Human atopic dermatitis complicated by eczema herpeticum is associated with abnormalities in IFN-γ response

BACKGROUND

The basis for increased susceptibility of patients with atopic dermatitis (AD) to develop disseminated viral skin infections such as eczema herpeticum (AD with a history of eczema herpeticum, ADEH(+)) is poorly understood.

OBJECTIVE

We sought to determine whether subjects with AD prone to disseminated viral skin infections have defects in their IFN responses.

METHODS

GeneChip profiling was used to identify differences in gene expression of PBMCs from patients with ADEH(+) compared with patients with AD without a history of eczema herpeticum (ADEH(-)) and nonatopic controls. Key differences in protein expression were verified by enzyme-linked immunosorbent spot assay and/or ELISA. Clinical relevance was further demonstrated by a mouse model of disseminated viral skin infection and genetic association analysis for genetic variants in IFNG and IFNGR1 and ADEH among 435 cases and controls.

RESULTS

We demonstrate by global gene expression analysis selective transcriptomic changes within the IFN superfamily of PBMCs from subjects with ADEH(+) reflecting low IFN-γ and IFN-γ receptor gene expression. IFN-γ protein production was also significantly lower in patients with ADEH(+) (n = 24) compared with patients with ADEH(-) (n = 20) and nonatopic controls (n = 20). IFN-γ receptor knockout mice developed disseminated viral skin infection after epicutaneous challenge with vaccinia virus. Genetic variants in IFNG and IFNGR1 single nucleotide polymorphisms (SNPs) were significantly associated with ADEH (112 cases, 166 controls) and IFN-γ production: a 2-SNP (A-G) IFNGR1 haplotype (rs10457655 and rs7749390) showed the strongest association with a reduced risk of ADEH+ (13.2% ADEH(+) vs 25.5% ADEH(-); P = .00057).

CONCLUSION

Patients with ADEH(+) have reduced IFN-γ production, and IFNG and IFNGR1 SNPs are significantly associated with ADEH(+) and may contribute to an impaired immune response to herpes simplex virus.

Ameliorated course of glucose-6-phosphate isomerase (G6PI)-induced arthritis in IFN-γ receptor knockout mice exposes an arthritis-promoting role of IFN-γ

The absence of IFN-γ signaling leads to an increased inflammatory response in many murine models of autoimmune diseases induced by a CFA-assisted immunization schedule. We investigated the role of endogenous IFN-γ in arthritis induced by immunization with glucose-6-phosphate isomerase (G6PI) in CFA in DBA/1 mice. Surprisingly, and in contrast to our previous findings in collagen-induced arthritis (CIA), G6PI-induced arthritis was found to be reduced in IFN-γ receptor-deficient (IFN-γR KO) mice, demonstrating a proinflammatory role for IFN-γ in this model. Milder disease in IFN-γR KO mice was associated with less vigorous innate and adaptive immune responses early (day 9) after immunization: less proliferation of myeloid cells in the spleen, less osteoclast formation, less G6PI-reactive Th cells (as measured by ex vivo stimulation and flow cytometry and by in vivo skin reactivity to G6PI) and lower G6PI-specific immunoglobulin serum levels. Surprisingly, on day 21, despite continued milder disease in IFN-γR KO mice, their Th cell responses were no longer diminished but augmented as compared to wild-type mice, and their numbers of immature myeloid splenocytes were also more increased. These data reveal that IFN-γ signaling is critical for the induction of the early immune responses which trigger G6PI-induced arthritis. The strikingly different clinical consequences of absent IFN-γ signaling in G6PI-induced arthritis compared with the very similarly induced CIA emphasize that the role of a single cytokine in experimentally induced arthritis depends critically on the very nature of the inciting (auto)antigen and in particular on the kinetics of the disease manifestation elicited by the antigen.

Effect of amino acid substitutions in the human IFN-γR2 on IFN-γ responsiveness

Patients with interferon-γ receptor (IFN-γR) null mutations have severe infections with poorly pathogenic Mycobacteria. The IFN-γR complex involves two IFN-γR1 and two IFN-γR2 chains, in which several amino acid substitutions, some linked to disease and some apparently naturally occurring, have been described. We developed a model system to study functional effects of genetic variations in IFN-γR2. We retrovirally transduced wild-type IFN-γR2 and IFN-γR2 carrying presently known amino acid substitutions in various human cell lines, and next determined the IFN-γR2 expression pattern as well as IFN-γ responsiveness. We determined that the T58R, Q64R, E147K and K182E variants of IFN-γR2 are fully functional, although the Q64R variant may be expressed higher on the cell membrane. The R114C, T168N and G227R variants were identified in patients that had disseminated infections with non-tuberculous Mycobacteria. Of these genetic variants, T168N was confirmed to be completely non-functional, whereas the novel variant G227R, and the previously reported R114C, were partial functional. The impaired IFN-γ responsiveness of R114C and G227R is mainly due to reduced receptor function, although expression on the cell membrane is reduced as well. We conclude that the T58R, Q64R, E147K and K182E variants are polymorphisms, whereas the R114C, T168N and G227R constitute mutations associated with disease.

