Role of CD25+ dendritic cells in the generation of Th17 autoreactive T cells in autoimmune experimental uveitis

In the current study, we showed that in vivo administration of an anti-CD25 Ab (PC61) decreased the Th17 response in C57BL/6 mice immunized with the uveitogenic peptide interphotoreceptor retinoid-binding protein, while enhancing the autoreactive Th1 response. The depressed Th17 response was closely associated with decreased numbers of a splenic dendritic cell (DC) subset expressing CD11c(+)CD3(-)CD25(+) and decreased expansion of γδ T cells. We demonstrated that ablation of the CD25(+) DC subset accounted for the decreased activation and the expansion of γδ T cells, leading to decreased activation of IL-17(+) interphotoreceptor retinoid-binding protein-specific T cells. Our results show that an enhanced Th17 response in an autoimmune disease is associated with the appearance of a DC subset expressing CD25 and that treatment of mice with anti-CD25 Ab causes functional alterations in a number of immune cell types, namely DCs and γδ T cells, in addition to CD25(+)αβTCR(+) regulatory T cells.

Serum interleukin-17 & nitric oxide levels in patients with primary Sjögren's syndrome

BACKGROUND & OBJECTIVES

The interleukin (IL)-17 producing T-helper cells have been linked to pathogenesis of autoimmunity and mostly investigated in rheumatoid arthritis (RA). In this study we tested the IL-17 levels, as well as the levels of nitric oxide (NO) as possible IL-17-induced product, in patients with primary Sjögren's syndrome (pSS), an intricate and complex chronic autoimmune disorder of exocrine glands.

METHODS

Serum IL-17 levels and nitrite concentrations determined in patients with pSS (n=30) were compared with the values obtained in patients with RA (n=10) and healthy controls (n=15). The values obtained for IL-17 in pSS patients were also associated with the patients' clinical characteristics, particularly the rheumatoid factor (RF) and total antinuclear antibodies (tANA) levels.

RESULTS

Serum concentrations of IL-17 were significantly (P<0.01) higher in patients with pSS (12.9 ± 28.0 pg/ml) as compared to those obtained in healthy individuals (0.2 ± 0.6 pg/ml), but not as high as the values obtained for the patients with RA (34.5 ± 56.2 pg/ml). The mean IL-17 levels were significantly (P<0.05) higher in the pSS patients positive for rheumatoid factor (20.3 ± 33.3 pg/ml) than in RF-negatives (0.3 ± 0.6 pg/ml). Mean serum concentrations of IL-17 were also higher in antinuclear antibody (ANA)-positive samples (19.8 ± 33.5 pg/ml) in comparison to ANA-negative sera (1.1 ± 3.1 pg/ml) (P<0.05). The NO levels also showed elevated values in both pSS and RA patients, as compared to the healthy controls, since mean nitrite levels in patients with pSS and RA were 38.2 ± 29.2 μM and 41.7 ± 21.1 μM, respectively, while those in healthy controls were significantly lower, at 19.2 ± 10.5 μM.

INTERPRETATION & CONCLUSIONS

The findings of this study showed that there was increased IL-17 and NO production in patients with primary SS, especially if they had associated elevated rheumatoid factor and antinuclear antibody values.

Higher infiltration by Th17 cells compared with regulatory T cells is associated with severe acute T-cell-mediated graft rejection

