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Acute respiratory virus infection (ARI) induces CD8+ T cells with diminished cytokine production and functional impairment. The role of cellular mediators of immune impairment, specifically CD4+ regulatory T cells (Tregs), is incompletely understood in ARI. Tregs are known suppressors of effector T cell function, but whether they are detrimental or beneficial in ARI remains controversial. We show in this paper that Treg depletion leads to increased CD8+ T cell function and lower virus titer in mice infected with human metapneumovirus. We further demonstrate that Tregs play a temporal role in the immune response to human metapneumovirus and influenza: Treg depletion before infection pathologically reduces virus-specific CD8+ T cell numbers and delays virus clearance, whereas depletion 2 d postinoculation enhances CD8+ T cell functionality without reducing virus-specific CD8+ T cell numbers. Mechanistically, Treg depletion during immune priming led to impaired dendritic cell and CD8+ T cell migration. Further, early Treg depletion was associated with immune skewing toward a type 2 phenotype characterized by increased type 2 innate lymphoid cells and TH2 CD4+ T cells, which was not observed when Treg depletion was delayed until after inoculation. These results indicate that the presence of Tregs at inoculation is critical for efficient priming of the CD8+ T cell response to ARI, whereas later in infection, Tregs are dispensable for virus clearance. [ABSTRACT FROM AUTHOR]

Herpetic stromal keratitis (HSK) is characterized by an inflammatory response that includes neutrophils, macrophages, NK cells, and T cells. The factors that are responsible for this inflammation are proinflammatory cytokines and chemokines. Many of these factors have been defined for primary disease, but relatively few have been investigated during recurrent HSK. The present study was designed to determine the role that two of these factors, IL-6 and CXCL1, play during recurrent HSK. Results clearly indicate that unlike primary disease, IL-6 plays no role in recurrent HSK. However, the presence of CXCL1 is required for recurrent HSK as evidenced by the lack of corneal disease in mice treated with anti-CXCL1 Ab. This was confirmed using mice lacking the primary receptor for CXCL1, CXCR2. Corneal disease in this strain was significantly reduced compared with wild-type C57BL/6 controls. Unexpectedly, lack of disease occurs even though CXCL1 knockout mice display increased viral shedding at the cornea. The primary mechanism that CXCL1 plays during disease is its ability to stimulate neutrophils to infiltrate the cornea following reactivation. This paper provides further evidence that primary HSK and recurrent HSK possess overlapping yet distinct disease mechanisms. [ABSTRACT FROM AUTHOR]

GATA-3, a C2C2-type zinc finger transcription factor, regulates many steps of T cell development and differentiation. It is also required for optimal production of type 2 cytokines by CD8+ T cells. However, its role in the development and function of this subset of T cells is still poorly characterized. In this paper, we report that GATA-3 is required for MHC-mediated positive selection and final maturation of CD8 single-positive thymocytes. Deficiency of GATA-3 mediated by a CD4cre transgene led to age-dependent lymphadenopathy partly because of abnormal expansion of CD8+ T cells driven by a cell-extrinsic mechanism. Paradoxically, GATA-3-deficient CD8+ T cells were hyporesponsive to Ag stimulation due to a defect in the maintenance/ progression, but not initiation, of activation signals. More importantly, GATA-3-deficient CD8+ T cells were less efficient in killing Ag-bearing tumor cells in vivo. Taken together, our data further expand the role of GATA-3 in T cells. [ABSTRACT FROM AUTHOR]

Macrophages are an important source of cytokines following infection. Stimulation of macrophages with TLR agonists results in the secretion of TNF-&agr;, IL-6, and IL-12, and the production of these cytokines is controlled by multiple feedback pathways. Macrophages also produce IL-10, which acts to inhibit proinflammatory cytokine production by macrophages via a JAK/STAT3-dependent pathway. We show in this paper that, Ruxolitinib, a recently described selective inhibitor of JAKs, increases TNF, IL-6, and IL-12 secretion in mouse bone marrow-derived macrophages stimulated with LPS. This effect is largely due to its ability to block IL-10-mediated feedback inhibition on cytokine transcription in macrophages. Similar results were also obtained with a second structurally unrelated Jak inhibitor, Tofacitinib. In addition, LPS induced the production of IFN-&bgr;, which was then able to activate JAKs in macrophages, resulting in the stimulation of STATl phosphorylation. The initial induction of IL-10 was independent of JAK signaling; however, inhibition of JAKs did reduce IL-10 secretion at later time points. This reflected a requirement for the IFN-&bgr; feedback loop to sustain IL-10 transcription following LPS stimulation. In addition to IL-10, IFN-ß also helped sustain IL-6 and IL-12 transcription. Overall, these results suggest that inhibition of JAKs may increase the inflammatory potential of macrophages stimulated with TLR4 agonists. [ABSTRACT FROM AUTHOR]

