Lijun Xin - Academia.edu (original) (raw)

Papers by Lijun Xin

International Immunopharmacology, 2019

Rheumatoid arthritis (RA) is a representative autoimmune disease characterized by chronic inflamm... more Rheumatoid arthritis (RA) is a representative autoimmune disease characterized by chronic inflammation and joint destruction. Although biological inhibitors such as TNF-α and IL-6 antibodies have achieved success in clinical therapy, small molecule inhibitors against the Janus kinases (JAKs) involved in the signaling pathways of various cytokine receptors have gained more attraction as safe and efficacious options. In this study, we identified CS12192 as a novel selective JAK3/JAK1/TBK1 inhibitor and investigated its pharmacological effects on the experimental arthritis models in rat and mouse. We found that CS12192 showed a more selective inhibitory activity on JAK3, and to a less extent on JAK1 and TBK1, that were verified by decreased activation of p-STATs and p-IRF3 as well as down-regulation of IFN gene expression in the cultured cells with relevant stimuli. Furthermore, oral treatment with CS12192 dose-dependently ameliorated the disease severity, hind paw swelling, body weight loss, and bone destruction in rat models of adjuvant-induced arthritis (AIA) and collagen-induced arthritis (CIA). In a mouse CIA model, CS12192 also attenuated the disease severity, which was correlated with the suppressed CD4 + T cell activation and Th17 function, as well as the reduced cytokine levels in sera and pro-inflammatory cytokine and chemokine gene expression in joint tissue. Corroboratively, RANKL-induced osteoclast formation was inhibited by CS12192. Thus, these results suggest that CS12192 as a novel selective JAK inhibitor has therapeutic potential for the treatment of RA and may provide a new strategy for the control of autoimmune diseases.

Aging cell, Jan 7, 2015

Aging confers increased susceptibility to common pathogens including influenza A virus. Despite s... more Aging confers increased susceptibility to common pathogens including influenza A virus. Despite shared vulnerability to infection with advancing age in humans and rodents, the relatively long time required for immune senescence to take hold practically restricts the use of naturally aged mice to investigate aging-induced immunological shifts. Here, we show accelerated aging Lmna(Dhe) mice with spontaneous mutation in the nuclear scaffolding protein, lamin A, replicate infection susceptibility, and substantial immune cell shifts that occur with advancing age. Naturally aged (≥20 month) and 2- to 3-month-old Lmna(Dhe) mice share near identically increased influenza A susceptibility compared with age-matched Lmna(WT) control mice. Increased mortality and higher viral burden after influenza infection in Lmna(Dhe) mice parallel reduced accumulation of lung alveolar macrophage cells, systemic expansion of immune suppressive Foxp3(+) regulatory T cells, and skewed immune dominance among vi...

International Journal of Molecular Medicine, 2006

Transmembrane tumor necrosis factor-• (mTNF-•) is known to be the precursor of soluble TNF-• (sTN... more Transmembrane tumor necrosis factor-• (mTNF-•) is known to be the precursor of soluble TNF-• (sTNF-•). mTNF-• can act as a ligand on the TNF receptor-(TNFR)bearing cell through 'forward signaling' or as a receptor on the TNF producing cell through 'reverse signaling'. In the current study, we investigated the role of mTNF-•-mediated reverse signaling in regulating sTNF-•-induced activation of human monocytic U937 cells. We demonstrated that pretreatment with sTNFRI, for inducing reverse signaling through mTNF-•, sensitized U937 cells to sTNF-• stimulation, as evidenced by an increase in reactive oxygen production and mRNA levels of proinflammatory cytokines (TNF-•, IL-1ß, and IL-8) in these cells. Further experiments revealed that IκB-• degradation was increased in the monocytic cells primed with sTNFRI, implying that reverse signaling of mTNF-• sensitizes U937 cells via an NF-κB-dependent mechanism. On the other hand, binding of sTNFRI to mTNF-• after sTNF-•-induced activation of U937 cells reduced mRNA stability (half-life) of IL-1ß and IL-8. The involvement of reverse signaling in the process was verified by using a mutated form of mTNF-• lacking the majority of the cytoplasmic domain. Our results clearly showed that enhanced mRNA degradation of the cytokines occurred only in U937 cells transfected with a wild-type mTNF-•, but not in those cells transfected with the mutant mTNF-•. Taken together, these data suggest that reverse signaling through mTNF-• may exert a double role in modulating sTNF-• bioactivity. It is positive when reverse signaling occurs prior to sTNF-• stimulation, while it is negative when reverse signaling occurs after the sTNF-• signal. Thus, our findings strengthen a role of mTNF-•-mediated reverse signaling in the regulation of immune-inflammatory response and control of inflammatory reaction.