The aim of this study was to evaluate whether the Th17 and Treg cell infiltration into allograft tissue is associated with the severity of allograft dysfunction and tissue injury in acute T cell-mediated rejection (ATCMR). Seventy-one allograft tissues with biopsy-proven ATCMR were included. The biopsy specimens were immunostained for FOXP3 and IL-17. The allograft function was assessed at biopsy by measuring serum creatinine (Scr) concentration, and by applying the modified diet in renal disease (MDRD) formula, which provides the estimated glomerular filtration rate (eGFR). The severity of allograft tissue injury was assessed by calculating tissue injury scores using the Banff classification. The average numbers of infiltrating Treg and Th17 cells were 11.6 ± 12.2 cells/mm² and 5.6 ± 8.0 cells/mm², respectively. The average Treg/Th17 ratio was 5.6 ± 8.2. The Treg/Th17 ratio was significantly associated with allograft function (Scr and MDRD eGFR) and with the severity of interstitial injury and tubular injury (P < 0.05, all parameters). In separate analyses of the number of infiltrating Treg and Th17 cells, Th17 cell infiltration was significantly associated with allograft function and the severity of tissue injury. By contrast, Treg cell infiltration was not significantly associated with allograft dysfunction or the severity of tissue injury. The results of this study show that higher infiltration of Th17 cell compared with Treg cell is significantly associated with the severity of allograft dysfunction and tissue injury.

CD161-expressing human T cells

Expression of the Natural Killer cell receptor CD161 has recently been identified on a subset of T cells, including both CD4+ T helper and CD8+ T cells. Expression of this molecule within the adult circulation is restricted to those T cells with a memory phenotype. However, the distinct properties of these T cell populations is yet to be fully determined, although expression of CD161 has been related to the secretion of interleukin-17, and therefore to a type 17 phenotype. Recent studies have aimed to determine both the origin of these cells and the significance of CD161 expression as either a marker of specific cell types or as an effector and regulator of lymphocyte function, and hence to characterize the role of these CD161+ cells within a variety of human diseases in which they have been implicated.

Interleukin-17 synergizes with IFNγ or TNFα to promote inflammatory mediator release and intercellular adhesion molecule-1 (ICAM-1) expression in human intervertebral disc cells

Interleukin-17 (IL-17) is a cytokine recently shown to be elevated, along with interferon-γ (IFNγ) and tumor necrosis factor (TNFα), in degenerated and herniated intervertebral disc (IVD) tissues, suggesting a role for these cytokines in intervertebral disc disease. The objective of our study was to investigate the involvement of IL-17 and costimulants IFNγ and TNFα in intervertebral disc pathology. Cells were isolated from anulus fibrosus and nucleus pulposus tissues of patients undergoing surgery for intervertebral disc degeneration or scoliosis. The production of inflammatory mediators, nitric oxide (NOx), prostaglandin E2 (PGE2) and interleukin-6 (IL-6), as well as intercellular adhesion molecule (ICAM-1) expression, were quantified for cultured cells following exposure to IL-17, IFNγ, and TNFα. Intervertebral disc cells exposed to IL-17, IFNγ, or TNFα showed a remarkable increase in inflammatory mediator release and ICAM-1 expression (GLM and ANOVA, p < 0.05). Addition of IFNγ or TNFα to IL-17 demonstrated a synergistic increase in inflammatory mediator release, and a marked increase in ICAM-1 expression. These findings suggest that IVD cells not only respond with a catabolic phenotype to IL-17 and costimulants IFNγ and TNFα, but also express surface ligands with consequent potential to recruit additional lymphocytes and immune cells to the IVD microenvironment. IL-17 may be an important regulator of inflammation in the IVD pathologies.

Macrophages: master regulators of inflammation and fibrosis

Macrophages are found in close proximity with collagen-producing myofibroblasts and indisputably play a key role in fibrosis. They produce profibrotic mediators that directly activate fibroblasts, including transforming growth factor-beta1 and platelet-derived growth factor, and control extracellular matrix turnover by regulating the balance of various matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases. Macrophages also regulate fibrogenesis by secreting chemokines that recruit fibroblasts and other inflammatory cells. With their potential to act in both a pro- and antifibrotic capacity, as well as their ability to regulate the activation of resident and recruited myofibroblasts, macrophages and the factors they express are integrated into all stages of the fibrotic process. These various, and sometimes opposing, functions may be performed by distinct macrophage subpopulations, the identification of which is a growing focus of fibrosis research. Although collagen-secreting myofibroblasts once were thought of as the master "producers" of fibrosis, this review will illustrate how macrophages function as the master "regulators" of fibrosis.

