Cooperation of interleukin-17 and interferon-gamma on chemokine secretion in human fetal intestinal epithelial cells

Human milk oligosaccharide disialyllacto-n-tetraose protects human intestinal epithelium integrity and permeability against mast cell chymase-induced disruption by stabilizing ZO-1/FAK/P38 pathway of intestinal epithelial cell

CONTEXT

Inflammatory bowel disease (IBD) is a chronic gut disease with intestinal-epithelium disruption. Mast cell (MC) has been discussed in IBD studies, but its subset MC_TC (chymase/tryptase) and MC-chymase have not been well-explored extensively. Human-milk-oligosaccharide-Disialyllacto-N-Tetraose (DSLNT) was reported as an effective strategy to protect infants against IBD with unclear mechanism.

OBJECTIVE

This study was to examine the distribution of chymase-positive mast cells in the intestinal-epithelium-tissue of IBD infants, to explore the MC-chymase function on intestinal-epithelium, and to investigate the influences of DSLNT against MC-chymase-induced disruptions.

MATERIALS AND METHODS

The intestinal-biopsies (surgical-waste) of the infants with IBD or with intestinal-atresia (non-IBD) were paraffin-embedded for immunohistochemistry. In-situ intestinal-tissue model and in-vitro human-intestinal-epithelial-cell (Caco-2) model were established with or without the treatments of MC-chymase (50mU/mL), DSLNT (600 µM) and DSLNT + MC-chymase respectively. The tissue morphology analysis, cell proliferation assay, cell-gap-closure assessment, fluorescence-immunocytochemistry, western blot, trans-epithelial-electrical-resistance, cell-cycle and statistical analysis were applied.

RESULTS

There was an increased number of MC_TC subset around the inflamed intestinal area in-vivo; MC-chymase caused intestinal-epithelial-barrier damage in-situ, decreased trans-epithelial-electrical-resistance of caco-2 cell monolayer in-vitro; while DSLNT protected epithelium against MC-chymase induced disruptions. MC-chymase reduced cell-viability, proliferation and migration, altered cell-cycle, down-regulated ZO-1, FAK, and P38 expressions, while DSLNT protected cells by impairing MC-chymase-induced interruptions. DSLNT can rescue ZO-1, FAK and P38 expressions and restore epithelial-cell integrity and cell cycle.

CONCLUSIONS

Chymase-positive MCs are involved in IBD progress. MC-chymase disrupts intracellular ZO-1/FAK/P38 signal pathway and cell-cell/cell-matrix contacts, while DSLNT protects intestinal-epithelium against MC-chymase to maintain the intestinal epithelium integrity.

The Roles of IL-17, IL-21, and IL-23 in the Helicobacter pylori Infection and Gastrointestinal Inflammation: A Review

Although millions of people have been infected by Helicobacter pylori (H. pylori), only a small proportion of infected individuals will develop adverse outcomes, ranging from chronic gastritis to gastric cancer. Advanced development of the disease has been well-linked with chronic inflammation, which is significantly impacted by the adaptive and humoral immunity response. From the perspective of cellular immunity, this review aims to clarify the intricate axis between IL-17, IL-21, and IL-23 in H. pylori-related diseases and the pathogenesis of inflammatory gastrointestinal diseases. CD4⁺ helper T (Th)-17 cells, with the hallmark pleiotropic cytokine IL-17, can affect antimicrobial activity and the pathogenic immune response in the gut environment. These circumstances cannot be separated, as the existence of affiliated cytokines, including IL-21 and IL-23, help maintain Th17 and accommodate humoral immune cells. Comprehensive understanding of the dynamic interaction between molecular host responses in H. pylori-related diseases and the inflammation process may facilitate further development of immune-based therapy.

IFN-γ and IL-17A regulate intestinal crypt production of CXCL10 in the healthy and inflamed colon

During intestinal inflammation, immature cells within the intestinal crypt are called upon to replenish lost epithelial cell populations, promote tissue regeneration, and restore barrier integrity. Inflammatory mediators including T_H1/T_H17-associated cytokines influence tissue health and regenerative processes, yet how these cytokines directly influence the colon crypt epithelium and whether the crypt remains responsive to these cytokines during active damage and repair, remain unclear. Here, using laser-capture microdissection and primary colon organoid culture, we show that the cytokine milieu regulates the ability of the colonic crypt epithelium to participate in proinflammatory signaling. IFN-γ induces the T_H1-recruiting, proinflammatory chemokine CXCL10/IP10 in primary murine intestinal crypt epithelium. CXCL10 was also induced in colonic organoids derived from mice with active, experimentally induced colitis, suggesting that the crypt can actively secrete CXCL10 in select cytokine environments during colitis. Colon expression of cxcl10 further increased during infectious and noninfectious colitis in Il17a^-/- mice, demonstrating that IL-17A exerts a negative effect on CXCL10 in vivo. Furthermore, IL-17A directly antagonized CXCL10 production in ex vivo organoid cultures derived from healthy murine colons. Interestingly, direct antagonism of CXCL10 was not observed in organoids derived from colitic mouse colons bearing active lesions. These data, highlighting the complex interplay between the cytokine milieu and crypt epithelia, demonstrate proinflammatory chemokines can be induced within the colonic crypt and suggest the crypt remains responsive to cytokine modulation during inflammation.NEW & NOTEWORTHY Upon damage, the intestinal epithelium regenerates to restore barrier function. Here we observe that the local colonic cytokine milieu controls the production of procolitic chemokines within the crypt base and colon crypts remain responsive to cytokines during inflammation. IFN-γ promotes, while IL-17 antagonizes, CXCL10 production in healthy colonic crypts, while responses to cytokines differ in inflamed colon epithelium. These data reveal novel insight into colon crypt responses and inflammation-relevant alterations in signaling.

Regulation of IL-17 in autoimmune diseases by transcriptional factors and microRNAs

In recent years, IL-17A (IL-17), a pro-inflammatory cytokine, has received intense attention of researchers and clinicians alike with documented effects in inflammation and autoimmune diseases. IL-17 mobilizes, recruits and activates different cells to increase inflammation. Although protective in infections, overproduction of IL-17 promotes inflammation in autoimmune diseases such as multiple sclerosis, rheumatoid arthritis, psoriasis, among others. Regulating IL-17 levels or action by using IL-17-blocking antibodies or IL-17R antagonist has shown to attenuate experimental autoimmune diseases. It is now known that in addition to IL-17-specific transcription factor, RORγt, several other transcription factors and select microRNAs (miRNA) regulate IL-17. Given that miRNAs are dysregulated in autoimmune diseases, a better understanding of transcriptional factors and miRNA regulation of IL-17 expression and function will be essential for devising potential new therapies. In this review, we will overview IL-17 induction and function in relation to autoimmune diseases. In addition, current findings on transcriptional regulation of IL-17 induction and plausible interplay between IL-17 and miRNA in autoimmune diseases are highlighted.