Mediators of Inflammation, 2015

Nature, 2012

Pregnancy is an intricately orchestrated process where immune effector cells with fetal specifici... more Pregnancy is an intricately orchestrated process where immune effector cells with fetal specificity are selectively silenced. This requires the sustained expansion of immune suppressive maternal Foxp3 + regulatory T cells (Tregs), because even transient partial ablation triggers fetal-specific effector T cell activation and pregnancy loss 1,2. In turn, many idiopathic pregnancy complications proposed to stem from disrupted fetal tolerance are associated with blunted maternal Treg expansion 3-5. Importantly however, the antigen-specificity and cellular origin of maternal Tregs that accumulate during gestation remain undefined. Here we show pregnancy selectively stimulates the accumulation of maternal Foxp3 + CD4 cells with fetal-specificity using tetramerbased enrichment that allows the identification of rare endogenous T cells 6. Interestingly after delivery, fetal-specific Tregs persist at elevated levels, maintain tolerance to pre-existing fetal antigen, and rapidly re-accumulate during subsequent pregnancy. The accelerated expansion of Tregs during secondary pregnancy was driven almost exclusively by proliferation of fetal-specific Foxp3 + cells retained from prior pregnancy, while induced Foxp3 expression and proliferation of pre-existing Foxp3 + cells each contribute to Treg expansion during primary pregnancy. Furthermore, fetal resorption in secondary compared with primary pregnancy becomes more resilient to partial maternal Foxp3 + cell ablation. Thus, pregnancy imprints Foxp3 + CD4 cells that sustain protective regulatory memory to fetal antigen. We anticipate these findings will spark further investigation on maternal regulatory T cell specificity that unlocks new strategies for improving pregnancy outcomes and novel approaches for therapeutically exploiting regulatory T cell memory. The accumulation of maternal Tregs during pregnancy parallels the need for expanded tolerance to encompass "non-self" fetal antigens 3-5,7,8. However, one consequence of sustained Foxp3 + cell expansion is susceptibility to prenatal infection 2. Given the increasingly recognized importance of Treg specificity in regulating the fluid balance Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

The Journal of clinical investigation, Jan 9, 2015

Mammalian pregnancy requires protection against immunological rejection of the developing fetus b... more Mammalian pregnancy requires protection against immunological rejection of the developing fetus bearing discordant paternal antigens. Immune evasion in this developmental context entails silenced expression of chemoattractant proteins (chemokines), thereby preventing harmful immune cells from penetrating the maternal-fetal interface. Here, we demonstrate that fetal wastage triggered by prenatal Listeria monocytogenes infection is driven by placental recruitment of CXCL9-producing inflammatory neutrophils and macrophages that promote infiltration of fetal-specific T cells into the decidua. Maternal CD8+ T cells with fetal specificity upregulated expression of the chemokine receptor CXCR3 and, together with neutrophils and macrophages, were essential for L. monocytogenes-induced fetal resorption. Conversely, decidual accumulation of maternal T cells with fetal specificity and fetal wastage were extinguished by CXCR3 blockade or in CXCR3-deficient mice. Remarkably, protection against f...

PloS one, 2012

Due to its strong immune stimulatory effects through TLR9, CpG-containing oligodeoxynucleotides (... more Due to its strong immune stimulatory effects through TLR9, CpG-containing oligodeoxynucleotides (CpG ODN) have been tested in multiple clinical trials as vaccine adjuvant for infectious diseases and cancer. However, immune suppression induced by systemic administration of CpGs has been reported recently. In this study, we evaluated the impact of CpGs in an acute rickettsiosis model. We found that systemic treatment with type B CpG (CpG-B), but not type A CpG (CpG-A), at 2 days after sublethal R. australis infection induced mouse death. Although wild-type (WT) B6 and IDO(-/-) mice showed similar survival rates with three different doses of R. australis infection, treatment with CpG-B after sublethal infection consistently induced higher mortality with greater tissue bacterial loads in WT but not IDO(-/-) mice. Also, CpG-B treatment promoted the development of higher serum concentrations of proinflammatory cytokines/chemokines through IDO. Furthermore, while T cell-mediated immune res...

Proceedings of the National Academy of Sciences of the United States of America, Jan 22, 2014

The costimulatory B7-1 (CD80)/B7-2 (CD86) molecules, along with T-cell receptor stimulation, toge... more The costimulatory B7-1 (CD80)/B7-2 (CD86) molecules, along with T-cell receptor stimulation, together facilitate T-cell activation. This explains why in vivo B7 costimulation neutralization efficiently silences a variety of human autoimmune disorders. Paradoxically, however, B7 blockade also potently moderates accumulation of immune-suppressive regulatory T cells (Tregs) essential for protection against multiorgan systemic autoimmunity. Here we show that B7 deprivation in mice overrides the necessity for Tregs in averting systemic autoimmunity and inflammation in extraintestinal tissues, whereas peripherally induced Tregs retained in the absence of B7 selectively mitigate intestinal inflammation caused by Th17 effector CD4(+) T cells. The need for additional immune suppression in the intestine reflects commensal microbe-driven T-cell activation through the accessory costimulation molecules ICOSL and OX40L. Eradication of commensal enteric bacteria mitigates intestinal inflammation a...

REPRODUCTION, 2013

Pregnancy in placental mammals offers exceptional comprehensive benefits ofin uteroprotection, nu... more Pregnancy in placental mammals offers exceptional comprehensive benefits ofin uteroprotection, nutrition, and metabolic waste elimination for the developing fetus. However, these benefits also require durable strategies to mitigate maternal rejection of fetal tissues expressing foreign paternal antigens. Since the initial postulate of expanded maternal immune tolerance by Sir Peter Medawar 60 years ago, an amazingly elaborate assortment of molecular and cellular modifications acting both locally at the maternal–placental interface and systemically have been shown to silence potentially detrimental maternal immune responses. In turn, simultaneously maintaining host defense against the infinite array of potential pathogens during pregnancy is equally important. Fortunately, resistance against most infections is preserved seamlessly throughout gestation. On the other hand, recent studies on pathogens with unique predisposition for prenatal infections have uncovered distinctive holes in...