TLR5 signaling stimulates the innate production of IL-17 and IL-22 by CD3(neg)CD127+ immune cells in spleen and mucosa

In adaptive immunity, Th17 lymphocytes produce the IL-17 and IL-22 cytokines that stimulate mucosal antimicrobial defenses and tissue repair. In this study, we observed that the TLR5 agonist flagellin induced swift and transient transcription of genes encoding IL-17 and IL-22 in lymphoid, gut, and lung tissues. This innate response also temporarily enhanced the expression of genes associated with the antimicrobial Th17 signature. The source of the Th17-related cytokines was identified as novel populations of CD3(neg)CD127(+) immune cells among which CD4-expressing cells resembling lymphoid tissue inducer cells. We also demonstrated that dendritic cells are essential for expression of Th17-related cytokines and so for stimulation of innate cells. These data define that TLR-induced activation of CD3(neg)CD127(+) cells and production of Th17-related cytokines may be crucial for the early defenses against pathogen invasion of host tissues.

Anti-Aspergillus human host defence relies on type 1 T helper (Th1), rather than type 17 T helper (Th17), cellular immunity

Both interferon-gamma-producing type 1 T helper (Th1)- and interleukin-17 (IL-17)-producing Th17 cells have been proposed to be involved in anti-fungal host defence. Although invasive aspergillosis is one of the most severe human fungal infections, little is known regarding the relative importance of the Th1 versus Th17 cellular immune pathways for the human anti-Aspergillus host defence. Using human peripheral blood mononuclear cells and a system consisting of monocyte-derived macrophages with lymphocytes, we found that Aspergillus fumigatus is a weak inducer of human IL-17 but induces a strong Th1 response. These data were validated by the very low IL-17 levels in bronchoalveolar lavage fluid and serum of patients with invasive aspergillosis. Surprisingly, live A. fumigatus reduced IL-17 production induced by mitogenic stimuli. This effect was mediated through the propensity of A. fumigatus to metabolize tryptophan and release kynurenine, which modulates the inflammatory response through inhibition of IL-17 production. In conclusion, A. fumigatus does not stimulate production of IL-17 and human host defence against aspergillosis may not rely on potent Th17 responses.

Th17 cytokines interleukin (IL)-17 and IL-22 modulate distinct inflammatory and keratinocyte-response pathways

BACKGROUND

Psoriasis vulgaris is an inflammatory skin disease mediated by Th1 and Th17 cytokines, yet the relative contribution of interferon (IFN)-gamma, interleukin (IL)-17 and IL-22 on disease pathogenesis is still unknown.

OBJECTIVES

In this study, we sought to identify the cytokines produced by skin-resident T cells in normal skin, localize the receptors for these cytokines, and examine how these cytokines alter gene expression profiles of the cells bearing cognate receptors.

METHODS

We used intracellular cytokine staining and flow cytometry to evaluate T cell cytokine production, and immunohistochemistry and double-label immunofluorescence to localize cytokine receptors in skin. Gene array analysis of cytokine-treated keratinocytes was performed using moderated paired t-test controlling for false discovery rate using the Benjamini-Hochberg procedure.

RESULTS

We demonstrate that T-helper cells producing IL-17, IL-22 and/or IFN-gamma, as well as the cells bearing cognate cytokine receptors, are present in normal human skin. Keratinocytes stimulated with IL-17 expressed chemokines that were different from those induced by IFN-gamma, probably contributing to the influx of neutrophils, dendritic cells and memory T cells into the psoriatic lesion. In contrast, IL-22 downregulated genes associated with keratinocyte differentiation and caused epidermal alterations in an organotypic skin model.

CONCLUSIONS

Our results suggest that the Th17 cytokines IL-17 and IL-22 mediate distinct downstream pathways that contribute to the psoriatic phenotype: IL-17 is more proinflammatory, while IL-22 retards keratinocyte differentiation.

