Immunopathology In Mice Research Articles

Evaluating the Effects of Chronic Oral Exposure to the Food Additive Silicon Dioxide on Oral Tolerance Induction and Food Sensitivities in Mice.

The increasing prevalence of food sensitivities has been attributed to changes in gut microenvironment; however, ubiquitous environmental triggers such as inorganic nanoparticles (NPs) used as food additives have not been thoroughly investigated. We explored the impact of the NP-structured food-grade silicon dioxide () on intestinal immune response involved in oral tolerance (OT) induction and evaluated the consequences of oral chronic exposure to this food-additive using a mouse model of OT to ovalbumin (OVA) and on gluten immunopathology in mice expressing the celiac disease risk gene, HLA-DQ8. Viability, proliferation, and cytokine production of mesenteric lymph node (MLN) cells were evaluated after exposure to . C57BL/6J mice and a mouse model of OT to OVA were orally exposed to or vehicle for 60 d. Fecal lipocalin-2 (Lcn-2), anti-OVA IgG, cytokine production, and immune cell populations were analyzed. Nonobese diabetic (NOD) mice expressing HLA-DQ8 (NOD/DQ8), exposed to or vehicle, were immunized with gluten and immunopathology was investigated. MLN cells exposed to presented less proliferative T cells and lower secretion of interleukin 10 (IL-10) and transforming growth factor beta () by T regulatory and cells compared to control, two factors mediating OT. Mice given exhibited intestinal Lcn-2 level and interferon gamma () secretion, showing inflammation and less production of IL-10 and . These effects were also observed in OVA-tolerized mice exposed to , in addition to a breakdown of OT and a lower intestinal frequency of T cells. In NOD/DQ8 mice immunized with gluten, the villus-to-crypt ratio was decreased while the intraepithelial lymphocyte counts and the Th1 inflammatory response were aggravated after treatment. Our results suggest that chronic oral exposure to blocked oral tolerance induction to OVA, and worsened gluten-induced immunopathology in NOD/DQ8 mice. The results should prompt investigation on the link between exposure and food sensitivities in humans. https://doi.org/10.1289/EHP12758.

Lentinan confers protection against type 1 diabetes by inducing regulatory T cell in spontaneous non-obese diabetic mice

BackgroundLentinan (LNT) is a complex fungal component that possesses effective antitumor and immunostimulating properties. However, there is a paucity of studies regarding the effects and mechanisms of LNT on type 1 diabetes.ObjectiveIn the current study, we investigated whether an intraperitoneal injection of LNT can diminish the risk of developing type 1 diabetes (T1D) in non-obese diabetic (NOD) mice and further examined possible mechanisms of LNT’s effects. Methods: Pre-diabetic female NOD mice 8 weeks of age, NOD mice with 140–160 mg/dL, 200–230 mg/dL or 350–450 mg/dL blood glucose levels were randomly divided into two groups and intraperitoneally injected with 5 mg/kg LNT or PBS every other day. Then, blood sugar levels, pancreas slices, spleen, PnLN and pancreas cells from treatment mice were examined.ResultsOur results demonstrated that low-dosage injections (5 mg/kg) of LNT significantly suppressed immunopathology in mice with autoimmune diabetes but increased the Foxp3+ regulatory T cells (Treg cells) proportion in mice. LNT treatment induced the production of Tregs in the spleen and PnLN cells of NOD mice in vitro. Furthermore, the adoptive transfer of Treg cells extracted from LNT-treated NOD mice confirmed that LNT induced Treg function in vivo and revealed an enhanced suppressive capacity as compared to the Tregs isolated from the control group.ConclusionLNT was capable of stimulating the production of Treg cells from naive CD4 + T cells, which implies that LNT exhibits therapeutic values as a tolerogenic adjuvant and may be used to reverse hyperglycaemia in the early and late stages of T1D.

CD47 expression attenuates Ebola virus-induced immunopathology in mice

It has been shown that a very early cell-intrinsic response to infection is the upregulation of CD47 cell surface expression, a molecule known for delivering a “don't eat me signal” that inhibits macrophage-mediated phagocytosis and antigen presentation. Thus, blockade of CD47 signaling during lymphocytic choriomenigitis virus infections of mice has been shown to enhance the kinetics and potency of immune responses, thereby producing faster recovery. It seems counterintuitive that one of the earliest responses to infection would be immunoinhibitory, but it has been hypothesized that CD47 induction acts as an innate immune system checkpoint to prevent immune overactivation and immunopathogenic responses during certain infections. In the current study we examined the effect of CD47 blockade on lethal Ebola virus infection of mice. At 6 days post-infection, CD47 blockade was associated with significantly increased activation of B cells along with increases in recently cytolytic CD8+ T cells. However, the anti-CD47-treated mice exhibited increased weight loss, higher virus titers, and succumbed more rapidly. The anti-CD47-treated mice also had increased inflammatory cytokines in the plasma indicative of a “cytokine storm”. Thus, in the context of this rapid hemorrhagic disease, CD47 blockade indeed exacerbated immunopathology and disease severity.