Molecular Immunology, 2008

We have previously reported a link between a deficient Th1 response to Leishmania amazonensis (La... more We have previously reported a link between a deficient Th1 response to Leishmania amazonensis (La) parasites and profound impairments in the cytokine/chemokine network at early stages of the infection. To define the molecular basis of these deficiencies, we focused on early and intracellular events in La-infected dendritic cells (DCs) in this study. Compared with La promastigote-infected counterparts, amastigote-infected DCs were less mature and less potent as antigen-presenting cells (APC) as evidenced by the lower expression of CD40 and CD83, suppressed cytokine expression (IL-12p40 and IL-10), reduced effectiveness for priming CD4 + T cells from naïve or infected mice. Infection with La promastigotes, but not amastigotes, triggered transient expression of IL-12p40 by DC. Both forms of parasites markedly suppressed IL-12p40, IL-12p70, and IL-6 production and increased IL-10 production when DCs were treated with LPS, IFN-γ/LPS or IFN-α/LPS as positive stimuli. Of note, pre-infection of DCs with live amastigotes resulted in multiple alterations in innate signaling pathways, including degradation of STAT2, decreased phosphorylation of STAT1, 2, 3 and ERK1/2, and markedly reduced expression of interferon regulatory factor-1 (IRF-1) and IRF-8, some of which were partially reversed by pretreatment of parasites with proteasome or protease inhibitors. The impaired IL-12 production in infected DCs was not attributed to increased IL-10 production. Together, our data suggest that La parasites, especially in their intracellular forms, have evolved unique strategies to actively downregulate early innate signaling events, resulting in impaired DC function and Th1 activation.

Journal of Leukocyte Biology, 2013

Although T cell activation has been classically described to require distinct, positive stimulati... more Although T cell activation has been classically described to require distinct, positive stimulation signals that include B7-1 (CD80) and B7-2 (CD86) costimulation, overriding suppression signals that avert immune-mediated host injury are equally important. How these opposing stimulation and suppression signals work together remains incompletely defined. Our recent studies demonstrate that CD8 Teff activation in response to cognate peptide stimulation is actively suppressed by the Foxp3+ subset of CD4 cells, called Tregs. Here, we show that the elimination of Treg suppression does not bypass the requirement for positive B7-1/B7-2 costimulation. The expansion, IFN-γ cytokine production, cytolytic, and protective features of antigen-specific CD8 T cells stimulated with purified cognate peptide in Treg-ablated mice were each neutralized effectively by CTLA-4-Ig that blocks B7-1/B7-2. In turn, given the efficiency whereby CTLA-4-Ig overrides the effects of Treg ablation, the role of Foxp...

The Journal of Immunology, 2010

Type I IFNs exert diverse effector and regulatory functions in host immunity to viral and nonvira... more Type I IFNs exert diverse effector and regulatory functions in host immunity to viral and nonviral infections; however, the role of endogenous type I IFNs in leishmaniasis is unclear. We found that type I IFNR-deficient (IFNAR−/−) mice developed attenuated lesions and reduced Ag-specific immune responses following infection with Leishmania amazonensis parasites. The marked reduction in tissue parasites, even at 3 d in IFNAR−/− mice, seemed to be indicative of an enhanced innate immunity. Further mechanistic analyses indicated distinct roles for neutrophils in parasite clearance; IFNAR−/− mice displayed a rapid and sustained infiltration of neutrophils, but a limited recruitment of CD11b+Ly-6C+ inflammatory monocytes, into inflamed tissues; interactions between IFNAR−/−, but not wild-type (WT) or STAT1−/−, neutrophils and macrophages greatly enhanced parasite killing in vitro; and infected IFNAR−/− neutrophils efficiently released granular enzymes and had elevated rates of cell apopt...

The Journal of Immunology, 2010

The nature and differentiation of regulatory CD8+CD28− T cells are poorly understood. In this stu... more The nature and differentiation of regulatory CD8+CD28− T cells are poorly understood. In this study, we demonstrate that native Ag trichosanthin (Tk), a highly purified linear peptide isolated from a Chinese medicinal herb, is able to induce strong suppression of OVA-specific lymphoproliferation at low concentrations via activation of IL-4/IL-10–secreting CD8+CD28− regulatory T cells (Tregs). To elucidate the underlying mechanisms, we firstly identified two types of mouse inbred strains, high susceptible (HS) and low susceptible, for the Tk-related suppression. They are H-2d (or H-2b) and H-2k, respectively. The suppression is evoked only if bone marrow-derived dendritic cells (BDCs) instead of purified T cells are treated with Tk in an OVA-specific T-BDC interaction. Moreover, a special pattern of cytokine/transcription factors (IL-4+IL-10+IFN-γ−Gata3+T-bet−) during suppressed OVA-specific T cell proliferation was observed in HS C57BL/6 but not in low-susceptible C3H/He mice. Consi...

The Journal of Immunology, 2006

It has been demonstrated in our previous work that, in the human skin-grafting model, the express... more It has been demonstrated in our previous work that, in the human skin-grafting model, the expression of costimulatory molecule B7H1 (PD-L1) by keratinocytes plays an essential role in inducing local tolerance via activation of IL-10-secreting T cells. This study further analyzes the role of B7H1 in differentiation of type 1 T regulatory (Tr1) cells and explores underlying mechanisms. Mouse fusion protein B7H1-Ig is used, together with immobilized anti-CD3 mAb, to costimulate the purified naive CD4+ T cells. B7H1-Ig-treated CD4+ T cells were found to activate a characteristic Tr1 population possessing a CD4+CD25−Foxp3− CD45RBlow phenotype. These regulatory T cells strongly inhibited the Th1-dominated MLR by secretion of IL-10 and TGF-β. Moreover, B7H1-treated Tr1 cells also resulted in suppressed clinical scores and demyelination when adoptively transferred into mice with experimental allergic encephalomyelitis. Furthermore, analysis of the cytokine profile indicated that there were ...