Prophylactic and therapeutic suppression of experimental autoimmune encephalomyelitis by a novel bifunctional peptide inhibitor

The objective was to optimize and evaluate the in vivo activities of our novel bifunctional peptide inhibitor (BPI), which alters immune response in autoimmune diseases by modulating the immunological synapse formation. Previously, we have designed PLP-BPI and GAD-BPI by conjugating myelin proteolipid protein (PLP)(139-151) and glutamic acid decarboxylase (GAD)(208-217), respectively, with CD11a(237-246) via a spacer peptide. PLP-BPI and GAD-BPI suppressed the disease progression in experimental autoimmune encephalomyelitis (EAE) and in type-1 diabetes, respectively. In this study, various PLP-BPI derivatives were synthesized and evaluated in the EAE model. Intravenous injections of PLP-BPI derivatives prevented the disease progression more efficiently than did unmodified PLP-BPI. Production of IL-17, a potent proinflammatory cytokine found commonly among MS patients, was significantly low in Ac-PLP-BPI-NH(2)-2-treated mice. Treatment given after the disease onset could dramatically ameliorate the disease. BPI induced anaphylactic responses at a lower incidence than PLP(139-151). In conclusion, PLP-BPI derivatives can effectively suppress the disease severity and morbidity of EAE by post-onset therapeutic treatment as well as prophylactic use.

Interleukin-17 levels in Helicobacter pylori-infected gastric mucosa and pathologic sequelae of colonization

AIM

To determine the role of interleukin (IL)-17 in gastric ulcerogenesis.

METHODS

Thirty-six gastric ulcer (GU) patients and 29 non-ulcer (NU) patients were enrolled in this study. Mucosal biopsy samples were obtained from the gastric antrum and GU site during endoscopy. Samples were used in in situ stimulation for 48 h in the presence of 10 microg/mL phytohemagglutinin-P (PHA), histological examination, and Helicobacter pylori (H pylori) culture. IL-17 and IL-8 protein levels in culture supernatants were assayed by ELISA. IL-17 mRNA expression was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). H pylori cagA and vacA status was assessed by reverse hybridization using a line probe assay (LiPA). IL-8 levels in culture supernatants were assayed after AGS cells were co-cultured with H pylori strain 26,695 or recombinant human (rh) IL-17.

RESULTS

All 36 GU patients and 15 of 29 NU patients were found to be H pylori-positive, while 14 NU patients were H pylori-negative. All 51 H pylori strains from both GU and NU patients were cagA- and vacAs1/m1-positive. Antral mucosal tissues from H pylori-positive patients contained significantly (H pylori-positive NU patients: median 467 pg/mg/protein, range 53-2,499; H pylori-negative NU patients: median 104 pg/mg/protein, range 16-312, P< 0.0005) higher levels of IL-17 than those from uninfected patients. IL-17 levels at the ulcer site were significantly (ulcer site: median 1,356 pg/mg/protein, range 121-1,3730; antrum: median 761 pg/mg/protein, range 24-7,620, P< 0.005) higher than those at distant sites in the antrum. Biopsies from H pylori-positive GU and NU patients showed IL-17 mRNA expression in all samples whereas those from the antrum of the H pylori-negative controls showed no detectable expression. A significant correlation was seen between IL-17 and IL-8 levels at each biopsy site (ulcer: r = 0.62, P< 0.0001; antrum: r = 0.61, P< 0.0001) in GU patients. RhIL-17 and H pylori strain 26,695 each stimulated IL-8 production from AGS cells.

CONCLUSION

IL-17 may play an important role in the inflammatory response to H pylori colonization, and may ultimately influence the outcome of H pylori-associated diseases that arise within the context of gastritis.