Entry of diabetogenic T cells into islets induces changes that lead to amplification of the cellular response

In an accompanying paper, we find specific localization of diabetogenic T cells only to islets of Langerhans bearing the specific antigen. Instrumental in the specific localization was the presence of intraislet dendritic cells bearing the β-cell-peptide-MHC complex. Here, we report that the entry of diabetogenic CD4 T cells very rapidly triggered inflammatory gene expression changes in islets and vessels by up-regulating chemokines and adhesion molecules. Vascular cell adhesion molecule-1 (VCAM-1) expression was notable in blood vessels, as was intercellular adhesion molecule-1 (ICAM-1). ICAM-1 was also found on β-cells. These expression changes induced the entry of nonspecific T cells that otherwise did not localize to the islets. In contrast to the entry of diabetogenic CD4 T cells, the entrance of nonspecific T cells required a chemokine response and VCAM-1 expression by the islets. IFN-γ was important for the early gene expression changes in the islets. By microarray analysis, we detected up-regulation of a group of IFN-inducible genes as early as 8 h post-T-cell transfer. These studies establish that entry of diabetogenic T cells induces a state of receptivity of islets to subsequent immunological insults.

Evidence for a pathophysiological role of keratinocyte-derived type III interferon (IFNλ) in cutaneous lupus erythematosus

Type I IFNs (IFNα/β) have been shown to have a central role in the pathophysiology of lupus erythematosus (LE). The recently discovered type III IFNs (IFNλ1/IL29, IFNλ2/IL28a, IFNλ3/IL28b) share several functional similarities with type I IFNs, particularly in antiviral immunity. As IFNλs act primarily on epithelial cells, we investigated whether type III IFNs might also have a role in the pathogenesis of cutaneous LE (CLE). Our investigations demonstrate that IFNλ and the IFNλ receptor were strongly expressed in the epidermis of CLE skin lesions and related autoimmune diseases (lichen planus and dermatomyositis). Significantly enhanced IFNλ1 could be measured in the serum of CLE patients with active skin lesions. Functional analyses revealed that human keratinocytes are able to produce high levels of IFNλ1 but only low amounts of IFNα/β/γ in response to immunostimulatory nuclear acids, suggesting that IFNλ is a major IFN produced by these cells. Exposure of human keratinocytes to IFNλ1 induced the expression of several proinflammatory cytokines, including CXCL9 (CXC-motiv ligand 9), which drive the recruitment of immune cells and are associated with the formation of CLE skin lesions. Our results provide evidence for a role of type III IFNs in not only antiviral immunity but also autoimmune diseases of the skin.

IFN-γ upregulates survivin and Ifi202 expression to induce survival and proliferation of tumor-specific T cells

BACKGROUND

A common procedure in human cytotoxic T lymphocyte (CTL) adoptive transfer immunotherapy is to expand tumor-specific CTLs ex vivo using CD3 mAb prior to transfer. One of the major obstacles of CTL adoptive immunotherapy is a lack of CTL persistence in the tumor-bearing host after transfer. The aim of this study is to elucidate the molecular mechanisms underlying the effects of stimulation conditions on proliferation and survival of tumor-specific CTLs.

METHODOLOGY/PRINCIPAL FINDINGS

Tumor-specific CTLs were stimulated with either CD3 mAb or cognate Ag and analyzed for their proliferation and survival ex vivo and persistence in tumor-bearing mice. Although both Ag and CD3 mAb effectively induced the cytotoxic effecter molecules of the CTLs, we observed that Ag stimulation is essential for sustained CTL proliferation and survival. Further analysis revealed that Ag stimulation leads to greater proliferation rates and less apoptosis than CD3 mAb stimulation. Re-stimulation of the CD3 mAb-stimulated CTLs with Ag resulted in restored CTL proliferative potential, suggesting that CD3 mAb-induced loss of proliferative potential is reversible. Using DNA microarray technology, we identified that survivin and ifi202, two genes with known functions in T cell apoptosis and proliferation, are differentially induced between Ag- and CD3 mAb-stimulated CTLs. Analysis of the IFN-γ signaling pathway activation revealed that Ag stimulation resulted in rapid phosphorylation of STAT1 (pSTAT1), whereas CD3 mAb stimulation failed to activate STAT1. Chromatin immunoprecipitation revealed that pSTAT1 is associated with the promoters of both survivin and ifi202 in T cells and electrophoresis mobility shift assay indicated that pSTAT1 directly binds to the gamma activation sequence element in the survivin and ifi202 promoters. Finally, silencing ifi202 expression significantly decreased T cell proliferation.