Autocrine IFN-γ signaling is important for CD4 differentiation to Thl effector cells, but it has been unclear whether it contributes to CD8 Τ cell differentiation. We show in this paper that naive murine CD8 Τ cells rapidly and transiently produce low levels of IFN-γ upon stimulation with Ag and B7-1, with production peaking at ∼8 h and declining by 24 h. The autocrine IFN-γ signals for upregulation of expression of T-bet and granzyme Β and induces weak cytolytic activity and effector IFN-γ production. IFN-α acts synergistically with IFN-γ to support development of strong effector functions, whereas IL-12 induces high T-bet expression and strong function in the absence of IFN-γ signaling. Thus, IFN-γ is not only an important CD8 Τ cell effector cytokine, it is an autocrine/paracrine factor whose contributions to differentiation vary depending on whether the response is supported by IL-12 or type I IFN. [ABSTRACT FROM AUTHOR]

The regulators of Gprotein signaling (RGS) protein superfamily negatively controls Gprotein-coupled receptor signal transduction pathways. RGS16 is enriched in activated/effector T lymphocytes. In this paper, we show that RGS16 constrains pulmonary inflammation by regulating chemokine-induced T cell trafficking in response to challenge with Schistosoma mansoni. Naive Rgsl6-/- mice were "primed" for inflammation by accumulation of CCR10+ T cells in the lung. Upon pathogen exposure, these mice developed more robust granulomatous lung fibrosis than wild-type counterparts. Distinct Th2 or putative Thl7 subsets expressing CCR4 or CCR10 accumulated more rapidly in Rgsl6-/- lungs following challenge and produced proinflammatory cytokines IL-13 and IL-17B. CCRA+Rgsl6-/- Th2 cells migrated excessively to CCL17 and localized aberrantly in challenged lungs. T lymphocytes were partially excluded from lung granulomas in Rgsl6-/- mice, instead forming peribronchial/perivascular aggregates. Thus, RGS16-mediated confinement of T cells to Schistosome granulomas mitigates widespread cytokine-mediated pulmonary inflammation. [ABSTRACT FROM AUTHOR]

The glucocorticoid receptor (GR) is a transcription factor able to support either target gene activation via direct binding to DNA or gene repression via interfering with the activity of various proinflammatory transcription factors. An improved therapeutic profile for combating chronic inflammatory diseases has been reported through selectively modulating the GR by only triggering its transrepression function. We have studied in this paper the activity of Compound A (CpdA), a dissociated GR modulator favoring GR monomer formation, in a predominantly Th2-driven asthma model. CpdA acted similarly to the glucocorticoid dexamethasone (DEX) in counteracting OVA-induced airway hyperresponsiveness, recruitment of eosinophils, dendritic cells, neutrophils, B and T cells, and macrophages in bronchoalveolar lavage fluid, lung Th2, Tc2, Thl7, Tc17, and mast cell infiltration, collagen deposition, and goblet cell metaplasia. Both CpdA and DEX inhibited Th2 cytokine production in bronchoalveolar lavage as well as nuclear translocation of NF-&kgr;B and its subsequent recruitment onto the I&kgr;B&agr; promoter in the lung. By contrast, DEX but not CpdA induces expression of the GR-dependent model gene MAPK phosphatase 1 in the lung, confirming the dissociative action of CpdA. Mechanistically, we demonstrate that CpdA inhibited IL-4-induced STAT6 translocation and that GR is essential for CpdA to mediate chemokine repression. In conclusion, we clearly show in this study the anti-inflammatory effect of CpdA in a Th2-driven asthma model in the absence of transactivation, suggesting a potential therapeutic benefit of this strategy. [ABSTRACT FROM AUTHOR]

