably, the blocking of IL‐17A reversed the protective effects of treating with anti‐IL‐25 antibodies, resulting in the re‐expression of several facets of the lung inflammatory response, including IL‐13 and eotaxin production, eosinophilia and AHR. Using mice over‐expressing IL‐13 we demonstrate that treatment of these mice with anti‐IL‐25 fails to suppress IL‐13 levels and in turn IL‐17A levels remain suppressed. Conclusions and Clinical Relevance IL‐13 is known to be an important inducer of lung inflammation, causing goblet cell hyperplasia and promoting airways hyperreactivity. Our data now demonstrate that IL‐13 also plays an important role in the genesis of lung inflammation downstream of IL‐25 by suppressing a protective IL‐17A response. These findings also highlight the important reciprocal interplay of the IL‐17 family members, IL‐25 and IL‐17A, in regulating allergic lung responses and suggest that the balance of IL‐17A, together with IL‐25, will be an important consideration in the treatment of allergic asthma. Cite this as: J. L. Barlow, R. J. Flynn, S. J. Ballantyne and A. N. J. McKenzie, Clinical & Experimental Allergy, 2011 (41) 1447–1455.     

In-vivo study of diazepam transfer across the first trimester human placenta

Diazepam transfer by the first trimester human placenta wasinvestigated at pregnancy termination between 6 and 12 weeksof gestation. Fetal fluid samples were obtained from the exocoelomicand amniotic cavities of 65 pregnancies between 8 and 25 minfollowing the i.v. administration of 0.1 mg/kg diazepam to themother. Diazepam was detected in one-third of coelomic fluidsamples and two-thirds of amniotic fluid samples. Maternal serumand urine diazepam concentrations correlated negatively andpositively respectively, with time from drug injection to sampling.Individual diazepam concentrations were low on the fetal side,and the corresponding concentrations were independent of maternalserum concentrations and the time from drug injection to sampling.Amniotic fluid diazepam content increased significantly withadvancing gestational age. A multiple regression analysis showedthat the diazepam content of the coelomic fluid was not influencedby maternal serum diazepam concentration, the time from druginjection to sampling or gestational age, whereas only gestationalage contributed to the diazepam content of amniotic fluid. Thesedata demonstrate that the placental transfer of diazepam occursfrom week 6 of gestation, indicate a preferential transfer ofthis drug to the amniotic cavity and suggest that diazepam mayaccumulate in fetal circulation and tissues during organo-genesis.     

IL‐23 protection against Plasmodium berghei infection in mice is partially dependent on IL‐17 from macrophages

Although IL‐12 is believed to contribute to protective immune responses, the role played by IL‐23 (a member of the IL‐12 family) in malaria is elusive. Here, we show that IL‐23 is produced during infection with Plasmodium berghei NK65. Mice deficient in IL‐23 (p19KO) had higher parasitemia and died earlier than wild‐type (WT) controls. Interestingly, p19KO mice had lower numbers of IL‐17‐producing splenic cells than their WT counterparts. Furthermore, mice deficient in IL‐17 (17KO) suffered higher parasitemia than the WT controls, indicating that IL‐23‐mediated protection is dependent on induction of IL‐17 during infection. We found that macrophages were responsible for IL‐17 production in response to IL‐23. We observed a striking reduction in splenic macrophages in the p19KO and 17KO mice, both of which became highly susceptible to infection. Thus, IL‐17 appears to be crucial for maintenance of splenic macrophages. Adoptive transfer of macrophages into macrophage‐depleted mice confirmed that macrophage‐derived IL‐17 is required for macrophage accumulation and parasite eradication in the recipient mice. We also found that IL‐17 induces CCL2/7, which recruit macrophages. Our findings reveal a novel protective mechanism whereby IL‐23, IL‐17, and macrophages reduce the severity of infection with blood‐stage malaria parasites.     

IL‐22 modulates IL‐17A production and controls inflammation and tissue damage in experimental dengue infection

Dengue virus (DENV), a mosquito‐borne flavivirus, is a public health problem in many tropical countries. IL‐22 and IL‐17A are key cytokines in several infectious and inflammatory diseases. We have assessed the contribution of IL‐22 and IL‐17A in the pathogenesis of experimental dengue infection using a mouse‐adapted DENV serotype 2 strain (P23085) that causes a disease that resembles severe dengue in humans. We show that IL‐22 and IL‐17A are produced upon DENV‐2 infection in immune‐competent mice. Infected IL‐22^?/? mice had increased lethality, neutrophil accumulation and pro‐inflammatory cytokines in tissues, notably IL‐17A. Viral load was increased in spleen and liver of infected IL‐22^?/? mice. There was also more severe liver injury, as seen by increased transaminases levels and tissue histopathology. γδ T cells and NK cells are sources of IL‐17A and IL‐22, respectively, in liver and spleen. We also show that DENV‐infected HepG2 cells treated with rhIL‐22 had reduced cell death and decreased IL‐6 production. IL‐17RA^?/? mice were protected upon infection and IL‐17A‐neutralizing‐Ab‐treatment partially reversed the phenotype observed in IL‐22^?/?‐infected mice. We suggest that disrupting the balance between IL‐22 and IL‐17A levels may represent an important strategy to reduce inflammation and tissue injury associated with severe dengue infection.     

IL‐17 and anti‐bacterial immunity: Protection versus tissue damage

IL‐17 can impact health in a variety of ways. It is protective for some pathogens but it is also associated with tissue damaging inflammation. By examining the role of IL‐17 in a variety of bacterial infections the mechanisms by which this cytokine mediates both protection and damage can be dissected. A key element in understanding the role of this cytokine is determining where and when it is acting. Dissecting its essential protective role from its immunopathologic role will allow for improved intervention in both acute and chronic disease.     