Investigating the contribution of IL-17A and IL-17F to the host response during Escherichia coli mastitis

Mastitis remains a major disease of cattle with a strong impact on the dairy industry. There is a growing interest in understanding how cell mediated immunity contributes to the defence of the mammary gland against invading mastitis causing bacteria. Cytokines belonging to the IL-17 family, and the cells that produce them, have been described as important modulators of the innate immunity, in particular that of epithelial cells. We report here that expression of IL-17A and IL-17F genes, encoding two members of the IL-17 family, are induced in udder tissues of cows experimentally infected with Escherichia coli. The impact of IL-17A on the innate response of bovine mammary epithelial cells was investigated using a newly isolated cell line, the PS cell line. We first showed that PS cells, similar to primary bovine mammary epithelial cells, were able to respond to agonists of TLR2 and to LPS, provided CD14 was added to the culture medium. We then showed that secretion of CXCL8 and transcription of innate immunity related-genes by PS cells were increased by IL-17A, in particular when these cells were stimulated with live E. coli bacteria. Together with data from the literature, these results support the hypothesis that IL-17A and IL-17 F could play an important role in mediating of host-pathogen interactions during mastitis.

Changes of cytokine levels in a mouse model of post-infectious irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a highly prevalent functional gastrointestinal disorder. Post-infectious IBS (PI-IBS) is caused by an acute gastrointestinal infection preceding the onset of symptoms. However, the pathophysiology of PI-IBS is not clear, and the purpose of this study was to investigate the probable immune mechanisms of PI-IBS.

METHODS

C57BL/6 mice were randomly assigned to either an infection group or a control group. Mice in the infection group were infected with Trichinella spiralis to establish a model of PI-IBS (500 Trichinella), while control mice received only salt solution. Visceral sensitivity of colorectal distention in mice was evaluated by abdominal withdrawal reflex scores and intestinal inflammation was assessed using hematoxylin-eosin staining; at day 56 post-infection, the mRNA and protein levels of specific cytokines in the gut segments were detected using reverse-transcription polymerase chain reaction and enzyme-linked immunoabsorbent assay.

RESULTS

Levels of interferon γ and interleukin (IL)-17 in the PI-IBS group were significantly increased in the duodenum and ileum, and IL-10 was decreased in the jejunum, ileum, and colon compared with control mice. However, the expression level of IL-1β was not significantly different between the two groups.

CONCLUSIONS

The present study suggests that the local low-grade inflammation and immune activation that are an important component of the pathophysiology of PI-IBS are primarily induced and maintained by specific cytokines.

IL-17A alone weakly affects the transcriptome of intestinal epithelial cells but strongly modulates the TNF-α-induced expression of inflammatory mediators and inflammatory bowel disease susceptibility genes

BACKGROUND

In contrast to anti-TNF-α antibodies, anti-IL-17A antibodies lacked clinical efficacy in a trial with patients suffering from Crohn's disease. We therefore analyzed how IL-17A modulates the inflammatory response elicited by TNF-α in intestinal epithelial cells (IEC).

METHODS

Target mRNA levels in IEC and colonic biopsies were assessed by RNA microarray and quantitative real-time PCR. Signaling pathways were analyzed using receptor neutralization and pharmacological inhibitors. Target protein levels were determined by immunoblotting.

RESULTS

Microarray analysis demonstrated that IL-17A alone is a weak inducer of gene expression in IEC (29 regulated transcripts), but significantly affected the TNF-α-induced expression of 547 genes, with strong amplification of proinflammatory chemokines and cytokines (>200-fold increase of CCL20, CXCL1, and CXCL8). Interestingly, IL-17A differentially modulated the TNF-α-induced expression of several inflammatory bowel disease susceptibility genes in IEC (increase of JAK2 mRNA, decrease of FUT2, ICAM1, and LTB mRNA). Negative regulation of ICAM-1 by IL-17A was verified on protein level. The significance of these findings is emphasized by inflamed lesions of patients with inflammatory bowel disease demonstrating significant correlations (P < 0.01, Rho, 0.57-0.85) for JAK2, ICAM1, and LTB mRNA with IL17A and TNF mRNA.

CONCLUSIONS

Our study demonstrates the modulation of inflammatory bowel disease susceptibility gene mRNA in IEC as a novel important property of IL-17A. Given the weak impact of sole IL-17A stimulation on IEC target gene expression, our study provides an important explanation for the lack of clinical efficacy of sole IL-17A neutralization, but suggests a beneficial effect of combined IL-17A/TNF-α that is currently in clinical development.

IL-17A potentiates TNFα-induced secretion from human endothelial cells and alters barrier functions controlling neutrophils rights of passage

Interleukin-17A (IL-17A) is an important pro-inflammatory cytokine that regulates leukocyte mobilization and recruitment. To better understand how IL-17A controls leukocyte trafficking across capillaries in the peripheral blood circulation, we used primary human dermal microvascular endothelial cells (HDMEC) to investigate their secretory potential and barrier function when activated with IL-17A and TNFα. Activation by TNFα and IL-17A causes phosphorylation of p38 as well as IκBα whereby NFκB subsequently becomes phosphorylated, a mechanism that initiates transcription of adhesion molecules such as E-selectin. Members of the neutrophil-specific GRO-family chemokines were significantly up-regulated upon IL-17A stimulation on the mRNA and protein level, whereas all tested non-neutrophil-specific chemokines remained unchanged in comparison. Moreover, a striking synergistic effect in the induction of granulocyte colony-stimulating factors (G-CSF) was elicited when IL-17A was used in combination with TNFα, and IL-17A was able to significantly augment the levels of TNFα-induced E-selectin and ICAM-1. In accordance with this observation, IL-17A was able to markedly increase TNFα-induced neutrophil adherence to HDMEC monolayers in an in vitro adhesion assay. Using a trans-well migration assay with an HDMEC monolayer as a barrier, we here show that pre-stimulating the endothelial cells with TNFα and IL-17A together enhances the rate of neutrophil transmigration compared to TNFα or IL-17A alone. These results show that IL-17A and TNFα act in cooperation to facilitate neutrophil migration across the endothelial cell barrier. In addition, the synergistic actions of IL-17A with TNFα to secrete G-CSF appear to be important for mobilizing neutrophils from the bone marrow to the blood stream.

The ex vivo production of IL-6 and IL-21 by CD4+ T cells is directly associated with neurological disability in neuromyelitis optica patients

Neuromyelitis optica (NMO), also known as Devic's disease, is an autoimmune, inflammatory disorder of the central nervous system (CNS) in which the immune system attacks myelin of the neurons located at the optic nerves and spinal cord, thus producing a simultaneous or sequential optic neuritis and myelitis. The objective of this study was evaluated the background T-cell function of patients suffering from neuromyelitis optica (NMO), an autoimmune disorder of the central nervous system. In our study, the in vitro T cell proliferation and the production of Th1 cytokines were significantly lower in cell cultures from NMO patients, as compared with healthy individuals. In contrast, a dominant Th17-like phenotype, associate with higher IL-23 and IL-6 production by LPS-activated monocytes, was observed among NMO patients. The release of IL-21 and IL-6 by polyclonally activated CD4+ T cells was directly correlated to neurological disability. In addition, the in vitro release of IL-21, IL-6 and IL-17 was significantly more resistant to glucocorticoid inhibition in NMO patients. In conclusion, the results indicate dominant Th17-related response in NMO patients that was directly proportional to neurological disability. Furthermore, our results can help to explain why NMO patients trend to be more refractory to corticoid treatment.