The Journal of Immunology, 2008

Leishmania (Viannia) braziliensis is the causative agent of cutaneous and mucosal leishmaniasis i... more Leishmania (Viannia) braziliensis is the causative agent of cutaneous and mucosal leishmaniasis in South America, and the latter is a severe and disfiguring form of the disease. Our understanding of how L. braziliensis parasites interact with dendritic cells (DCs) is limited, partially due to the difficulty in generating axenic amastigotes. In this study, we successfully generated axenic amastigotes of L. braziliensis and used them to test the hypothesis that L. braziliensis infection efficiently triggers innate responses in DCs and the subsequent adaptive immune responses for parasite clearance. This study has revealed unique immunological features of L. braziliensis infection. Firstly, axenic amastigotes showed higher infectivity and the potential to stimulate C57BL/6 (B6) bone marrow-derived dendritic cells to produce IL-12p40 when compared with their promastigote counterparts. Both parasite-carrying and bystander DCs displayed an activated (CD11chighCD45RB−CD83+CD40+CD80+) pheno...

International Journal for Parasitology, 2008

Leishmania amazonensis infection, occurring predominantly in Central and South America, can manif... more Leishmania amazonensis infection, occurring predominantly in Central and South America, can manifest itself in several forms, including those of cutaneous and diffuse cutaneous leishmaniasis. The outcome of L. amazonensis infection depends largely on host immune responses to the parasites. While CD4 + T cell activation is a prerequisite for pathogenesis in L. amazonensis-infected mice, the roles of B cells and their antibody production are unclear. In this study, we provide evidence suggesting that B cells and antibodies are involved in disease pathogenesis. We documented a correlation between B cell activation and lesion progress in immunocompetent mice. In the absence of functional B cells and antibodies, JhD mice showed a delayed onset of disease and developed small lesions. Histological examination of these mice revealed a significant reduction in CD4 + and CD8 + T cells, but not in MAC1 + macrophages, at the infection site. In contrast to the wild-type mice that showed typical tissue necrosis, L. amazonensis-infected JhD mice showed no or minimal signs of necrotic foci. A marked reduction in CD4 + T cell proliferation and cytokine (IFN-c and IL-10) production in infected JhD mice suggested an involvement of B cells and antibodies in the priming of parasite-specific T cells. This notion was further supported by the observations that adoptive transfer of B cells or antibodies could restore CD4 + T cell activation and migration in infected JhD mice. Moreover, antibody coating of parasites could stimulate dendritic cells to produce high levels of cytokines and increase their ability to prime naïve CD4 + T cells. Since CD4 + T cells are crucial to disease pathogenesis, this study suggests that B cells and their antibody production enhanced L. amazonensis infection, partially by promoting T cell priming and cellular migration to the infection site.

Infection and Immunity, 2011

Leishmania parasites alternate between flagellated promastigotes in sand flies and nonflagellated... more Leishmania parasites alternate between flagellated promastigotes in sand flies and nonflagellated amastigotes in mammals, causing a spectrum of serious diseases. To survive, they must resist the harsh conditions in phagocytes (including acidic pH, elevated temperature, and increased oxidative/nitrosative stress) and evade the immune response. Recent studies have highlighted the importance of sphingolipid (SL) metabolism in Leishmania virulence. In particular, we have generated a Leishmania major iscl − mutant which is deficient in SL degradation but grows normally as promastigotes in culture. Importantly, iscl − mutants cannot induce pathology in either immunocompetent or immunodeficient mice yet are able to persist at low levels. In this study, we investigated how the degradation of SLs might contribute to Leishmania infection. First, unlike wild-type (WT) L. major , iscl − mutants do not trigger polarized T cell responses in mice. Second, like WT parasites, iscl − mutants possess ...

Infection and Immunity, 2009

We have previously reported that Leishmania braziliensis infection can activate murine dendritic ... more We have previously reported that Leishmania braziliensis infection can activate murine dendritic cells (DCs) and upregulate signaling pathways that are essential for the initiation of innate immunity. However, it remains unclear whether Toll-like receptors (TLRs) are involved in L. braziliensis -mediated DC activation. To address this issue, we generated bone marrow-derived DCs from MyD88 −/− and TLR2 −/− mice and examined their responsiveness to parasite infection. While wild-type DCs were efficiently activated to produce cytokines and prime naïve CD4 + T cells, L. braziliensis -infected MyD88 −/− DCs exhibited less activation and decreased production of interleukin-12 (IL-12) p40. Furthermore, MyD88 −/− mice were more susceptible to infection in that they developed larger and prolonged lesions compared to those in control mice. In sharp contrast, the lack of TLR2 resulted in an enhanced DC activation and increased IL-12 p40 production after infection. As such, L. braziliensis -in...

Infection and Immunity, 2007

Leishmania amazonensis can cause progressive disease in most inbred strains of mice. We have prev... more Leishmania amazonensis can cause progressive disease in most inbred strains of mice. We have previously reported that treatment with CXCL10 activates macrophage (MΦ) effector function(s) in parasite killing and significantly delays lesion development in susceptible C57BL/6 mice via enhanced gamma interferon (IFN-γ) and interleukin 12 (IL-12) secretion; however, the mechanism underlying this enhanced immunity against L. amazonensis infection remains largely unresolved. In this study, we utilized stationary promastigotes to infect bone marrow-derived dendritic cells (DCs) of C57BL/6 mice and assessed the activation of DC subsets and the capacity of these DC subsets to prime CD4 + T cells in vitro. We found that CXCL10 induced IL-12 p40 production but reduced IL-10 production in uninfected DCs. Yet L. amazonensis -infected DCs produced elevated levels of IL-10 despite CXCL10 treatment. Elimination of endogenous IL-10 led to increased IL-12 p40 production in DCs as well as increased pro...