CONCLUSIONS/SIGNIFICANCE

Our findings delineate a new role of the IFN-γ signaling pathway in regulating T cell proliferation and apoptosis through upregulating survivin and ifi202 expression.

The hydroxy-naphthoquinone lapachol arrests mycobacterial growth and immunomodulates host macrophages

The present study reports the anti-mycobacterial activity of 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthoquinone (lapachol) as well as its influence on macrophage functions. Lapachol (L) did not induce apoptosis/necrosis of THP-1 macrophages at ≤32 μg/mL. Mycobacterium avium liquid growth was arrested by ≥32 μg/mL and intra-macrophage proliferation by ≥16 μg/mL lapachol. The main immuno-modulatory effects of lapachol observed were an up-regulation of interferon-γ-receptor 1 (IFN-γR1) and major histocompatibility complex class II (MHCII) surface expression, and a marked inhibition of IL-10 secretion. Lapachol did not affect resting, IFN-γ- or toll-like receptor 2 (TLR2)-induced levels of oxygen and nitrogen metabolism key proteins nor the TLR2-mediated secretion of TNF-α, nor induced either oxidative or endoplasmic reticulum (ER) stress. Lapachol inhibited the surface expression of the co-stimulatory molecule CD86 but not that of CD80 and CD83. The results obtained indicate that the substituted naphthoquinone lapachol exhibits an anti-mycobacterial activity that is more efficient intra- than extra-cellularly, and exerts immuno-modulatory effects some of which may enhance the capacity of the host cell to control mycobacterial growth. The immune-modulatory action of lapachol could contribute to its more efficient intra-macrophage anti-mycobacterial activity.

Interferon gamma in the etiology of atherosclerosis and periodontitis

Clinical observations and a few research reports seem to suggest that intraoral infection as well as periodontal teeth could potentially lead to systemic infections including atherosclerosis. The aim of our investigations was to determine whether periodontal disease might aggravate atherosclerosis and whether interferon-gamma (IFNG), widely recognized as a potent multifunctional cytokine, might serve as a marker of the process. This is the first research based on tissue material such as atheromata and periodontal pocket granulation tissue. The study population consisted of 15 patients with periodontitis and atherosclerosis. Control group comprised 15 non-atherosclerotic patients with periodontitis. IFNG, IFNGR1 and IFNGR2 expression was analysed using qRT-PCR profiling in the inflammatory granulation tissue and atheroma. Granulation tissue samples obtained from non-atherosclerotic group showed a significant increase in IFNG and a decrease of IFNGR1, IFNGR2 expression whereas granulation tissue and atheromata of patients with systemic disease demonstrated lower IFNG and higher IFNGR1 and IFNGR2 expression.

Innate and adaptive immune control of genetically engineered live-attenuated arenavirus vaccine prototypes

Arenaviruses such as Lassa virus (LASV) cause significant morbidity and mortality in endemic areas. Using a glycoprotein (GP) exchange strategy, we have recently developed live-attenuated arenavirus vaccine prototypes (rLCMV/VSVG) based on lymphocytic choriomeningitis virus (LCMV), a close relative of LASV. rLCMV/VSVG induced long-term CD8(+) T cell immunity against wild-type virus challenge and exhibited a stably attenuated phenotype in vivo. Here we elucidated the innate and adaptive immune requirements for the control of rLCMV/VSVG. Infection of RAG(-/-) mice resulted in persisting viral RNA in blood but not in overt viremia. The latter was only found in mice lacking both RAG and IFN type I receptor. Conversely, absence of IFN type II signaling or NK cells on an RAG-deficient background had only minor effects on vaccine virus load or none at all. rLCMV/VSVG infection of wild-type mice induced less type I IFN than did wild-type LCMV, and type I as well as type II IFNs were dispensable for the induction of virus-specific memory CD8 T cells and virus-neutralizing antibodies by rLCMV/VSVG. In conclusion, the adaptive immune systems are essential for elimination of rLCMV/VSVG, and type I but not type II IFN plays a major contributive role in lowering rLCMV/VSVG loads in vivo, attesting to the attenuation profile of the vaccine. Nevertheless, IFNs are not required for the induction of potent vaccine responses. These results provide a better understanding of the immunobiology of rLCMV/VSVG and will contribute to the further development of GP exchange vaccines for combating arenaviral hemorrhagic fevers.