Endogenous interleukin-10 constrains Th17 cells in patients with inflammatory bowel disease

Background

Th17 cells play a role in inflammation. Interleukin (IL)-10 is a potent anti-inflammatory cytokine. However, it is poorly understood whether and how endogenous IL-10 impacts the development of Th17 cells in human pathologies.

Materials and methods

We examined the relationship between IL-10 and Th17 cells in patients with Crohn's disease and in IL-10-deficient (IL-10^-/-) mice. Th17 cells and dendritic cells (DCs) were defined by flow cytometry and evaluated by functional studies.

Results

We detected elevated levels of IL-17 and Th17 cells in the intestinal mucosa of patients with Crohn's disease. Intestinal DCs from Crohn's patients produced more IL-1β than controls and were superior to blood DCs in Th17 induction through an IL-1-dependent mechanism. Furthermore, IL-17 levels were negatively associated with those of IL-10 and were positively associated those of IL-1β in intestinal mucosa. These data point toward an in vivo cellular and molecular link among endogenous IL-10, IL-1, and Th17 cells in patients with Crohn's disease. We further investigated this relationship in IL-10^-/- mice. We observed a systemic increase in Th17 cells in IL-10^-/- mice when compared to wild-type mice. Similar to the intestinal DCs in patients with Crohn's disease, murine IL-10^-/- DCs produced more IL-1β than their wild-type counterparts and promoted Th17 cell development in an IL-1-dependent manner. Finally, in vivo blockade of IL-1 receptor signaling reduced Th17 cell accumulation and inflammation in a mouse model of chemically-induced colitis.

Conclusions

Endogenous IL-10 constrains Th17 cell development through the control of IL-1 production by DCs, and reaffirms the crucial anti-inflammatory role of IL-10 in patients with chronic inflammation.

Expression of Th-17 and RORγt mRNA in Behçet's Disease

BACKGROUND

To investigate plasma IL-17 level and the expression of Th17 cell transcription factor RORγt in the pathogenesis of Behçet's Disease (BD).

MATERIAL/METHODS

Blood samples were collected from 73 patients with BD (45 patients were in active stage), 20 systemic lupus erythematosus (SLE) and 12 multiple sclerosis patients (MS). Twelve patients with BD were investigated both in their active and remission stages. Samples were processed to detect IL-17A level in plasma by enzyme-linked immunosorbent assay (ELISA). Related gene expression was assessed by real-time reverse transcription polymerase chain reaction. Function of Th17 cells in active BD patients with erythema nodosum (EN)-like eruption was studied in relation to human umbilical vein endothelial cells (HUVECs).

RESULTS

We demonstrated the presence of Th17 cells and RORγt among the peripheral blood mononuclear cells (PBMC). The percentage of circulating Th17 cells and the ability to produce interleukin-17A (IL-17A) were increased in samples derived from patients with active BD, MS and SLE patients. We observed that IL-17A from patients with active BD could induce adhesion molecule messenger RNA expression in HUVECs.

CONCLUSIONS

RORγt determined Th17 cell might be involved with increased IL-17A in BD. Our results indicate that IL-17 contributes to the active proinflammatory pattern that is characteristic of inflammatory diseases and patients with active BD.

Interleukin-17A differentially modulates BCG induction of cytokine production in human blood macrophages

The pathogenesis of Mtb depends in part on cytokine cross-regulation between macrophages and T cells in host immunity. Th17 cells produce IL-17A to induce granuloma formation and to restrict mycobacterial dissemination. IL-17A also mediates cytokine responses induced by proinflammatory cytokines such as TNF-α. Our previous results showed that BCG induces IL-6, IL-10, and TNF-α via activity of protein kinases, including dsRNA-activated serine/threonine protein kinase and glycogen synthase kinase-3 in primary human monocytes. Therefore, we investigated whether IL-17A, upon its induction by BCG, plays an additional role to aid the production of downstream proinflammatory cytokines in macrophages. Here, we showed that IL-17A enhanced IL-6 mRNA and protein levels inducible by BCG in a time- and dose-dependent manner, whereas it had no effect on IL-10 and TNF-α production. We also demonstrated that IL-17A activated the phosphorylation of ERK1/2 triggered by BCG. With the use of a specific chemical inhibitor of a MAPK/ERK-activating kinase (MEK1/2), we confirmed the correlation between the enhanced ERK1/2 activation and augmented IL-6 production. Additionally, we revealed that IL-17A acts in concert with BCG-induced TNF-α to enhance the level of IL-6 synthesis. Taken together, our results suggest a significant role of IL-17A to serve as a modulator of cytokine expression in innate immune response during mycobacterial infection.

IL-17A induces CCL28, supporting the chemotaxis of IgE-secreting B cells

BACKGROUND

Atopic asthma is an allergic disease typically associated with T(H)2 cytokines. IL-17A is also associated with asthma, through the induction of chemokines. Mucosal CCL28 concentrations correlate with cellular recruitment to inflamed airways and support migration of IgA(+) B cells. Here, a link between IL-17A, CCL28 and IgE-secreting B cell chemotaxis is examined.

METHODS

Primary human airway cells and the airway epithelial line A549 were used to characterize IL-17A receptor expression and the effect of IL-17A on CCL28 transcription and translation. B cells, differentiated to IgE+ cells ex vivo, were assessed for CCR10 surface expression and chemotaxis to CCL28 by flow cytometry, transwell migration and ELISpot.

RESULTS

Human airway epithelium expressed both IL-17RA and IL-17RC, and was responsive to IL-17A stimulation. Cultured human IgE+ B cells expressed surface CCR10 and displayed CCR10-dependent chemotaxis towards recombinant CCL28. Enhanced levels of CCL28 were observed upon A549 cell incubation with IL-17A, and this up-regulation significantly increased the migration of IgE+ antibody-secreting B cells. The specificity of chemotaxis was confirmed by migration blockade in the presence of anti-CCL28 or anti-CCR10.

CONCLUSIONS

This work identifies a novel chemokine for the migration of IgE+ B cells, in addition to characterizing induction of CCL28 by IL-17A. Taken together the results presented here propose a new role for IL-17A in the allergic airways, linking this cytokine with the recruitment of IgE+ antibody-secreting B cells, via the induction of CCL28. These observations justify further in vivo studies of larger cohorts.