International Immunopharmacology, 2019

Rheumatoid arthritis (RA) is a representative autoimmune disease characterized by chronic inflamm... more Rheumatoid arthritis (RA) is a representative autoimmune disease characterized by chronic inflammation and joint destruction. Although biological inhibitors such as TNF-α and IL-6 antibodies have achieved success in clinical therapy, small molecule inhibitors against the Janus kinases (JAKs) involved in the signaling pathways of various cytokine receptors have gained more attraction as safe and efficacious options. In this study, we identified CS12192 as a novel selective JAK3/JAK1/TBK1 inhibitor and investigated its pharmacological effects on the experimental arthritis models in rat and mouse. We found that CS12192 showed a more selective inhibitory activity on JAK3, and to a less extent on JAK1 and TBK1, that were verified by decreased activation of p-STATs and p-IRF3 as well as down-regulation of IFN gene expression in the cultured cells with relevant stimuli. Furthermore, oral treatment with CS12192 dose-dependently ameliorated the disease severity, hind paw swelling, body weight loss, and bone destruction in rat models of adjuvant-induced arthritis (AIA) and collagen-induced arthritis (CIA). In a mouse CIA model, CS12192 also attenuated the disease severity, which was correlated with the suppressed CD4 + T cell activation and Th17 function, as well as the reduced cytokine levels in sera and pro-inflammatory cytokine and chemokine gene expression in joint tissue. Corroboratively, RANKL-induced osteoclast formation was inhibited by CS12192. Thus, these results suggest that CS12192 as a novel selective JAK inhibitor has therapeutic potential for the treatment of RA and may provide a new strategy for the control of autoimmune diseases.

Aging cell, Jan 7, 2015

Aging confers increased susceptibility to common pathogens including influenza A virus. Despite s... more Aging confers increased susceptibility to common pathogens including influenza A virus. Despite shared vulnerability to infection with advancing age in humans and rodents, the relatively long time required for immune senescence to take hold practically restricts the use of naturally aged mice to investigate aging-induced immunological shifts. Here, we show accelerated aging Lmna(Dhe) mice with spontaneous mutation in the nuclear scaffolding protein, lamin A, replicate infection susceptibility, and substantial immune cell shifts that occur with advancing age. Naturally aged (≥20 month) and 2- to 3-month-old Lmna(Dhe) mice share near identically increased influenza A susceptibility compared with age-matched Lmna(WT) control mice. Increased mortality and higher viral burden after influenza infection in Lmna(Dhe) mice parallel reduced accumulation of lung alveolar macrophage cells, systemic expansion of immune suppressive Foxp3(+) regulatory T cells, and skewed immune dominance among vi...

International Journal of Molecular Medicine, 2006

Transmembrane tumor necrosis factor-• (mTNF-•) is known to be the precursor of soluble TNF-• (sTN... more Transmembrane tumor necrosis factor-• (mTNF-•) is known to be the precursor of soluble TNF-• (sTNF-•). mTNF-• can act as a ligand on the TNF receptor-(TNFR)bearing cell through 'forward signaling' or as a receptor on the TNF producing cell through 'reverse signaling'. In the current study, we investigated the role of mTNF-•-mediated reverse signaling in regulating sTNF-•-induced activation of human monocytic U937 cells. We demonstrated that pretreatment with sTNFRI, for inducing reverse signaling through mTNF-•, sensitized U937 cells to sTNF-• stimulation, as evidenced by an increase in reactive oxygen production and mRNA levels of proinflammatory cytokines (TNF-•, IL-1ß, and IL-8) in these cells. Further experiments revealed that IκB-• degradation was increased in the monocytic cells primed with sTNFRI, implying that reverse signaling of mTNF-• sensitizes U937 cells via an NF-κB-dependent mechanism. On the other hand, binding of sTNFRI to mTNF-• after sTNF-•-induced activation of U937 cells reduced mRNA stability (half-life) of IL-1ß and IL-8. The involvement of reverse signaling in the process was verified by using a mutated form of mTNF-• lacking the majority of the cytoplasmic domain. Our results clearly showed that enhanced mRNA degradation of the cytokines occurred only in U937 cells transfected with a wild-type mTNF-•, but not in those cells transfected with the mutant mTNF-•. Taken together, these data suggest that reverse signaling through mTNF-• may exert a double role in modulating sTNF-• bioactivity. It is positive when reverse signaling occurs prior to sTNF-• stimulation, while it is negative when reverse signaling occurs after the sTNF-• signal. Thus, our findings strengthen a role of mTNF-•-mediated reverse signaling in the regulation of immune-inflammatory response and control of inflammatory reaction.