Interleukin-28 and interleukin-29: novel regulators of skin biology

The skin forms an essential barrier between the inside of an organism and the environment. In addition to its function in insulation, temperature regulation, and sensation, it protects the body against physical trauma, pathogens, UV radiation, and excessive water loss. Many processes necessary for maintaining the skin integrity, including antimicrobial/antiviral defense, wound healing, and removal of tumors, are regulated by cytokines. Accumulating results lead us to assume that interleukin (IL)-28 and IL-29, 2 novel members of the IL-10-interferon cytokine family, are important regulators of some of these processes. In the skin, IL-28 and IL-29 can be produced by virus-infected cells, maturing dendritic cells (DCs), and regulatory T-cells, and they mainly influence keratinocytes and melanocytes. In keratinocytes, IL-28 and IL-29 induce growth inhibition. Simultaneously, these cytokines increase the cellular synthesis of proteins that directly hinder virus replication and enhance the readiness to present viral antigens to immune cells. Further, IL-28 and IL-29 upregulate expression of viral and microbial sensing cellular receptors, including toll-like receptor (TLR)3, TLR2, and melanoma differentiation associated gene 5, and strengthen the cellular response to these receptors' ligands. Thereby, in the noninfected skin IL-28 and IL-29 enhance the capacity of keratinocytes to react to viral and microbial products and at least indirectly upregulate their inflammatory potential and innate immunity. IL-28 and IL-29 can act synergistically with other mediators secreted during DC maturation (eg, IL-20). In summary, IL-28/IL-29 may play an important role in the skin in the clearance of viral and microbial infections and in the removal of tumors.

Analysis of functional SNP in ifng/ifngr1 in Chinese Han population with tuberculosis

Ifng/Ifngr1 are the main genes that are associated with tuberculosis. We continued to search for other functional single nucleotide polymorphisms (SNP) and investigated their influence on patients with tuberculosis in the Chinese population. Seven SNP located in the ifng and ifngr1 genes were genotyped by ligase detection reaction in 222 cases and 188 ethnically matched controls. A significant genetic association between rs7749390 (located on the exon/intron splice site of the ifngr1 gene) and tuberculosis was observed, and the log-additive model was accepted as the best inheritance model to fit these data (OR: 1.35, 95% CI: 1.02-1.80, P = 0.038). Haplotype-specific association analysis revealed that the result was consistent with the individual SNP study. The combination of rs2234711/rs1327474/rs7749390/rs41401746, which was in strong linkage disequilibrium (D' > 0.75), showed a significant association of ifngr1 with tuberculosis (P = 0.00079). Neither the single SNP nor the haplotype analysis showed a significant association between tuberculosis and the ifng gene markers. Our data implied the involvement of the ifngr1 gene in susceptibility to tuberculosis.

The CFP-10/ESAT-6 complex of Mycobacterium tuberculosis potentiates the activation of murine macrophages involvement of IFN-gamma signaling

Secretory antigen of Mycobacterium tuberculosis, culture filtered protein 10(CFP-10) and early secreted antigenic target 6 kDa protein (ESAT-6) are closely correlated with immunogenicity and virulence of Mycobacterium tuberculosis. But the mechanism of its immunogenicity and virulence is still unclear. In this study, we investigated the influence of the CFP-10/ESAT-6 complex on production of IL-12 and nitric oxide (NO) produced by the ANA-1 macrophage cell line. Preincubation with the complex in a time-dependent manner significantly enhanced production of NO and IL-12 released from ANA-1 cells following IFN-gamma stimulation. In addition, the complex up-modulated expression level of IFN-gammaR1 on surface of the macrophages. Furthermore, the effect of the complex on production of IL-12 and NO in ANA-1 cells was suppressed by AG490, a selective inhibitor of JAK/STAT pathway. These data suggest that in the presence of IFN-gamma, CFP-10/ESAT-6 complex represents a new immunogenicity and protective factor that may be, at least partly, due to up modulation of IFN-gammaR1 expression and activation of JAK/STAT pathway.

SARS-CoV pathogenesis is regulated by a STAT1 dependent but a type I, II and III interferon receptor independent mechanism

Severe acute respiratory syndrome coronavirus (SARS-CoV) infection often caused severe end stage lung disease and organizing phase diffuse alveolar damage, especially in the elderly. The virus-host interactions that governed development of these acute end stage lung diseases and death are unknown. To address this question, we evaluated the role of innate immune signaling in protection from human (Urbani) and a recombinant mouse adapted SARS-CoV, designated rMA15. In contrast to most models of viral pathogenesis, infection of type I, type II or type III interferon knockout mice (129 background) with either Urbani or MA15 viruses resulted in clinical disease outcomes, including transient weight loss, denuding bronchiolitis and alveolar inflammation and recovery, identical to that seen in infection of wildtype mice. This suggests that type I, II and III interferon signaling play minor roles in regulating SARS pathogenesis in mouse models. In contrast, infection of STAT1-/- mice resulted in severe disease, high virus titer, extensive pulmonary lesions and 100% mortality by day 9 and 30 post-infection with rMA15 or Urbani viruses, respectively. Non-lethal in BALB/c mice, Urbani SARS-CoV infection in STAT1-/- mice caused disseminated infection involving the liver, spleen and other tissues after day 9. These findings demonstrated that SARS-CoV pathogenesis is regulated by a STAT1 dependent but type I, II and III interferon receptor independent, mechanism. In contrast to a well documented role in innate immunity, we propose that STAT1 also protects mice via its role as an antagonist of unrestrained cell proliferation.