IL-17+ regulatory T cells in the microenvironments of chronic inflammation and cancer

Foxp3(+)CD4(+) regulatory T (Treg) cells inhibit immune responses and temper inflammation. IL-17(+)CD4(+) T (Th17) cells mediate inflammation of autoimmune diseases. A small population of IL-17(+)Foxp3(+)CD4(+) T cells has been observed in peripheral blood in healthy human beings. However, the biology of IL-17(+)Foxp3(+)CD4(+) T cells remains poorly understood in humans. We investigated their phenotype, cytokine profile, generation, and pathological relevance in patients with ulcerative colitis. We observed that high levels of IL-17(+)Foxp3(+)CD4(+) T cells were selectively accumulated in the colitic microenvironment and associated colon carcinoma. The phenotype and cytokine profile of IL-17(+)Foxp3(+)CD4(+) T cells was overlapping with Th17 and Treg cells. Myeloid APCs, IL-2, and TGF-β are essential for their induction from memory CCR6(+) T cells or Treg cells. IL-17(+)Foxp3(+)CD4(+) T cells functionally suppressed T cell activation and stimulated inflammatory cytokine production in the colitic tissues. Our data indicate that IL-17(+)Foxp3(+) cells may be "inflammatory" Treg cells in the pathological microenvironments. These cells may contribute to the pathogenesis of ulcerative colitis through inducing inflammatory cytokines and inhibiting local T cell immunity, and in turn may mechanistically link human chronic inflammation to tumor development. Our data therefore challenge commonly held beliefs of the anti-inflammatory role of Treg cells and suggest a more complex Treg cell biology, at least in the context of human chronic inflammation and associated carcinoma.

Substance P enhances Th17 phenotype in individuals with generalized anxiety disorder: an event resistant to glucocorticoid inhibition

Our objective was to evaluate the effect of stress-related dose of substance P (SP) on the in vitro proliferation and cytokine production in polyclonally activated T cells from healthy individuals or individuals with generalized anxiety disorder (GAD). Our results demonstrated that cell cultures from GAD group proliferated less following T cell activation, as compared with control group. The addition of SP enhanced, while the glucocorticoid (GC) reduced, the proliferative response in activated cell cultures from healthy but not from GAD individuals. The cytokine profile in GAD individuals revealed Th1 and Th2 deficiencies were associated with dominate Th17 phenotype which was enhanced by SP. Differently from control, the production of Th17 cytokines in GAD individuals was not affected by GC. In conclusion, our results show that complex T cell functional dysregulation in GAD individuals is significantly amplified by SP. These immune abnormalities can have impact in increasing the susceptibility to infectious diseases and inflammatory/autoimmune disorders in anxious individuals.

Bleomycin and IL-1beta-mediated pulmonary fibrosis is IL-17A dependent

Idiopathic pulmonary fibrosis (IPF) is a destructive inflammatory disease with limited therapeutic options. To better understand the inflammatory responses that precede and concur with collagen deposition, we used three models of pulmonary fibrosis and identify a critical mechanistic role for IL-17A. After exposure to bleomycin (BLM), but not Schistosoma mansoni eggs, IL-17A produced by CD4⁺ and γδ⁺ T cells induced significant neutrophilia and pulmonary fibrosis. Studies conducted with C57BL/6 il17a^−/− mice confirmed an essential role for IL-17A. Mechanistically, using ifnγ^−/−, il10^−/−, il10^−/−il12p40^−/−, and il10^−/−il17a^−/− mice and TGF-β blockade, we demonstrate that IL-17A–driven fibrosis is suppressed by IL-10 and facilitated by IFN-γ and IL-12/23p40. BLM-induced IL-17A production was also TGF-β dependent, and recombinant IL-17A–mediated fibrosis required TGF-β, suggesting cooperative roles for IL-17A and TGF-β in the development of fibrosis. Finally, we show that fibrosis induced by IL-1β, which mimics BLM-induced fibrosis, is also highly dependent on IL-17A. IL-17A and IL-1β were also increased in the bronchoalveolar lavage fluid of patients with IPF. Together, these studies identify a critical role for IL-17A in fibrosis, illustrating the potential utility of targeting IL-17A in the treatment of drug and inflammation-induced fibrosis.

IL-17 produced by neutrophils regulates IFN-gamma-mediated neutrophil migration in mouse kidney ischemia-reperfusion injury

The IL-23/IL-17 and IL-12/IFN-gamma cytokine pathways have a role in chronic autoimmunity, which is considered mainly a dysfunction of adaptive immunity. The extent to which they contribute to innate immunity is, however, unknown. We used a mouse model of acute kidney ischemia-reperfusion injury (IRI) to test the hypothesis that early production of IL-23 and IL-12 following IRI activates downstream IL-17 and IFN-gamma signaling pathways and promotes kidney inflammation. Deficiency in IL-23, IL-17A, or IL-17 receptor (IL-17R) and mAb neutralization of CXCR2, the p19 subunit of IL-23, or IL-17A attenuated neutrophil infiltration in acute kidney IRI in mice. We further demonstrate that IL-17A produced by GR-1+ neutrophils was critical for kidney IRI in mice. Activation of the IL-12/IFN-gamma pathway and NKT cells by administering alpha-galactosylceramide-primed bone marrow-derived DCs increased IFN-gamma production following moderate IRI in WT mice but did not exacerbate injury or enhance IFN-gamma production in either Il17a-/- or Il17r-/- mice, which suggested that IL-17 signaling was proximal to IFN-gamma signaling. This was confirmed by the finding that IFN-gamma administration reversed the protection seen in Il17a-/- mice subjected to IRI, whereas IL-17A failed to reverse protection in Ifng-/- mice. These results demonstrate that the innate immune component of kidney IRI requires dual activation of the IL-12/IFN-gamma and IL-23/IL-17 signaling pathways and that neutrophil production of IL-17A is upstream of IL-12/IFN-gamma. These mechanisms might contribute to reperfusion injury in other organs.

CD4 T-cell differentiation and inflammatory bowel disease

Differentiation of naïve T cells leads to the generation of T-cell subsets, each possessing distinct cytokine expression profiles for serving different immune functions. Through the activation of separate signaling pathways, this process results in both differentiated helper T (Th) cells, termed Th1, Th2 and Th17, and induced regulatory T cells, which suppress Th cells. These different cells are important for combating infectious diseases and cancers; however, when aberrant, they can be responsible for chronic inflammatory diseases. One such disease is inflammatory bowel disease (IBD), in which each T-cell subset can have a role in disease. New studies highlight the importance of the recently identified Th17 subset in IBD. Therapeutics targeting these aberrant Th responses are already under development and hold promise for treating IBD and other chronic inflammatory diseases.

Effects of IL-17 on human gingival fibroblasts

Interleukin (IL)-17 is present in inflammatory periodontal lesions, thus suggesting a role in mediating inflammation. We tested the hypothesis that IL-17, especially when combined with interferon (IFN)-gamma, may modulate the responses of human gingival fibroblasts (HGFs). IL-17 induced IL-8 and minimal intercellular adhesion molecule (ICAM)-1 expression. It had no effect on expression of HLA-DR, CD40, or the immune-suppressive enzyme indoleamine 2,3-dioxygenase (IDO). The effects of IL-17 on HGFs were compared with those of IFN-gamma. Unlike IL-17, IFN-gamma augmented the expression of HLA-DR, ICAM-1, and IDO, but not IL-8. Thus, IL-17 and IFN-gamma induce different HGF responses when administered separately. Interestingly, when IL-17 and IFN-gamma were combined, marked enhancement of ICAM-1, IL-8, and IDO expression by HGFs was observed. These findings suggest that IL-17, especially when combined with IFN-gamma, could play an important role in immune modulation through stimulation of HGFs in periodontal disease.