Mediators of Inflammation, 2015

Nature, 2012

Pregnancy is an intricately orchestrated process where immune effector cells with fetal specifici... more Pregnancy is an intricately orchestrated process where immune effector cells with fetal specificity are selectively silenced. This requires the sustained expansion of immune suppressive maternal Foxp3 + regulatory T cells (Tregs), because even transient partial ablation triggers fetal-specific effector T cell activation and pregnancy loss 1,2. In turn, many idiopathic pregnancy complications proposed to stem from disrupted fetal tolerance are associated with blunted maternal Treg expansion 3-5. Importantly however, the antigen-specificity and cellular origin of maternal Tregs that accumulate during gestation remain undefined. Here we show pregnancy selectively stimulates the accumulation of maternal Foxp3 + CD4 cells with fetal-specificity using tetramerbased enrichment that allows the identification of rare endogenous T cells 6. Interestingly after delivery, fetal-specific Tregs persist at elevated levels, maintain tolerance to pre-existing fetal antigen, and rapidly re-accumulate during subsequent pregnancy. The accelerated expansion of Tregs during secondary pregnancy was driven almost exclusively by proliferation of fetal-specific Foxp3 + cells retained from prior pregnancy, while induced Foxp3 expression and proliferation of pre-existing Foxp3 + cells each contribute to Treg expansion during primary pregnancy. Furthermore, fetal resorption in secondary compared with primary pregnancy becomes more resilient to partial maternal Foxp3 + cell ablation. Thus, pregnancy imprints Foxp3 + CD4 cells that sustain protective regulatory memory to fetal antigen. We anticipate these findings will spark further investigation on maternal regulatory T cell specificity that unlocks new strategies for improving pregnancy outcomes and novel approaches for therapeutically exploiting regulatory T cell memory. The accumulation of maternal Tregs during pregnancy parallels the need for expanded tolerance to encompass "non-self" fetal antigens 3-5,7,8. However, one consequence of sustained Foxp3 + cell expansion is susceptibility to prenatal infection 2. Given the increasingly recognized importance of Treg specificity in regulating the fluid balance Users may view, print, copy, download and text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

The Journal of clinical investigation, Jan 9, 2015

Mammalian pregnancy requires protection against immunological rejection of the developing fetus b... more Mammalian pregnancy requires protection against immunological rejection of the developing fetus bearing discordant paternal antigens. Immune evasion in this developmental context entails silenced expression of chemoattractant proteins (chemokines), thereby preventing harmful immune cells from penetrating the maternal-fetal interface. Here, we demonstrate that fetal wastage triggered by prenatal Listeria monocytogenes infection is driven by placental recruitment of CXCL9-producing inflammatory neutrophils and macrophages that promote infiltration of fetal-specific T cells into the decidua. Maternal CD8+ T cells with fetal specificity upregulated expression of the chemokine receptor CXCR3 and, together with neutrophils and macrophages, were essential for L. monocytogenes-induced fetal resorption. Conversely, decidual accumulation of maternal T cells with fetal specificity and fetal wastage were extinguished by CXCR3 blockade or in CXCR3-deficient mice. Remarkably, protection against f...

PloS one, 2012

Due to its strong immune stimulatory effects through TLR9, CpG-containing oligodeoxynucleotides (... more Due to its strong immune stimulatory effects through TLR9, CpG-containing oligodeoxynucleotides (CpG ODN) have been tested in multiple clinical trials as vaccine adjuvant for infectious diseases and cancer. However, immune suppression induced by systemic administration of CpGs has been reported recently. In this study, we evaluated the impact of CpGs in an acute rickettsiosis model. We found that systemic treatment with type B CpG (CpG-B), but not type A CpG (CpG-A), at 2 days after sublethal R. australis infection induced mouse death. Although wild-type (WT) B6 and IDO(-/-) mice showed similar survival rates with three different doses of R. australis infection, treatment with CpG-B after sublethal infection consistently induced higher mortality with greater tissue bacterial loads in WT but not IDO(-/-) mice. Also, CpG-B treatment promoted the development of higher serum concentrations of proinflammatory cytokines/chemokines through IDO. Furthermore, while T cell-mediated immune res...

Proceedings of the National Academy of Sciences of the United States of America, Jan 22, 2014

The costimulatory B7-1 (CD80)/B7-2 (CD86) molecules, along with T-cell receptor stimulation, toge... more The costimulatory B7-1 (CD80)/B7-2 (CD86) molecules, along with T-cell receptor stimulation, together facilitate T-cell activation. This explains why in vivo B7 costimulation neutralization efficiently silences a variety of human autoimmune disorders. Paradoxically, however, B7 blockade also potently moderates accumulation of immune-suppressive regulatory T cells (Tregs) essential for protection against multiorgan systemic autoimmunity. Here we show that B7 deprivation in mice overrides the necessity for Tregs in averting systemic autoimmunity and inflammation in extraintestinal tissues, whereas peripherally induced Tregs retained in the absence of B7 selectively mitigate intestinal inflammation caused by Th17 effector CD4(+) T cells. The need for additional immune suppression in the intestine reflects commensal microbe-driven T-cell activation through the accessory costimulation molecules ICOSL and OX40L. Eradication of commensal enteric bacteria mitigates intestinal inflammation a...

REPRODUCTION, 2013

Pregnancy in placental mammals offers exceptional comprehensive benefits ofin uteroprotection, nu... more Pregnancy in placental mammals offers exceptional comprehensive benefits ofin uteroprotection, nutrition, and metabolic waste elimination for the developing fetus. However, these benefits also require durable strategies to mitigate maternal rejection of fetal tissues expressing foreign paternal antigens. Since the initial postulate of expanded maternal immune tolerance by Sir Peter Medawar 60 years ago, an amazingly elaborate assortment of molecular and cellular modifications acting both locally at the maternal–placental interface and systemically have been shown to silence potentially detrimental maternal immune responses. In turn, simultaneously maintaining host defense against the infinite array of potential pathogens during pregnancy is equally important. Fortunately, resistance against most infections is preserved seamlessly throughout gestation. On the other hand, recent studies on pathogens with unique predisposition for prenatal infections have uncovered distinctive holes in...