The innate immune system is equipped with many molecular sensors for microbial DNA/RNA to quickly mount antimicrobial host immune responses. In this paper, we identified DHX9, a DExDc helicase family member, as an important viral dsRNA sensor in myeloid dendritic cells (mDCs). Knockdown of DHX9 expression by small heteroduplex RNA dramatically blocked the ability of mDCs to produce IFN-α/β and proinflammatory cytokines in response to polyinosine-polycytidylic acid, influenza A, and reovirus. DHX9 could specifically bind polyinosine-polycytidylic acid via its double-strand RNA binding motifs. DHX9 interacted with IPS-1 via the HelicC-HA2-DUF and CARD domains of DHX9 and IPS-1, respectively. Knockdown of DHX9 expression in mDCs blocked the activation of NF-κB and IFN regulatory factor 3 by dsRNA. Collectively, these results suggest that DHX9 is an important RNA sensor that is dependent on IPS-1 to sense pathogenic RNA. [ABSTRACT FROM AUTHOR]

Respiratory syncytial virus (RSV) infection is associated with serious lung disease in infants and immunocompromised individuals and is linked to development of asthma. In mice, acute RSV infection causes airway hyperresponsiveness (AHR), inflammation, and mucus hypersecretion. Infected cells induce complement activation, producing the anaphylatoxin C3a. In this paper, we show RSV-infected wild-type mice produce Th17 cytokines, a response not previously associated with viral infections. Mice deficient in the C3aR fail to develop AHR following acute RSV infection, and production of Th17 cytokines was significantly attenuated. Tachykinin production also has been implicated in RSV pathophysiology, and tachykinin receptor-null mice were similarly protected from developing AHR. These animals were also deficient in production of Th17 cytokines. Tachykinin release was absent in mice deficient in C3aR, whereas C3a levels were unchanged in tachykinin receptor-null animals. Thus, our data reveal a crucial sequence following acute RSV infection where initial C3a production causes tachykinin release, followed by activation of the IL-17A pathway. Deficiency of either receptor affords protection from AHR, identifying two potential therapeutic targets. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) competent to express the regulatory enzyme IDO in mice are a small but distinctive subset of DCs. Previously, we reported that a high-dose systemic CpG treatment to ligate TLR9 in vivo induced functional IDO exclusively in splenic CD19+ DCs, which stimulated resting Foxp3-lineage regulatory T cells (Tregs) to rapidly acquire potent suppressor activity. In this paper, we show that IDO was induced in spleen and peripheral lymph nodes after CpG treatment in a dose-dependent manner. Induced IDO suppressed local T cell responses to exogenous Ags and inhibited proinflammatory cytokine expression in response to TLR9 ligation. IDO induction did not occur in T cell-deficient mice or in mice with defective B7 or programmed death (PD)-1 costimulatory pathways. Consistent with these findings, CTLA4 or PD-1/PD-ligand costimulatory blockade abrogated IDO induction and prevented Treg activation via IDO following high-dose CpG treatment. Consequently, CD4+CD25+ T cells uniformly expressed IL-17 shortly after TLR9 ligation. These data support the hypothesis that constitutive interactions from activated T cells or Tregs and IDO-competent DCs via concomitant CTLA4→B7 and PD-1→PD-ligand signals maintain the default potential to regulate T cell responsiveness via IDO. Acute disruption of these nonredundant interactions abrogated regulation via IDO, providing novel perspectives on the proinflammatory effects of costimulatory blockade therapies. Moreover, interactions between IDO-competent DCs and activated T cells in lymphoid tissues may attenuate proinflammatory responses to adjuvants such as TLR ligands. [ABSTRACT FROM AUTHOR]