IL-17 promotes tumor development through the induction of tumor promoting microenvironments at tumor sites and myeloid-derived suppressor cells

The role of immune responses in tumor development is a central issue for tumor biology and immunology. IL-17 is an important cytokine for inflammatory and autoimmune diseases. Although IL-17-producing cells are detected in cancer patients and tumor-bearing mice, the role of IL-17 in tumor development is controversial, and mechanisms remain to be fully elucidated. In the current study, we found that the development of tumors was inhibited in IL-17R-deficient mice. A defect in IFN-gammaR increased tumor growth, whereas tumor growth was inhibited in mice that were deficient in both IL-17R and IFN-gammaR compared with wild-type animals. Further experiments showed that neutralization of IL-17 by Abs inhibited tumor growth in wild-type mice, whereas systemic administration of IL-17 promoted tumor growth. The IL-17R deficiency increased CD8 T cell infiltration, whereas it reduced the infiltration of myeloid-derived suppressor cells (MDSCs) in tumors. In contrast, administration of IL-17 inhibited CD8 T cell infiltration and increased MDSCs in tumors. Further analysis indicated that IL-17 was required for the development and tumor-promoting activity of MDSCs in tumor-bearing mice. These data demonstrate that IL-17-mediated responses promote tumor development through the induction of tumor-promoting microenvironments at tumor sites. IL-17-mediated regulation of MDSCs is a primary mechanism for its tumor-promoting effects. The study provides novel insights into the role of IL-17 in tumor development and has major implications for targeting IL-17 in treatment of tumors.

Plasma from systemic lupus patients compromises cholesterol homeostasis: a potential mechanism linking autoimmunity to atherosclerotic cardiovascular disease

Atherosclerotic cardiovascular disease (ASCVD) contributes to morbidity and mortality in systemic lupus erythematosus (SLE). Immunologic derangements may disrupt cholesterol balance in vessel wall monocytes/macrophages and endothelium. We determined whether lupus plasma impacts expression of cholesterol 27-hydroxylase, an anti-atherogenic cholesterol-degrading enzyme that promotes cellular cholesterol efflux, in THP-1 human monocytes and primary human aortic endothelial cells (HAEC). THP-1 monocytes and HAEC were incubated in medium containing SLE patient plasma or apparently healthy control human plasma (CHP). SLE plasma decreased 27-hydroxylase message in THP-1 monocytes by 47 +/- 8% (p < 0.008) and in HAEC by 51 +/- 5.5% (n = 5, p < 0.001). THP-1 macrophages were incubated in 25% lupus plasma or CHP and cholesterol-loaded (50 microg ml(-1) acetylated low density lipoprotein). Lupus plasma more than doubled macrophage foam cell transformation (74 +/- 3% vs. 35 +/- 3% for CHP, n = 3, p < 0.001). Impaired cholesterol homeostasis in SLE provides further evidence of immune involvement in atherogenesis. Strategies to inhibit or reverse arterial cholesterol accumulation may benefit SLE patients.

IFN-gamma-receptor signaling ameliorates transplant vasculopathy through attenuation of CD8+ T-cell-mediated injury of vascular endothelial cells

Occlusive transplant vasculopathy (TV) is the major cause for chronic graft rejection. Since endothelial cells (EC) are the first graft cells encountered by activated host lymphocytes, it is important to delineate the molecular mechanisms that coordinate the interaction of EC with activated T cells. Here, the interaction of CD8(+) T cells with Ag-presenting EC in vivo was examined using a transgenic heart transplantation model with beta-galactosidase (beta-gal) expression exclusively in EC (Tie2-LacZ hearts). We found that priming with beta-gal peptide-loaded DC failed to generate a strong systemic IFN-gamma response, but elicited pronounced TV in both IFN-gamma receptor (IFNGR)-competent, and ifngr(-/-) Tie2-LacZ hearts. In contrast, stimulation of EC-specific CD8(+) T cells with beta-gal-recombinant mouse cytomegalovirus (MCMV-LacZ) in recipients of ifngr(+/+) Tie2-LacZ hearts did not precipitate significant TV. However, MCMV-LacZ infection of recipients of ifngr(-/-) Tie2-LacZ hearts led to massive activation of beta-gal-specific CD8 T cells, and led to development of fulminant TV. Further analyses revealed that the strong systemic IFN-gamma "storm" associated with MCMV infection induced upregulation of programmed death-1 ligand 1 (PD-L1) on EC, and subsequent attenuation of programmed death-1 (PD-1)-expressing EC-specific CD8(+) T cells. Thus, IFNGR signaling in ECs activates a potent peripheral negative feedback circuit that protects vascularized grafts from occlusive TV.