IFN-gamma is the only anti-rotavirus cytokine found after in vitro stimulation of memory CD4+ T cells from mice immunized with a chimeric VP6 protein

CD4+ T cells are the only lymphocytes required for protection of mice against rotavirus shedding after mucosal immunization with chimeric VP6 (MBP::VP6) and the adjuvant LT(R192G). One possible effector of protection is CD4+ T-cell cytokines. To determine if memory CD4+ T cells of immunized mice produce cytokines with direct anti-rotavirus activity, an in vitro infection model was developed using mouse CMT-93 cells and rhesus rotavirus (RRV). Spleen and lamina propria (LP) cells, as well as purified splenic CD4T cells obtained after intranasal immunization of BALB/c mice with MBP::VP6/LT(R192G) released large quantities of two cytokines (IL-17 and IFN-gamma) into cell supernatants when stimulated with MBP::VP6. Production of these same cytokines is rapidly upregulated in intestinal lymphocytes after rotavirus inoculation of immunized mice. IL-17 pretreatment of CMT-93 cells had no effect on subsequent RRV replication, but IFN-gamma was the most potent inhibitor within a panel of nine cytokines tested. Supernatants obtained after in vitro stimulation of splenic CD4+ T cells of immunized mice had high levels of anti-RRV activity and their pretreatment with mAb against IFN-gamma caused essentially complete loss of activity. Thus, IFN-gamma was the only cytokine identified in stimulated CD4+ T cells from immunized mice that directly inhibited rotavirus replication.

Structure-function relationships in the IL-17 receptor: implications for signal transduction and therapy

IL-17 is the defining cytokine of a newly-described "Th17" population that plays critical roles in mediating inflammation and autoimmunity. The IL-17/IL-17 receptor superfamily is the most recent class of cytokines and receptors to be described, and until recently very little was known about its function or molecular biology. However, in the last year important new insights into the composition and dynamics of the receptor complex and mechanisms of downstream signal transduction have been made, which will be reviewed here.

TH17 cells in the big picture of immunology

The pathogenesis of chronic inflammatory diseases is assumed to depend on activated T cells interacting with resident tissue cells or migratory inflammatory cells. The discovery of new T-cell subsets such as the IL-17-producing T(H)17 and T-regulatory cells innovated our understanding of T-cell biology. Studies on new subsets confirm the important role of T cells in the instruction of tissue cells and also demonstrate the important role of feedback regulation for the polarization toward distinct T-cell subsets. The understanding of IL-17 and T(H)17 differentiation pathways has also changed the perspective of immunologists regarding the basis of chronic tissue inflammation, particularly where T(H)1 cells were considered as driving force of the pathology. This review summarizes the recent developments on T(H) cell subsets and integrates these findings into existing concepts of immunopathologic mechanisms.

Association of gamma interferon and interleukin-17 production in intestinal CD4+ T cells with protection against rotavirus shedding in mice intranasally immunized with VP6 and the adjuvant LT(R192G)

Mucosal immunization of mice with chimeric, Escherichia coli-expressed VP6, the protein that comprises the intermediate capsid layer of the rotavirus particle, together with attenuated E. coli heat-labile toxin LT(R192G) as an adjuvant, reduces fecal shedding of rotavirus antigen by >95% after murine rotavirus challenge, and the only lymphocytes required for protection are CD4+ T cells. Because these cells produce cytokines with antiviral properties, the cytokines whose expression is upregulated in intestinal memory CD4+ T cells immediately after rotavirus challenge of VP6/LT(R192G)-immunized mice may be directly or indirectly responsible for the rapid suppression of rotavirus shedding. This study was designed to identify which cytokines are significantly upregulated in intestinal effector sites and secondary lymphoid tissues of intranasally immunized BALB/c mice after challenge with murine rotavirus strain EDIM. Initially, this was done by using microarray analysis to quantify mRNAs for 96 murine common cytokines. With this procedure, the synthesis of mRNAs for gamma interferon (IFN-gamma) and interleukin-17 (IL-17) was found to be temporarily upregulated in intestinal lymphoid cells of VP6/LT(R192G)-immunized mice at 12 h after rotavirus challenge. These cytokines were also produced in CD4+ T cells obtained from intestinal sites specific to VP6/LT(R192G)-immunized mice after in vitro exposure to VP6 as determined by intracellular cytokine staining and secretion of cytokines. Although genetically modified mice that lack receptors for either IFN-gamma or IL-17 remained protected after immunization, these results provide suggestive evidence that these cytokines may play direct or indirect roles in protection against rotavirus after mucosal immunization of mice with VP6/LT(R192G).

An essential role for IL-17 in preventing pathogen-initiated bone destruction: recruitment of neutrophils to inflamed bone requires IL-17 receptor-dependent signals

IL-17 and its receptor are founding members of a novel family of inflammatory cytokines. IL-17 plays a pathogenic role in rheumatoid arthritis (RA)-associated bone destruction. However, IL-17 is also an important regulator of host defense through granulopoiesis and neutrophil trafficking. Therefore, the role of IL-17 in pathogen-initiated bone loss was not obvious. The most common form of infection-induced bone destruction occurs in periodontal disease (PD). In addition to causing significant morbidity, PD is a risk factor for atherosclerotic heart disease and chronic obstructive pulmonary disease (COPD). Similar to RA, bone destruction in PD is caused by the immune response. However, neutrophils provide critical antimicrobial defense against periodontal organisms. Since IL-17 is bone destructive in RA but a key regulator of neutrophils, we examined its role in inflammatory bone loss induced by the oral pathogen Porphyromonas gingivalis in IL-17RA-deficient mice. These mice showed enhanced periodontal bone destruction, suggesting a bone-protective role for IL-17, reminiscent of a neutrophil deficiency. Although IL-17RA-deficient neutrophils functioned normally ex vivo, IL-17RA knock-out (IL-17RA(KO)) mice exhibited reduced serum chemokine levels and concomitantly reduced neutrophil migration to bone. Consistently, CXCR2(KO) mice were highly susceptible to alveolar bone loss; interestingly, these mice also suggested a role for chemokines in maintaining normal bone homeostasis. These results indicate a nonredundant role for IL-17 in mediating host defense via neutrophil mobilization.

T cell infiltration after chronic constriction injury of mouse sciatic nerve is associated with interleukin-17 expression

Interleukin (IL)-17A, a recently described novel T cell cytokine, orchestrates inflammation in a variety of immune-mediated diseases. In the present investigation, we analyzed the temporal gene expression pattern of IL-17A and its main regulators IL-23 and IL-15 after chronic constriction injury (CCI) of the sciatic nerve, a lesion paradigm inducing neuropathic pain, by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) in mice. IL-17A displayed a monophasic expression in degenerating nerves at day 7 after CCI while transcripts for the IL-17A regulatory cytokines IL-23 and IL-15 peaked earlier. Accordingly, IL-17A positive T cells were detectable within the endoneurium of the injured nerves by immunocytochemistry. In support of a crucial role of T cell inflammation, RAG-1 knockout mice lacking functional T lymphocytes did not express IL-17A mRNA in distal nerve segments following CCI. Interestingly, T cell deficiency was associated with less thermal hyperalgesia and reduced mRNA levels for the macrophage marker molecule F4/80 and the chemokine macrophage chemoattractant protein-1 (MCP-1) after CCI. Our study supports the notion that T cells and T-cell-derived cytokines contribute to the inflammatory response after peripheral nerve injury.