Molecular Immunology, 2008

We have previously reported a link between a deficient Th1 response to Leishmania amazonensis (La... more We have previously reported a link between a deficient Th1 response to Leishmania amazonensis (La) parasites and profound impairments in the cytokine/chemokine network at early stages of the infection. To define the molecular basis of these deficiencies, we focused on early and intracellular events in La-infected dendritic cells (DCs) in this study. Compared with La promastigote-infected counterparts, amastigote-infected DCs were less mature and less potent as antigen-presenting cells (APC) as evidenced by the lower expression of CD40 and CD83, suppressed cytokine expression (IL-12p40 and IL-10), reduced effectiveness for priming CD4 + T cells from naïve or infected mice. Infection with La promastigotes, but not amastigotes, triggered transient expression of IL-12p40 by DC. Both forms of parasites markedly suppressed IL-12p40, IL-12p70, and IL-6 production and increased IL-10 production when DCs were treated with LPS, IFN-γ/LPS or IFN-α/LPS as positive stimuli. Of note, pre-infection of DCs with live amastigotes resulted in multiple alterations in innate signaling pathways, including degradation of STAT2, decreased phosphorylation of STAT1, 2, 3 and ERK1/2, and markedly reduced expression of interferon regulatory factor-1 (IRF-1) and IRF-8, some of which were partially reversed by pretreatment of parasites with proteasome or protease inhibitors. The impaired IL-12 production in infected DCs was not attributed to increased IL-10 production. Together, our data suggest that La parasites, especially in their intracellular forms, have evolved unique strategies to actively downregulate early innate signaling events, resulting in impaired DC function and Th1 activation.

Journal of Leukocyte Biology, 2013

Although T cell activation has been classically described to require distinct, positive stimulati... more Although T cell activation has been classically described to require distinct, positive stimulation signals that include B7-1 (CD80) and B7-2 (CD86) costimulation, overriding suppression signals that avert immune-mediated host injury are equally important. How these opposing stimulation and suppression signals work together remains incompletely defined. Our recent studies demonstrate that CD8 Teff activation in response to cognate peptide stimulation is actively suppressed by the Foxp3+ subset of CD4 cells, called Tregs. Here, we show that the elimination of Treg suppression does not bypass the requirement for positive B7-1/B7-2 costimulation. The expansion, IFN-γ cytokine production, cytolytic, and protective features of antigen-specific CD8 T cells stimulated with purified cognate peptide in Treg-ablated mice were each neutralized effectively by CTLA-4-Ig that blocks B7-1/B7-2. In turn, given the efficiency whereby CTLA-4-Ig overrides the effects of Treg ablation, the role of Foxp...

The Journal of Immunology, 2010

Type I IFNs exert diverse effector and regulatory functions in host immunity to viral and nonvira... more Type I IFNs exert diverse effector and regulatory functions in host immunity to viral and nonviral infections; however, the role of endogenous type I IFNs in leishmaniasis is unclear. We found that type I IFNR-deficient (IFNAR−/−) mice developed attenuated lesions and reduced Ag-specific immune responses following infection with Leishmania amazonensis parasites. The marked reduction in tissue parasites, even at 3 d in IFNAR−/− mice, seemed to be indicative of an enhanced innate immunity. Further mechanistic analyses indicated distinct roles for neutrophils in parasite clearance; IFNAR−/− mice displayed a rapid and sustained infiltration of neutrophils, but a limited recruitment of CD11b+Ly-6C+ inflammatory monocytes, into inflamed tissues; interactions between IFNAR−/−, but not wild-type (WT) or STAT1−/−, neutrophils and macrophages greatly enhanced parasite killing in vitro; and infected IFNAR−/− neutrophils efficiently released granular enzymes and had elevated rates of cell apopt...

The Journal of Immunology, 2010

The nature and differentiation of regulatory CD8+CD28− T cells are poorly understood. In this stu... more The nature and differentiation of regulatory CD8+CD28− T cells are poorly understood. In this study, we demonstrate that native Ag trichosanthin (Tk), a highly purified linear peptide isolated from a Chinese medicinal herb, is able to induce strong suppression of OVA-specific lymphoproliferation at low concentrations via activation of IL-4/IL-10–secreting CD8+CD28− regulatory T cells (Tregs). To elucidate the underlying mechanisms, we firstly identified two types of mouse inbred strains, high susceptible (HS) and low susceptible, for the Tk-related suppression. They are H-2d (or H-2b) and H-2k, respectively. The suppression is evoked only if bone marrow-derived dendritic cells (BDCs) instead of purified T cells are treated with Tk in an OVA-specific T-BDC interaction. Moreover, a special pattern of cytokine/transcription factors (IL-4+IL-10+IFN-γ−Gata3+T-bet−) during suppressed OVA-specific T cell proliferation was observed in HS C57BL/6 but not in low-susceptible C3H/He mice. Consi...

The Journal of Immunology, 2006

It has been demonstrated in our previous work that, in the human skin-grafting model, the express... more It has been demonstrated in our previous work that, in the human skin-grafting model, the expression of costimulatory molecule B7H1 (PD-L1) by keratinocytes plays an essential role in inducing local tolerance via activation of IL-10-secreting T cells. This study further analyzes the role of B7H1 in differentiation of type 1 T regulatory (Tr1) cells and explores underlying mechanisms. Mouse fusion protein B7H1-Ig is used, together with immobilized anti-CD3 mAb, to costimulate the purified naive CD4+ T cells. B7H1-Ig-treated CD4+ T cells were found to activate a characteristic Tr1 population possessing a CD4+CD25−Foxp3− CD45RBlow phenotype. These regulatory T cells strongly inhibited the Th1-dominated MLR by secretion of IL-10 and TGF-β. Moreover, B7H1-treated Tr1 cells also resulted in suppressed clinical scores and demyelination when adoptively transferred into mice with experimental allergic encephalomyelitis. Furthermore, analysis of the cytokine profile indicated that there were ...