Gene expression induced by interleukin-17 in fibroblast-like synoviocytes of patients with rheumatoid arthritis: upregulation of hyaluronan-binding protein TSG-6

Interleukin-17 (IL-17) has been characterized as a proinflammatory cytokine produced by CD4+ CD45RO+ memory T cells. Overproduction of IL-17 was detected in the synovium of patients with rheumatoid arthritis (RA) compared with patients with osteoarthritis. This study examines differentially expressed genes after the stimulation of fibroblast-like synoviocytes of RA patients by IL-17. Among these genes we identified the following: tumor necrosis factor-stimulated gene-6 (TSG-6), IL-6, IL-8, GRO-beta, and bone morphogenetic protein-6 with an expression 3.6-10.6-fold that in the unstimulated control. IL-17 augmented the expression of TSG-6, a hyaluronan-binding protein, in a time- and dose-dependent manner. IL-17 showed additive effects with IL-1beta and tumour necrosis factor-alpha on the expression of TSG-6, IL-6 and IL-8. The mitogen-activated protein kinase p38 seems to be necessary for the regulation of TSG-6 expression by IL-17, as shown by inhibition with SB203580. Our results support the hypothesis that IL-17 is important in the pathogenesis of RA, contributing to an unbalanced production of cytokines as well as participating in connective tissue remodeling.

CD4+ T cells regulate surgical and postinfectious adhesion formation

The development of adhesions in the peritoneal and pelvic cavities, which commonly form after surgery or infection, cause significant morbidity and mortality. However, the pathogenesis of adhesion formation is still poorly understood. Because T cells are important in orchestrating fibrinogenic tissue disorders, we hypothesized that they play a critical role in the pathogenesis of peritoneal adhesion formation. Using a cecal abrasion surgical model in rodents, T cell depletion and adoptive transfer experiments demonstrated that this host response is dependent on CD4+ alphabeta T cells. These cells were also critical to adhesion formation associated with experimental intraabdominal sepsis. T cell transfer studies with mice deficient in signal transducer and activator of transcription (Stat)4 and Stat6 revealed that adhesion formation was dependent on a T helper 1 response. Activated T cells homed to the peritoneal cavity 6 hours after cecal abrasion surgery and predominated at this site during adhesiogenesis. Increased levels of the T cell-derived proinflammatory cytokine interleukin (IL)-17 and of neutrophil chemoattractant CXC chemokines macrophage inflammatory protein-2/CXCL8 and cytokine-induced neutrophil chemoattractant/CXCL1 were associated with adhesion formation. The production of these chemokines was dependent on T cells. Furthermore, the administration of neutralizing antibodies specific for IL-17 or the receptor that binds these CXC chemokines, CXC chemokine receptor 2, significantly reduced the degree of adhesion formation. These results demonstrate for the first time that the immunopathogenesis of adhesion formation is under the control of T cells and that T cell-derived cytokines and chemokines play important roles in the development of this deleterious host response.

IL-17-induced cytokine release in human bronchial epithelial cells in vitro: role of mitogen-activated protein (MAP) kinases

1. Recent data indicate that interleukin (IL)-17 may contribute to neutrophilic airway inflammation by inducing the release of neutrophil-mobilizing cytokines from airway cells. The aim of this study was to evaluate the role of mitogen activated protein kinases in IL-17 induced release of IL-8 and IL-6 in bronchial epithelial cells. 2. Transformed human bronchial epithelial cells (16HBE) were stimulated with either IL-17 or vehicle. Both groups were treated either with SB202190 (inhibitor of p38 MAP kinase), PD98059 (inhibitor of extracellular-signal-regulated kinase [ERK] pathway), Ro-31-7549 (protein kinase C [PKC] inhibitor), LY 294002 (a phosphatidylinositol 3-kinase [PI 3-kinase] inhibitor) or vehicle. IL-6 and IL-8 levels were measured in conditioned media by ELISA. 3. The IL-17-induced release of IL-6 and IL-8 was concentration-dependently inhibited by SB202190 and by PD98059 in bronchial epithelial cells without affecting cell proliferation or survival. 4. Ro-31-7549 and LY294002 had no significant effect on IL-17-induced IL-6 or IL-8 release in bronchial epithelial cells. 4. Taken together, these data indicate a role for p38 and ERK kinase pathways in IL-17-induced release of neutrophil-mobilizing cytokines in human bronchial epithelial cells. These mechanisms constitute potential pharmacotherapeutical targets for inhibition of the IL-17-mediated airway neutrophilia.