Discrepancy between the in vitro and in vivo effects of murine mesenchymal stem cells on T-cell proliferation and collagen-induced arthritis

INTRODUCTION

The goal of this study is to analyze the potential immunosuppressive properties of mesenchymal stem cells (MSC) on T cell proliferation and in collagen-induced arthritis (CIA). An additional aim is to investigate the role of interferon-gamma (IFN-gamma) in these processes.

METHODS

MSC were isolated from bone marrow of DBA/1 wild type and IFN-gamma receptor knock-out (IFN-gammaR KO) mice and expanded in vitro. Proliferation of anti-CD3-stimulated CD4+ T cells in the presence or absence of MSC was evaluated by thymidine incorporation. CIA was induced in DBA/1 mice and animals were treated with MSC by intravenous or intraperitoneal injections of wild type or IFN-gammaR KO MSC.

RESULTS

Purity of enriched MSC cultures was evaluated by flow cytometry and their ability to differentiate into osteoblasts and adipocytes. In vitro, wild type MSC dose-dependently suppressed anti-CD3-induced T cell proliferation whereas IFN-gammaR KO MSC had a significantly lower inhibitory potential. A role for inducible nitric oxide (iNOS), programmed death ligand-1 (PD-L1) and prostaglandin E2 (PGE2), but not indoleamine 2,3-dioxigenase (IDO), in the T cell inhibition was demonstrated. In vivo, neither wild type nor IFN-gammaR KO MSC were able to reduce the severity of CIA or the humoral or cellular immune response toward collagen type II.

CONCLUSIONS

Whereas MSC inhibit anti-CD3-induced proliferation of T cells in vitro, an effect partially mediated by IFN-gamma, MSC do not influence in vivo T cell proliferation nor the disease course of CIA. Thus there is a clear discrepancy between the in vitro and in vivo effects of MSC on T cell proliferation and CIA.

Functional analysis of naturally occurring amino acid substitutions in human IFN-gammaR1

IFN-gamma plays an essential role in the IL-12/IL-23/IFN-gamma pathway that is required for the defense against intracellular pathogens. In the IFN-gammaR1 several amino acid substitutions have been reported that abrogate IFN-gamma signaling. These substitutions can lead to a null phenotype and enhanced susceptibility to infection by poorly pathogenic mycobacteria, a disorder known as Mendelian Susceptibility to Mycobacterial Disease (MSMD). More common amino acid variations in the IFN-gammaR1 may also influence IFN-gammaR function, albeit more subtle. To determine the effect of various amino acid substitutions on IFN-gammaR1 expression and function we cloned two newly identified amino acid substitutions (S149L, I352M), four common variations (V14M, V61I, H335P, L467P), seven reported missense mutations (V61Q, V63G, Y66C, C77Y, C77F, C85Y, I87T) and the 818delTTAA mutation in a retroviral expression vector. IFN-gammaR1 expression was determined as well as responsiveness to IFN-gamma stimulation. The two newly discovered variants, and the four common polymorphisms could be detected on the cell surface, however, the V14M, H335P and I352M variants were significantly lower expressed at the cell membrane, compared to the wild type receptor. Despite the variance in cell surface expression, these IFN-gammaR1 variants did not affect function. In contrast to literature, in our model the expression of the V63G variant was severely reduced and its function was severely impaired but not completely abrogated. In addition, we confirmed the severely reduced function of the I87T mutant receptor, the completely abrogated expression and function of the V61E, V61Q, C77F, C77Y and the C85Y mutations, as well as the overexpression pattern of the 818delTTAA mutant receptor. The Y66C mutation was expressed at the cell surface, it was however, not functional. We conclude that the V14M, V61I, S149L, H335P, I352M and L467P are functional polymorphisms. The other variants are deleterious mutations with V61E, V61Q, Y66C, C77F, C77Y and C85Y leading to complete IFN-gammaR1 deficiency, while V63G and I87T lead to partial IFN-gammaR1 deficiency.

Responsiveness of stromal fibroblasts to IFN-gamma blocks tumor growth via angiostasis

The importance of stromal cells for tumor is akin to soil for seed. However, the interaction among these cells is far from understood. In this study, we show that stromal fibroblasts exist not only during tumor progression but also during regression stage, together with immune effector cells. Coinjection of stromal fibroblasts with tumor cells often promotes tumor growth. However, the presence of IFN-gamma significantly impairs the ability of these cells to promote tumor growth due to a reduced angiogenesis. The mechanism relies mainly on the IFN-gamma-mediated down-regulation of vascular endothelial growth factor production by fibroblasts. The results reveal a novel link between immune cells and nonbone marrow-derived stromal cells, and define stromal fibroblasts as the main targets of IFN-gamma in tumor immunity.