The Journal of Immunology, 2008

Leishmania (Viannia) braziliensis is the causative agent of cutaneous and mucosal leishmaniasis i... more Leishmania (Viannia) braziliensis is the causative agent of cutaneous and mucosal leishmaniasis in South America, and the latter is a severe and disfiguring form of the disease. Our understanding of how L. braziliensis parasites interact with dendritic cells (DCs) is limited, partially due to the difficulty in generating axenic amastigotes. In this study, we successfully generated axenic amastigotes of L. braziliensis and used them to test the hypothesis that L. braziliensis infection efficiently triggers innate responses in DCs and the subsequent adaptive immune responses for parasite clearance. This study has revealed unique immunological features of L. braziliensis infection. Firstly, axenic amastigotes showed higher infectivity and the potential to stimulate C57BL/6 (B6) bone marrow-derived dendritic cells to produce IL-12p40 when compared with their promastigote counterparts. Both parasite-carrying and bystander DCs displayed an activated (CD11chighCD45RB−CD83+CD40+CD80+) pheno...

International Journal for Parasitology, 2008

Leishmania amazonensis infection, occurring predominantly in Central and South America, can manif... more Leishmania amazonensis infection, occurring predominantly in Central and South America, can manifest itself in several forms, including those of cutaneous and diffuse cutaneous leishmaniasis. The outcome of L. amazonensis infection depends largely on host immune responses to the parasites. While CD4 + T cell activation is a prerequisite for pathogenesis in L. amazonensis-infected mice, the roles of B cells and their antibody production are unclear. In this study, we provide evidence suggesting that B cells and antibodies are involved in disease pathogenesis. We documented a correlation between B cell activation and lesion progress in immunocompetent mice. In the absence of functional B cells and antibodies, JhD mice showed a delayed onset of disease and developed small lesions. Histological examination of these mice revealed a significant reduction in CD4 + and CD8 + T cells, but not in MAC1 + macrophages, at the infection site. In contrast to the wild-type mice that showed typical tissue necrosis, L. amazonensis-infected JhD mice showed no or minimal signs of necrotic foci. A marked reduction in CD4 + T cell proliferation and cytokine (IFN-c and IL-10) production in infected JhD mice suggested an involvement of B cells and antibodies in the priming of parasite-specific T cells. This notion was further supported by the observations that adoptive transfer of B cells or antibodies could restore CD4 + T cell activation and migration in infected JhD mice. Moreover, antibody coating of parasites could stimulate dendritic cells to produce high levels of cytokines and increase their ability to prime naïve CD4 + T cells. Since CD4 + T cells are crucial to disease pathogenesis, this study suggests that B cells and their antibody production enhanced L. amazonensis infection, partially by promoting T cell priming and cellular migration to the infection site.

Infection and Immunity, 2011

Leishmania parasites alternate between flagellated promastigotes in sand flies and nonflagellated... more Leishmania parasites alternate between flagellated promastigotes in sand flies and nonflagellated amastigotes in mammals, causing a spectrum of serious diseases. To survive, they must resist the harsh conditions in phagocytes (including acidic pH, elevated temperature, and increased oxidative/nitrosative stress) and evade the immune response. Recent studies have highlighted the importance of sphingolipid (SL) metabolism in Leishmania virulence. In particular, we have generated a Leishmania major iscl − mutant which is deficient in SL degradation but grows normally as promastigotes in culture. Importantly, iscl − mutants cannot induce pathology in either immunocompetent or immunodeficient mice yet are able to persist at low levels. In this study, we investigated how the degradation of SLs might contribute to Leishmania infection. First, unlike wild-type (WT) L. major , iscl − mutants do not trigger polarized T cell responses in mice. Second, like WT parasites, iscl − mutants possess ...

Infection and Immunity, 2009

We have previously reported that Leishmania braziliensis infection can activate murine dendritic ... more We have previously reported that Leishmania braziliensis infection can activate murine dendritic cells (DCs) and upregulate signaling pathways that are essential for the initiation of innate immunity. However, it remains unclear whether Toll-like receptors (TLRs) are involved in L. braziliensis -mediated DC activation. To address this issue, we generated bone marrow-derived DCs from MyD88 −/− and TLR2 −/− mice and examined their responsiveness to parasite infection. While wild-type DCs were efficiently activated to produce cytokines and prime naïve CD4 + T cells, L. braziliensis -infected MyD88 −/− DCs exhibited less activation and decreased production of interleukin-12 (IL-12) p40. Furthermore, MyD88 −/− mice were more susceptible to infection in that they developed larger and prolonged lesions compared to those in control mice. In sharp contrast, the lack of TLR2 resulted in an enhanced DC activation and increased IL-12 p40 production after infection. As such, L. braziliensis -in...

Infection and Immunity, 2007

Leishmania amazonensis can cause progressive disease in most inbred strains of mice. We have prev... more Leishmania amazonensis can cause progressive disease in most inbred strains of mice. We have previously reported that treatment with CXCL10 activates macrophage (MΦ) effector function(s) in parasite killing and significantly delays lesion development in susceptible C57BL/6 mice via enhanced gamma interferon (IFN-γ) and interleukin 12 (IL-12) secretion; however, the mechanism underlying this enhanced immunity against L. amazonensis infection remains largely unresolved. In this study, we utilized stationary promastigotes to infect bone marrow-derived dendritic cells (DCs) of C57BL/6 mice and assessed the activation of DC subsets and the capacity of these DC subsets to prime CD4 + T cells in vitro. We found that CXCL10 induced IL-12 p40 production but reduced IL-10 production in uninfected DCs. Yet L. amazonensis -infected DCs produced elevated levels of IL-10 despite CXCL10 treatment. Elimination of endogenous IL-10 led to increased IL-12 p40 production in DCs as well as increased pro...