Autoreactive CD8+ T lymphocytes play a key role in the pathogenesis of several autoimmune diseases. It is not yet well understood how autoreactive CD8+ T cells, which express TCRs with low reactivity toward self-Ags, gain the ability to respond to autoantigens to cause disease. Previously, we have shown that prior stimulation of CD8+ T cells with synergistic combinations of cytokines produced by the innate immune response, such as IL-21 and IL-15, induces Ag-independent proliferation. Such "cytokine-primed" CD8 T cells displayed increased responsiveness to limiting quantities of the cognate Ag. In this paper, we report that prior stimulation with IL-15 and IL-21 also enables CD8+ T cells to respond to weakly agonistic TCR ligands, resulting in proliferation, cytokine secretion, and cytolytic activity. Using a transgenic mouse model of autoimmune diabetes, we show that cytokine-primed autoreactive CD8+ T cells induce disease following stimulation by weak TCR ligands, but their diabetogenic potential is dependent on continuous availability of IL-15 in vivo. These findings suggest that inflammatory cytokines could facilitate the triggering of autoreactive CD8+ T cells by weak autoantigens, and this mechanism may have important implications for autoimmune diseases associated with microbial infections and chronic inflammation. [ABSTRACT FROM AUTHOR]

Overexpression of the T cell cytokine IL-22 is linked to the development of some chronic diseases, but little is known about IL-22 deficiency in humans. As demonstrated in this study, acne inversa (AI; also designated as Hidradenitis suppurativa) lesions show a relative deficiency of IL-22 and IL-20, but not of IL-17A, IL-26, IFN-γ, IL-24, or IL-1β. Moreover, AI lesions had reduced expression of membranous IL-22 and IL-20 receptors and increased expression of the natural IL-22 inhibitor, IL-22 binding protein. AI is a chronic inflammatory skin disease with prevalence up to 4% of the population and in which cutaneous bacterial persistence represents an important pathogenetic factor. Accordingly, we also found a relative deficiency of antimicrobial proteins (AMPs) in AI lesions and a positive correlation between lesional IL-22 and IL-20 versus AMP levels. IL-22, like its tissue cell downstream mediator IL-20, upregulated AMPs in reconstituted human epidermis and was critical for increased AMP levels under inflammatory conditions. The relative IL-22 deficiency in AI was not linked to lesional T cell numbers or Th22/Th1/Th17 subset markers and -inducing cytokines. However, IL-10 was highly expressed in AI lesions and correlated negatively with IL-22 expression. Moreover, IL-10 inhibited IL-22 but not IL-17 production in vitro. The IL-10 overexpression, in turn, was not associated with an elevated presence of regulatory T cells but with the enhanced presence of an IL-10-inducing cytokine. We conclude that IL-22 deficiency may contribute to the pathogenesis of certain chronic disorders as postulated in this paper for AI. [ABSTRACT FROM AUTHOR]

The C5a anaphylatoxin receptor (C5aR; CD88) is activated as part of the complement cascade and exerts important inflammatory, antimicrobial, and regulatory functions, at least in part, via crosstalk with TLRs. However, the periodontal pathogen Porphyromonas gingivalis can control C5aR activation by generating C5a through its own C5 convertase-like enzymatic activity. In this paper, we show that P. gingivalis uses this mechanism to proactively and selectively inhibit TLR2-induced IL-12p70, whereas the same pathogen-instigated C5aR-TLR2 crosstalk upregulates other inflammatory and bone-resorptive cytokines (IL-1β, IL-6, and TNF-α). In vivo, the ability of P. gingivalis to manipulate TLR2 activation via the C5a-C5aR axis allowed it to escape IL-12p70-dependent immune clearance and to cause inflammatory bone loss in a murine model of experimental periodontitis. In the latter regard, C5aR-deficient or TLR2-deficient mice were both resistant to periodontal bone loss, in stark contrast with wild-type control mice, which is consistent with the interdependent interactions of C5aR and TLR2 in P. gingivalis immune evasion and induction of bone-resorptive cytokines. In conclusion, P. gingivalis targets C5aR to promote its adaptive fitness and cause periodontal disease. Given the current availability of safe and effective C5aR antagonists, pharmacological blockade of C5aR could act therapeutically in human periodontitis and reduce associated systemic risks. [ABSTRACT FROM AUTHOR]