Interleukin-17 acts independently of TNF-alpha under arthritic conditions

The proinflammatory T cell cytokine IL-17 is a potent inducer of other cytokines such as IL-1 and TNF-alpha. The contribution of TNF in IL-17-induced joint inflammation is unclear. In this work we demonstrate using TNF-alpha-deficient mice that TNF-alpha is required in IL-17-induced joint pathology under naive conditions in vivo. However, overexpression of IL-17 aggravated K/BxN serum transfer arthritis to a similar degree in TNF-alpha-deficient mice and their wild-type counterparts, indicating that the TNF dependency of IL-17-induced pathology is lost under arthritic conditions. Also, during the course of the streptococcal cell wall-induced arthritis model, IL-17 was able to enhance inflammation and cartilage damage in the absence of TNF. Additional blocking of IL-1 during IL-17-enhanced streptococcal cell wall-induced arthritis did not reduce joint pathology in TNF-deficient mice, indicating that IL-1 is not responsible for this loss of TNF dependency. These data provide further understanding of the cytokine interplay during inflammation and demonstrate that, despite a strong TNF dependency under naive conditions, IL-17 acts independently of TNF under arthritic conditions.

Critical role of IL-17 receptor signaling in acute TNBS-induced colitis

BACKGROUND

Inflammatory bowel diseases (IBDs) such as Crohn's disease and ulcerative colitis are characterized by recurrent inflammation in the gastrointestinal tract. Infiltration of CD4 lymphocytes and neutrophils is one of the predominant features of IBD.

MATERIALS AND METHODS

Recently, interleukin (IL)-23 and the downstream T cell-derived cytokine IL-17 have been found to be elevated in intestinal tissue and serum of IBD patients. However, the role of IL-17 and IL-17R signaling in gut inflammation is unknown. To examine this role, we investigated gut inflammation in wild-type or IL-17R knockout mice.

RESULTS

Using a model of acute trinitrobenzenesulfonic acid (TNBS)-induced colitis, we found that IL-17 was produced in colon tissue at 24 and 48 hours and that IL-17R knockout mice were significantly protected against TNBS-induced weight loss, IL-6 production, colonic inflammation, and local macrophage inflammatory protein-2 induction. This protection occurred in the presence of equivalent induction of local IL-23 and higher levels of IL-12p70 and interferon-gamma in IL-17R knockout mice compared with wild-type mice. Moreover, IL-17R knockout mice showed reduced tissue myeloperoxidase activity. Furthermore, overexpression of an IL-17R IgG1 fusion protein significantly attenuated colonic inflammation after acute TNBS.

CONCLUSIONS

These results demonstrate that IL-17R signaling plays a critical role in the development of TNBS-induced colitis and may represent a target for therapeutic intervention for IBD.

Bioactive Thin Film of Acidic Fibroblast Growth Factor Fabricated by Layer-by-Layer Assembly

A new class of bioactive thin films using growth factors as building blocks has been fabricated via layer-by-layer assembly (LBL) technique. Acid fibroblast growth factor (aFGF) in the presence of heparin was used as negatively charged polyelectrolytes, while poly(ethyleneimine) (PEI) was chosen as a positively charged counterpart. The self-deposition process and surface morphology of the resultant multilayers were monitored and detected by UV-vis absorbance spectra, advanced contact angle measurements, and scanning force microscopy (SFM) observations. Cell culture was performed to assess the efficiency of the growth factors. The fibroblasts proliferated faster on the surface assembled with five bilayers of (aFGF/heparin)/PEI with apparent higher cytoviability than on those surfaces modified by one bilayer of (aFGF/heparin)/PEI, five bilayers of aFGF/PEI, or five bilayers of heparin/PEI, and tissue culture polystyrene. Enhanced secretion of collagen type I and interleukin 6 (IL-6) by the fibroblasts seeded on the five bilayers of (aFGF/heparin)/PEI was also verified by immunohistochemical examination. The bioactivity of the (aFGF/heparin)/PEI multilayers could be largely preserved when stored at -20 degrees C.

Interleukin-17 augments tumor necrosis factor-alpha-induced granulocyte and granulocyte/macrophage colony-stimulating factor release from human colonic myofibroblasts

BACKGROUND

Interleukin (IL)-17 is a newly identified T-cell-specific cytokine. In this study, we investigated the effects of IL-17 on colony-stimulating factor (CSF) release in human colonic subepithelial myofibroblasts (SEMFs).

METHODS

CSF release and mRNA expression were determined by enzyme-linked immunosorbent assay (ELISA) and Northern blotting, respectively. Nuclear factor (NF)-kappaB- and activating protein (AP-1)-DNA binding activities were evaluated by electrophoretic gel mobility shift assays (EMSAs).

RESULTS

Unstimulated cells secreted a small amount of granulocyte G- and granulocyte/macrophage (GM)-CSF, and a considerable amount of M-CSF. IL-17 weakly enhanced G-CSF release, but did not affect GM- and M-CSF release. IL-17 selectively enhanced tumor necrosis factor (TNF)-alpha-induced G- and GM-CSF release. The combination of IL-17 plus TNF-alpha induced a marked increase in NF-kappaB- and AP-1-DNA binding activities. The adenovirus-mediated transfer of a stable form of IkappaBalpha and/or a dominant negative mutant of c-Jun markedly inhibited the IL-17 plus TNF-alpha-induced G- and GM-CSF mRNA expression. Furthermore, a stability study showed that IL-17 plus TNF-alpha markedly enhanced the stability of G- and GM-CSF mRNA.

CONCLUSIONS

IL-17 augments TNF-alpha-induced G- and GM-CSF release via transcriptional and posttranscriptional mechanisms.

Interleukin-17 induces hyperresponsive interleukin-8 and interleukin-6 production to tumor necrosis factor-alpha in structural lung cells

Lung epithelial cells contribute to local inflammation by the production of pro-inflammatory mediators like interleukin (IL)-8 and IL-6. Although their production depends on gene transcription, previous studies showed that post-transcriptional mechanisms modulate IL-8 and IL-6 production. Human lung epithelial cells turn from normoresponsive into hyperresponsive IL-8- and IL-6-producing cells when their IL-8 and IL-6 mRNA degradation is reduced. We hypothesized that IL-17, a mediator predominantly released by memory T cells and present in airways of individuals with asthma, would modulate rather than induce IL-8 and IL-6 production by both human lung epithelial cells and fibroblasts. We show here for both cell types that IL-17 was a weak stimulus of IL-8 and IL-6 production, but markedly enhanced IL-8 and IL-6 responses to another stimulus, such as tumor necrosis factor-alpha. This modulatory effect of IL-17 was paralleled by a reduced IL-8 and IL-6 mRNA degradation, with no effect on IL-8 and IL-6 gene transcription. In conclusion, IL-17 particularly affects post-transcriptional regulation of IL-8 and IL-6 expression leading to enhanced IL-8 and IL-6 responses to secondary stimuli, and is only a weak proinflammatory stimulus by itself. This poses the interesting concept that by releasing IL-17 from memory T cells, the adaptive immune system instructs lung structural cells as part of the innate immune system to respond more vigorously.