IL‐23‐driven encephalo‐tropism and Th17 polarization during CNS‐inflammation in vivo

IL‐23 but not IL‐12 is essential for the development of autoimmune tissue inflammation in mice. Conversely, IL‐12 and IL‐23 impact on the polarization of Th1 and Th17 cells, respectively. While both polarized T helper populations can mediate autoimmune inflammation, their redundancy in the pathogenesis of EAE indicates that IL‐23 exerts its crucial influence on the disease independent of its T helper polarizing capacity. To study the impact of IL‐23 and IL‐12 on the behavior of encephalitogenic T cells in vivo, we generated BM‐chimeric mice in which we can trace individual populations of IL‐23 or IL‐12 responsive T helper cells during EAE. We observed that T cells, which lack IL‐12Rβ1 (no IL‐12 and IL‐23 signaling), fail to invade the CNS and do not acquire a Th17 phenotype. In contrast, loss of IL‐12 signaling prevents Th1 polarization but does not prevent T‐cell entry into the CNS. The loss of IL‐12R engagement does not appear to alter T‐cell expansion but leads to their accumulation in secondary lymphoid organs. We found that IL‐23 licenses T cells to invade the target tissue and to exert their effector function, whereas IL‐12 is critical for Th1 differentiation, but does not influence the pathogenic capacity of auto‐reactive T helper cells in vivo.     

Nasal IL‐17F is related to bronchial IL‐17F/neutrophilia and exacerbations in stable atopic severe asthma

Severe asthma (SA) is associated with neutrophil recruitment and T helper (T_H)17 chemokine overexpression in bronchial biopsies. We aimed to evaluate IL‐17A and IL‐17F expression in nasal/bronchial lamina propria of atopic mild‐to‐severe asthmatics and controls in relation to neutrophilia and asthma exacerbations. Cryostat sections of nasal/bronchial biopsies obtained from 14 SA and 14 mild asthma (MA) stable atopic patients with rhinitis, and seven healthy controls were analyzed by immunohistochemistry for neutrophils, IL‐17A and IL‐17F expression. Atopic SA showed an increase in asthma exacerbations number, IL‐17F and IL‐17A expression in nasal/bronchial lamina propria compared to MA and controls, and a higher expression of bronchial neutrophils in SA compared to MA and controls. In all asthmatics, significant relationships were found between bronchial IL‐17F and neutrophils/FEV₁, nasal IL‐17F and bronchial neutrophil/IL‐17 markers and between the latter and exacerbations, suggesting that nasal IL‐17F might be informative on bronchial IL17‐driven neutrophilia in atopic SA.     

Phosphorylated STAT3 and PD‐1 regulate IL‐17 production and IL‐23 receptor expression in Mycobacterium tuberculosis infection

We studied the factors that regulate IL‐23 receptor expression and IL‐17 production in human tuberculosis infection. Mycobacterium tuberculosis (M. tb)‐stimulated CD4⁺ T cells from tuberculosis patients secreted less IL‐17 than did CD4⁺ T cells from healthy tuberculin reactors (PPD⁺). M. tb‐cultured monocytes from tuberculosis patients and PPD⁺ donors expressed equal amounts of IL‐23p19 mRNA and protein, suggesting that reduced IL‐23 production is not responsible for decreased IL‐17 production by tuberculosis patients. Freshly isolated and M. tb‐stimulated CD4⁺ T cells from tuberculosis patients had reduced IL‐23 receptor and phosphorylated STAT3 (pSTAT3) expression, compared with cells from PPD⁺ donors. STAT3 siRNA reduced IL‐23 receptor expression and IL‐17 production by CD4⁺ T cells from PPD⁺ donors. Tuberculosis patients had increased numbers of PD‐1⁺ T cells compared with healthy PPD⁺ individuals. Anti‐PD‐1 antibody enhanced pSTAT3 and IL‐23R expression and IL‐17 production by M. tb‐cultured CD4⁺ T cells of tuberculosis patients. Anti‐tuberculosis therapy decreased PD‐1 expression, increased IL‐17 and IFN‐γ production and pSTAT3 and IL‐23R expression. These findings demonstrate that increased PD‐1 expression and decreased pSTAT3 expression reduce IL‐23 receptor expression and IL‐17 production by CD4⁺ T cells of tuberculosis patients.     

IL‐6: Regulator of Treg/Th17 balance

IL‐6 is a pleiotropic cytokine involved in the physiology of virtually every organ system. Recent studies have demonstrated that IL‐6 has a very important role in regulating the balance between IL‐17‐producing Th17 cells and regulatory T cells (Treg). The two T‐cell subsets play prominent roles in immune functions: Th17 cell is a key player in the pathogenesis of autoimmune diseases and protection against bacterial infections, while Treg functions to restrain excessive effector T‐cell responses. IL‐6 induces the development of Th17 cells from naïve T cells together with TGF‐β; in contrast, IL‐6 inhibits TGF‐β‐induced Treg differentiation. Dysregulation or overproduction of IL‐6 leads to autoimmune diseases such as multiple sclerosis (MS) and rheumatoid arthritis (RA), in which Th17 cells are considered to be the primary cause of pathology. Given the critical role of IL‐6 in altering the balance between Treg and Th17 cells, controlling IL‐6 activities is potentially an effective approach in the treatment of various autoimmune and inflammatory diseases. Here, we review the role of IL‐6 in regulating Th17/Treg balance and describe the critical functions of IL‐6 and Th17 in immunity and immune‐pathology.