Race between retroviral spread and CD4+ T-cell response determines the outcome of acute Friend virus infection

Retroviruses can establish persistent infection despite induction of a multipartite antiviral immune response. Whether collective failure of all parts of the immune response or selective deficiency in one crucial part underlies the inability of the host to clear retroviral infections is currently uncertain. We examine here the contribution of virus-specific CD4(+) T cells in resistance against Friend virus (FV) infection in the murine host. We show that the magnitude and duration of the FV-specific CD4(+) T-cell response is directly proportional to resistance against acute FV infection and subsequent disease. Notably, significant protection against FV-induced disease is afforded by FV-specific CD4(+) T cells in the absence of a virus-specific CD8(+) T-cell or B-cell response. Enhanced spread of FV infection in hosts with increased genetic susceptibility or coinfection with Lactate dehydrogenase-elevating virus (LDV) causes a proportional increase in the number of FV-specific CD4(+) T cells required to control FV-induced disease. Furthermore, ultimate failure of FV/LDV coinfected hosts to control FV-induced disease is accompanied by accelerated contraction of the FV-specific CD4(+) T-cell response. Conversely, an increased frequency or continuous supply of FV-specific CD4(+) T cells is both necessary and sufficient to effectively contain acute infection and prevent disease, even in the presence of coinfection. Thus, these results suggest that FV-specific CD4(+) T cells provide significant direct protection against acute FV infection, the extent of which critically depends on the ratio of FV-infected cells to FV-specific CD4(+) T cells.

Critical role of IFN-gamma in CFA-mediated protection of NOD mice from diabetes development

IFN-gamma signaling-deficient non-obese diabetic (NOD) mice develop diabetes with similar kinetics to those of wild-type NOD mice. However, the immunization of IFN-gamma signaling-deficient NOD mice with CFA failed to induce long-term protection, whereas wild-type NOD mice receiving CFA remained diabetes-free. CFA also failed to protect IFN-gamma receptor-deficient (IFN-gammaR(-/-)) NOD mice from the autoimmune rejection of transplanted islets, as it does in diabetic NOD mice, and from disease transfer by spleen cells from diabetic NOD mice. These data clearly show that the pro-inflammatory cytokine IFN-gamma is necessary for the CFA-mediated protection of NOD mice from diabetes. There is no difference in the T(h)1/T(h)17 balance between IFN-gammaR(-/-) NOD and wild-type NOD mice. There is also no difference in the total numbers and percentages of regulatory T (Treg) cells in the lymph node CD4(+) T-cell populations between IFN-gammaR(-/-) NOD and wild-type NOD mice. However, pathogenic T cells lacking IFN-gammaR are resistant to the suppressive effect of Treg cells, both in vivo and in vitro. Therefore, it is likely that CFA-mediated protection against diabetes development depends on a change in the balance between Treg cells and pathogenic T cells, and IFN-gamma signaling seems to control the susceptibility of pathogenic T cells to the inhibitory activity of Treg cells.

Bacterial RNA is recognized by different sets of immunoreceptors

Innate immunity recognizes microbial nucleic acids by endosomal TLR and cytosolic recognition systems. Despite increasing knowledge on the properties of nucleic acid recognition for viral RNA and bacterial DNA, little is known about the immunogenicity of prokaryotic RNA. Here we show that bacterial RNA is a potent trigger for type-I IFN secretion in human PBMC. Activation of human plasmacytoid dendritic cells was dependent on endosomal maturation and could be blocked by a TLR7-specific inhibitor. Murine plasmacytoid dendritic cells from TLR7-deficient mice were unresponsive to bacterial RNA. Surprisingly, in myeloid DC, TLR were dispensable for TNF-alpha and IL-12 induction by bacterial RNA. Even non-immune stroma cells were able to mount a NF-kappaB response upon triggering with bacterial RNA. Retinoic-acid inducible gene I and melanoma-differentiation-associated gene 5 could be ruled out to be responsible for this reactivity. Although the inflammasome adaptor protein, apoptosis-associated speck-like protein, and a functional type-I IFN receptor were necessary for IL-1beta secretion in myeloid DC, these proteins were dispensable for TNF-alpha and IL-12 induction by cytosolic bacterial RNA. Our results show that besides of activation of TLR7 and inflammasomes, bacterial RNA activates additional cytosolic receptors similarly as has been reported for recognition of bacterial DNA.

Molecular characterization of novel interferon gamma receptor 1 isoforms in zebrafish (Danio rerio) and goldfish (Carassius auratus L.)