Cytokines link osteoblasts and inflammation: microarray analysis of interleukin-17- and TNF-alpha-induced genes in bone cells

The novel cytokine interleukin (IL)-17 has been implicated in many infectious and autoimmune settings, especially rheumatoid arthritis. Consistent with its proinflammatory effects on bone, osteoblast cells are highly responsive to IL-17, particularly in combination with other inflammatory cytokines. To better understand the spectrum of activities controlled by IL-17, we globally profiled genes regulated by IL-17 and tumor necrosis factor alpha (TNF-alpha) in the preosteoblast cell line MC3T3-E1. Using Affymetrix microarrays, 80-90 genes were up-regulated, and 19-50 genes were down-regulated with IL-17 and TNF-alpha as compared with TNF-alpha alone. These included proinflammatory chemokines and cytokines, inflammatory genes, transcriptional regulators, bone-remodeling genes, signal transducers, cytoskeletal genes, genes involved in apoptosis, and several unknown or unclassified genes. The CXC family chemokines were most dramatically induced by IL-17 and TNF-alpha, confirming the role of IL-17 as a potent mediator of inflammation and neutrophil recruitment. Several transcription factor-related genes involved in inflammatory gene expression were also enhanced, including molecule possessing ankyrin repeats induced by lipopolysaccharide/inhibitor of kappaBzeta (MAIL/kappaBzeta), CCAAT/enhancer-binding protein delta (C/EBPdelta), and C/EBPbeta. We also identified the acute-phase gene lipocalin-2 (LCN2/24p3) as a novel IL-17 target, which is regulated synergistically by TNF-alpha and IL-17 at the level of its promoter. A similar but not identical pattern of genes was induced by IL-17 and TNF-alpha in ST2 bone marrow stromal cells and murine embryonic fibroblasts. This study provides a profile of genes regulated by IL-17 and TNF-alpha in osteoblasts and suggests that in bone, the major function of IL-17 is to cooperate and/or synergize with other cytokines to amplify inflammation.

Interleukin-17: the missing link between T-cell accumulation and effector cell actions in rheumatoid arthritis?

The prominence of T cells and monocyte/macrophages in rheumatoid synovium suggests T cells may localize and amplify the effector functions of monocyte/macrophages in rheumatoid disease. However, while T cells are abundant in rheumatoid joints, classic T-cell derived cytokines are scarce, especially when compared to the levels of monokines IL-1 beta and TNF-alpha. For this reason, it has been speculated that monocyte/macrophages may act independently of T cells in rheumatoid disease and that the role of T cells may be more or less irrelevant to core disease mechanisms. The question of T-cell influence requires re-evaluation in light of the characterization of IL-17, a T-cell derived cytokine that is abundant in rheumatoid synovium and synovial fluid. IL-17 has a number of pro-inflammatory effects, both directly and through amplification of the effects of IL-1 beta and TNF-alpha. IL-17 is able to induce expression of pro-inflammatory cytokines and stimulate release of eicosanoids by monocytes and synoviocytes. Furthermore, IL-17 has been implicated in the pathogenesis of inflammatory bone and joint damage through induction of matrix metalloproteinases and osteoclasts, as well as inhibition of proteoglycan synthesis. In animal models of arthritis, intra-articular injection of IL-17 results in joint inflammation and damage. The recognition of IL-17 as a pro-inflammatory T cell derived cytokine, and its abundance within rheumatoid joints, provides the strongest candidate mechanism to date through which T cells can capture and localize macrophage effector functions in rheumatoid arthritis. As such, IL-17 warrants consideration for its potential as a therapeutic target in rheumatoid arthritis.

Interleukin-17 regulates expression of the CXC chemokine LIX/CXCL5 in osteoblasts: implications for inflammation and neutrophil recruitment

Interleukin (IL)-17 is the founding member of an emerging family of inflammatory cytokines whose functions remain poorly defined. IL-17 has been linked to the pathogenesis of rheumatoid arthritis, and numerous studies implicate this cytokine in inflammation-induced bone loss. It is clear that a major function of IL-17 is to amplify the immune response by triggering production of chemokines, cytokines, and cell-surface markers, ultimately leading to neutrophil chemotaxis and inflammation. As an IL-17 signaling deficiency in mice causes a dramatic reduction in neutrophil chemotaxis and a consequent increased susceptibility to bacterial infection, it is important to define gene targets involved in IL-17-mediated neutrophil trafficking. Here, we demonstrate that IL-17 and tumor necrosis factor alpha (TNF-alpha) cooperatively induce the lipopolysaccharide-inducible CXC chemokine (LIX; a.k.a., CXC chemokine ligand 5, Scya5, or murine granulocyte chemotactic protein-2) in the preosteoblast cell line MC3T3. LIX is induced rapidly at the mRNA and protein levels, likely through the activation of new gene transcription. Conditioned media from MC3T3 cells treated with IL-17 and/or TNF-alpha stimulates neutrophil mobility potently, and LIX is a significant contributing factor to this process. In addition, IL-17 cooperates with bacterial components involved in periodontal disease to up-regulate LIX expression. This study is the first demonstration of LIX expression in bone cells and has implications for inflammatory bone diseases such as arthritis and periodontal disease.

Respiratory reovirus 1/L induction of intraluminal fibrosis, a model of bronchiolitis obliterans organizing pneumonia, is dependent on T lymphocytes

Bronchiolitis obliterans organizing pneumonia (BOOP) is a clinical syndrome characterized by perivascular/peribronchiolar leukocyte infiltration leading to the development of intraalveolar fibrosis. We have developed an animal model of BOOP where CBA/J mice infected with 1 x 10(6) plaque-forming units (PFU) reovirus 1/L develop follicular bronchiolitis and intraalveolar fibrosis similar to human BOOP. In this report, we demonstrate a role for T cells in the development of intraluminal fibrosis associated with BOOP. Corticosteroid treatment of reovirus 1/L-infected mice both inhibited the development of fibrotic lesions when administered early in the time-course and promoted the resolution of fibrotic lesions when corticosteroid administration was delayed. Further, the depletion of either CD4(+) or CD8(+) T cells before reovirus 1/L infection also inhibited fibrotic lesion development. Both corticosteroid treatment and depletion of CD4(+) or CD8(+) T cells also resulted in decreased expression of the proinflammatory and profibrotic cytokines, interferon (IFN)-gamma and monocyte chemoattractant protein-1 (MCP-1). Further, treatment of mice with a neutralizing monoclonal antibody to IFN-gamma also significantly inhibited the development of fibrosis. Taken together, these results suggest a significant role for T cells in the development of reovirus 1/L-induced BOOP fibrotic lesions in CBA/J mice and suggests that T(H)1-derived cytokines, especially IFN-gamma, may play a key role in fibrotic lesion development.