Interaction between the nervous and immune systems greatly contributes to inflammatory disease. In organs at the interface between our body and the environment, the sensory neuropeptide substance P (SP) is one key mediator of an acute local stress response through neurogenic inflammation but may also alter cytokine balance and dendritic cell (DC) function. Using a combined murine allergic inflammation/noise stress model with C57BL/6 mice, we show in this paper that SP-released during repeated stress exposure-has the capacity to markedly attenuate inflammation. In particular, repeated stress exposure prior to allergen sensitization increases DC-nerve fiber contacts, enhances DC migration and maturation, alters cytokine balance, and increases levels of IL-2 and T regulatory cell numbers in local lymph nodes and inflamed tissue in a neurokinin 1-SP-receptor (neurokinin-1 receptor)-dependent manner. Concordantly, allergic inflammation is significantly reduced after repeated stress exposure. We conclude that SP/repeated stress prior to immune activation acts protolerogenically and thereby beneficially in inflammation. [ABSTRACT FROM AUTHOR]

Certain virus infections depend on the presence of T cell help for the generation of primary CD8+ T cell responses. However, the mechanisms that render these particular viral infections T cell help dependent is largely unknown. In this study, we compared CD8+ T cell responses elicited by lymphocytic choriomeningitis virus infection, as prototype of a T cell help independent infection, with T cell help dependent CD8+ T cell responses induced by vaccinia virus infection. In this paper, we show that a key parameter decisive for T cell help independence is the ability of an infectious agent to stimulate early and robust production of type I IFN. Experimental provision of type I IFN during VV infection rendered the ensuing CD8+ T cell response completely T cell help independent. Our results support a model in which type I IFN has to be present during the first 3 d of Ag encounter and has to act directly on the responding CD8+ T cells to promote their survival and effector differentiation. We show that type I IFN signaling on responding CD8+ T cells induces profound upregulation of CD25 and increased IL-2 expression; however, neither this nor IL- 15 accounts for the type I IFN effects on responding CD8+ T cells. Thus, type I IFN can effectively replace the requirement of T cell help by directly promoting CD8+ T cell survival and differentiation independent of the type I IFN-induced cytokines IL-2 and IL-15. [ABSTRACT FROM AUTHOR]

The cytokines generated locally in response to infection play an important role in CD8 T cell trafficking, survival, and effector function, rendering these signals prime candidates for immune intervention. In this paper, we show that localized increases in the homeostatic cytokine IL-15 induced by influenza infection is responsible for the migration of CD8 effector T cells to the site of infection. Moreover, intranasal delivery of IL-15-IL-15Rα soluble complexes (IL-15c) specifically restores the frequency of effector T cells lost in the lung airways of IL-15-deficient animals after influenza infection. Exogenous IL-15c quantitatively augments the respiratory CD8 T cell response, and continued administration of IL-15c throughout the contraction phase of the anti-influenza CD8 T cell response magnifies the resultant CD8 T cell memory generated in situ. This treatment extends the ability of these cells to protect against heterologous infection, immunity that typically depreciates over time. Overall, our studies describe what to our knowledge is a new function for IL-15 in attracting effector CD8 T cells to the lung airways and suggest that adjuvanting IL-15 could be used to prolong anti-influenza CD8 T cell responses at mucosal surfaces to facilitate pathogen elimination. [ABSTRACT FROM AUTHOR]

Proper transcriptional control of pro- and anti-inflammatory responses of the immune system is important for a fine-tuned balance between protection and tolerance. Emerging evidence suggests a key role for epigenetic regulation in governing the Th cell differentiation, where effector cytokines direct the overall immune response. In this study, we describe a method to pinpoint the location of isolated human CD4+ T cells on any T cell effector axis based on specific CpG methylation of cytokine and transcription factor loci. We apply the method on CD4+ cells obtained from rheumatoid arthritis and multiple sclerosis patients and show that synovial fluid infiltrating CD4+ T cells are committed toward both Th1 and regulatory T cell phenotype, whereas the Th2 response is suppressed. Furthermore, we show that the IL-17A gene is regulated by promoter methylation and that Th17 commitment is not a common feature in the inflamed joints of rheumatoid arthritis patients. We conclude that the method described in this paper allows for accurate profiling of Th lineage commitment in ex vivo-isolated CD4+ T cells. [ABSTRACT FROM AUTHOR]