Interferon gamma (IFNgamma) is a highly pleotropic pro-inflammatory and anti-viral cytokine that mediates its effects by binding to a receptor complex composed of interferon gamma receptors 1 and 2 (IFNGR1 and IFNGR2). Using gene synteny analysis, we identified a distinct isoform of the zebrafish IFNGR1. The two zebrafish IFNGR1 called here IFNGR1-1 and IFNGR1-2 were used to identify the respective cDNA sequences of the goldfish IFNGR1-1 and IFNGR1-2. Analysis of protein sequences revealed that all fish IFNGR1 species have potential JAK1 and STAT1 docking sites. Phylogenetically, teleost IFNGR1 proteins grouped separately from those of higher vertebrates. Q-PCR analysis revealed that while the constitutive mRNA levels of the two zebrafish IFNGR1 isoforms were comparable in different tissues examined, the goldfish IFNGR1-1 tissue expression was substantially higher than that of IFNGR1-2. Q-PCR analysis of goldfish immune cell populations revealed highest expression of both receptor isoforms in monocytes. Incubation of goldfish macrophages with recombinant goldfish IFNgamma2 (rgIFNgamma2) up-regulated expression of both IFNGR1-1 and IFNGR1-2, while treatment of cells with rgTNFalpha2 only increased the expression of IFNGR1-1. Treatment with rgTGFbeta resulted in more modest increases in expression of both receptor isoforms only after prolonged treatment. In vitro binding studies indicated that rgIFNGR1-1 bound to rgIFNgamma1 but not rgIFNgamma2, while the rgIFNGR1-2 bound to rgIFNgamma2. Thus, unlike mammals that have a single IFNGR1, cyprinid fish have two distinct IFNGR1 isoforms that preferentially bind corresponding ligands, IFNgamma1 and IFNgamma2, respectively, suggesting that the type II interferon system of these fish species is distinct from that of higher vertebrates.

The search for the IFN-gamma receptor in fish: Functional and expression analysis of putative binding and signalling chains in rainbow trout Oncorhynchus mykiss

Interferons (IFNs), consisting of three major subfamilies, type I, type II (gamma) and type III (lambda) IFN, activate vertebrate antiviral defences once bound to their receptors. The three IFN subfamilies bind to different receptors, IFNAR1 and IFNAR2 for type I IFNs, IFNgammaR1 and IFNgammaR2 for type II IFN, and IL-28R1 and IL-10R2 for type III IFNs. In fish, although many types I and II IFN genes have been cloned, little is known about their receptors. In this report, two putative IFN-gamma receptor chains were identified and sequenced in rainbow trout (Oncorhynchus mykiss), and found to have many common characteristics with mammalian type II IFN receptor family members. The presented gene synteny analysis, phylogenetic tree analysis and ligand binding analysis all suggest that these molecules are the authentic IFNgammaRs in fish. They are widely expressed in tissues, with IFNgammaR1 typically more highly expressed than IFNgammaR2. Using the trout RTG-2 cell line it was possible to show that the individual chains could be differentially modulated, with rIFN-gamma and rIL-1beta down regulating IFNgammaR1 expression but up regulating IFNgammaR2 expression. Over-expression of the two receptor chains in RTG-2 cells revealed that the level of IFNgammaR2 transcript was crucial for responsiveness to rIFN-gamma, in terms of inducing gammaIP expression. Transfection experiments showed that the two putative receptors specifically bound to rIFN-gamma. These findings are discussed in the context of how the IFNgammaR may bind IFN-gamma in fish and the importance of the individual receptor chains to signal transduction.

T cell responses in the absence of IFN-gamma exacerbate uterine infection with Chlamydia trachomatis

Infection with the obligate intracellular bacterium Chlamydia trachomatis is controlled primarily by IFN-gamma and Th1 immunity. In this study, we used cells from a Chlamydia-specific CD4(+) TCR-transgenic mouse to assess the role of IFN-gamma in development of Th1 immunity. We show that secretion of host IFN-gamma or the ability of host cells to respond to secreted IFN-gamma is not required to initiate a Th1 immune response. Additionally, we found that Ag-specific CD4(+) cells that were preskewed toward Th1 confer protection, whereas cells preskewed toward Th2 cause a previously unreported exacerbation of disease leading to higher bacterial load. Chlamydia-specific Th1 cells transferred into an IFN-gamma(-/-) recipient mouse demonstrate protective effects, but the same cells exacerbate bacterial burden when transferred into IFN-gammaR(-/-) mice. Thus, we demonstrate that the secretion of IFN-gamma is necessary for protection against C. trachomatis and that in the absence of host cell IFN-gammaR expression, both Th1 and Th2 cells lead to increased burden of C. trachomatis.