Interleukin-17 family and IL-17 receptors

Interleukin-17 (IL-17) is a pro-inflammatory cytokine secreted by activated T-cells. Recently discovered related molecules are forming a family of cytokines, the IL-17 family. The prototype member of the family has been designated IL-17A. Due to recent advances in the human genome sequencing and proteomics five additional members have been identified and cloned: IL-17B, IL-17C, IL-17D, IL-17E and IL-17F. The cognate receptors for the IL-17 family identified thus far are: IL-17R, IL-17RH1, IL-17RL (receptor like), IL-17RD and IL-17RE. However, the ligand specificities of many of these receptors have not been established. The IL-17 signaling system is operative in disparate tissues such as articular cartilage, bone, meniscus, brain, hematopoietic tissue, kidney, lung, skin and intestine. Thus, the evolving IL-17 family of ligands and receptors may play an important role in the homeostasis of tissues in health and disease beyond the immune system. This survey reviews the biological actions of IL-17 signaling in cancers, musculoskeletal tissues, the immune system and other tissues.

Differential role for T cells in the development of fibrotic lesions associated with reovirus 1/L-induced bronchiolitis obliterans organizing pneumonia versus Acute Respiratory Distress Syndrome

Bronchiolitis obliterans organizing pneumonia (BOOP) and Acute Respiratory Distress Syndrome (ARDS) are two pulmonary diseases with fibrotic components. BOOP is characterized by perivascular/peribronchiolar leukocyte infiltration leading to the development of intra-alveolar fibrosis. ARDS is a biphasic disease that includes an acute phase, consisting of severe leukocyte infiltration, edema, hemorrhage, and the formation of hyaline membranes, and a chronic phase, which is characterized by persistent intra-alveolar and interstitial fibrosis. CBA/J mice infected with 1 x 10(6) plaque-forming units (pfu) reovirus 1/L develop follicular bronchiolitis and intra-alveolar fibrosis similar to BOOP. In contrast, CBA/J mice infected with 1 x 10(7) pfu reovirus 1/L develop histologic characteristics of ARDS including diffuse alveolar damage, hyaline membranes, and intra-alveolar fibrosis. In this report, we demonstrate a differential role for T lymphocytes in the development of fibrosis associated with BOOP versus ARDS. Neonatally thymectomized CBA/J mice infected with 1 x 10(7) pfu (ARDS) reovirus 1/L still develop the hallmark characteristics of ARDS, including a severe viral pneumonia with cellular infiltrates comprised mainly of macrophages and neutrophils, hyaline membrane formation, and hemorrhage during the acute phase of the disease and persistent intra-alveolar fibrosis during the chronic phase of the disease. In contrast, neonatally thymectomized CBA/J mice infected with 1 x 10(6) pfu (BOOP) reovirus 1/L do not develop intra-alveolar fibrosis associated with BOOP. Therefore, while T cells are necessary for the development of intraluminal fibrosis associated with BOOP, they are not necessary for the development of intraluminal fibrosis associated with ARDS. Furthermore, we suggest that interferon-gamma plays a key role in the fibrotic process and that elevated levels of interferon-gamma are associated with a continuum from least to more severe fibrosis.

Interleukin 17: an example for gene therapy as a tool to study cytokine mediated regulation of hematopoiesis

Interleukin 17 (IL-17) is an essential proinflammatory T-cell derived cytokine with various biological actions. IL-17 was found to have a pivotal role in microbial host defense by interconnecting lymphoid and myeloid host defense. It also acts as a stimulatory hematopoietic cytokine by expanding myeloid progenitors and initiating proliferation of mature neutrophils. This article summarizes results to date on IL-17 research and discusses gene therapy based strategies that were employed to determine its biological functions and significance. A comprehensive working model for IL-17 is introduced.

IL-17 expression in human herpetic stromal keratitis: modulatory effects on chemokine production by corneal fibroblasts

Herpetic stromal keratitis (HSK) is an immunopathologic disease triggered by infection of the cornea with HSV. Key events in HSK involve the interaction between cornea-infiltrating inflammatory cells and resident cells. This interaction, in which macrophages, producing IL-1 and TNF-alpha, and IFN-gamma-producing Th1 cells play a crucial role, results in the local secretion of immune-modulatory factors and a major influx of neutrophils causing corneal lesions and blindness. The Th1-derived cytokine IL-17 has been shown to play an important role in several inflammatory diseases characterized by a massive infiltration of neutrophils into inflamed tissue. Here we show that IL-17 is expressed in corneas from patients with HSK and that the IL-17R is constitutively expressed by human corneal fibroblasts (HCF). IL-17 exhibited a strong synergistic effect with TNF-alpha on the induction of IL-6 and IL-8 secretion by cultured HCF. Secreted IL-8 in these cultures had a strong chemotactic effect on neutrophils. IL-17 also enhanced TNF-alpha- and IFN-gamma-induced secretion of macrophage-inflammatory proteins 1alpha and 3alpha, while inhibiting the induced secretion of RANTES. Furthermore, considerable levels of IFN-gamma-inducible protein 10 and matrix metalloproteinase 1 were measured in stimulated HCF cultures, while the constitutive secretion of monocyte chemotactic protein 1 remained unaffected. The data presented suggest that IL-17 may play an important role in the induction and/or perpetuation of the immunopathologic processes in human HSK by modulating the secretion of proinflammatory and neutrophil chemotactic factors by corneal resident fibroblasts.

Contribution of interleukin 17 to human cartilage degradation and synovial inflammation in osteoarthritis

OBJECTIVE

To compare the effect of interleukin (IL)-17, IL-1beta and TNF-alpha on chemokine production by human chondrocytes and synovial fibroblasts isolated from patients with osteoarthritis (OA). The expression of IL-1beta mRNA by OA chondrocytes was also assessed, as well as the presence and expression of IL-17 receptor (IL-17R) in OA chondrocytes and synovial fibroblasts after stimulation with IL-17, IL-1beta and TNF-alpha.

DESIGN

Synovial fibroblasts and chondrocytes isolated from patients with OA were stimulated in vitro with IL-17, IL-1beta or TNF-alpha. Supernatants were collected and immunoassayed for the presence of IL-8, GRO-alpha (CXC chemokines) and MCP-1, RANTES (CC chemokines). The cells were used to detect the presence of IL-17R and the expression of IL-17R mRNA. Stimulated chondrocytes were also used to detect IL-1beta production and mRNA expression.

RESULTS

IL-17 upregulated the release of IL-8 and GRO-alpha both by synovial fibroblasts and chondrocytes, and the release of MCP-1 only by chondrocytes. IL-17 was a weaker stimulator than IL-1beta and TNF-alpha, except for GRO-alpha release which was maximally upregulated by IL-1beta, less by IL-17 and minimally by TNF-alpha. When compared to IL-1beta, IL-17 was more active on chondrocytes than on fibroblasts. In chondrocytes the expression of IL-1beta mRNA was enhanced by IL-17 and TNF-alpha, with a maximum level reached by IL-1beta. IL-17 and TNF-alpha stimulated IL-1beta release in few subjects. Neither IL-17, IL-1beta nor TNF-alpha modulated the presence of IL-17R and the expression of IL-17R mRNA.

CONCLUSIONS

These data suggest that IL-17 could contribute to cartilage breakdown and synovial infiltration in OA by inducing both the release of chemokines by chondrocytes and synovial fibroblasts and, in a less extent, the synthesis of IL-1beta by chondrocytes.