Hepatocyte CD1d protects against liver immunopathology in mice with schistosomiasis japonica.

Schistosomiasis is a neglected tropical disease with over 250 million people infected worldwide. The main clinically important species Schistosoma mansoni (S.mansoni) and Schistosoma japonicum (S.japonicum) cause inflammatory responses against tissue-trapped eggs, resulting in formation of granulomas mainly in host liver. Persistent granulomatous response results in severe fibrosis in the liver, leading to irreversible impairment of the liver and even death of the host. CD1d, a highly conserved MHC class I-like molecule, is expressed by both haematopoietic and non-haematopoietic cells. CD1d on antigen-presenting cells (APCs) of haematopoietic origin presents pathogen-derived lipid antigens to natural killer T (NKT) cells, which enables them to rapidly produce large amounts of various cytokines and facilitate CD4+ T helper (Th) cell differentiation upon invading pathogens. Noteworthy, hepatocytes of non-haematopoietic origin have recently been shown to be involved in maintaining liver NKT cell homeostasis through a CD1d-dependent manner. However, whether hepatocyte CD1d-dependent regulation of NKT cell homeostasis also modulates CD4+ Th cell responses and liver immunopathology in murine schistosomiasis remains to be addressed. Here, we show in mice that CD1d expression on hepatocytes was decreased dramatically upon S.japonicum infection, accompanied by increased NKT cells, as well as upregulated Th1 and Th2 responses. Overexpression of CD1d in hepatocytes significantly decreased local NKT numbers and cytokines (IFN-γ, IL-4, IL-13), concomitantly with downregulation of both Th1 and Th2 responses and alleviation in pathological damage in livers of S.japonicum-infected mice. These findings highlight the potential of hepatocyte CD1d-targeted therapies for liver immunopathology control in schistosomiasis.

Loss of the disease-associated glycosyltransferase Galnt3 alters Muc10 glycosylation and the composition of the oral microbiome

Loss of the disease-associated glycosyltransferase Galnt3 alters Muc10 glycosylation and the composition of the oral microbiome

Glucagon-like peptide 1 receptor signaling attenuates respiratory syncytial virus–induced type 2 responses and immunopathology

GLP-1R signaling, an emerging anti-inflammatory therapeutic 59 target, 60 attenuated type 2-associated immunopathology in mice infected with a strain of RSV that was 61 isolated from a hospitalized infant with severe lower respiratory tract infection and bronchiolitis.

Gimap5-dependent inactivation of GSK3\u03b2 is required for CD4+ T cell homeostasis and prevention of immune pathology

GTPase of immunity-associated protein 5 (Gimap5) is linked with lymphocyte survival, autoimmunity, and colitis, but its mechanisms of action are unclear. Here, we show that Gimap5 is essential for the inactivation of glycogen synthase kinase-3β (GSK3β) following T cell activation. In the absence of Gimap5, constitutive GSK3β activity constrains c-Myc induction and NFATc1 nuclear import, thereby limiting productive CD4+ T cell proliferation. Additionally, Gimap5 facilitates Ser389 phosphorylation and nuclear translocation of GSK3β, thereby limiting DNA damage in CD4+ T cells. Importantly, pharmacological inhibition and genetic targeting of GSK3β can override Gimap5 deficiency in CD4+ T cells and ameliorates immunopathology in mice. Finally, we show that a human patient with a GIMAP5 loss-of-function mutation has lymphopenia and impaired T cell proliferation in vitro that can be rescued with GSK3 inhibitors. Given that the expression of Gimap5 is lymphocyte-restricted, we propose that its control of GSK3β is an important checkpoint in lymphocyte proliferation.

A Commensal Bifidobacterium longum Strain Prevents Gluten-Related Immunopathology in Mice through Expression of a Serine Protease Inhibitor.

Microbiota-modulating strategies, including probiotic administration, have been tested for the treatment of chronic gastrointestinal diseases despite limited information regarding their mechanisms of action. We previously demonstrated that patients with active celiac disease have decreased duodenal expression of elafin, a human serine protease inhibitor, and supplementation of elafin by a recombinant Lactococcus lactis strain prevents gliadin-induced immunopathology in the NOD/DQ8 mouse model of gluten sensitivity. The commensal probiotic strain Bifidobacterium longum NCC2705 produces a serine protease inhibitor (Srp) that exhibits immune-modulating properties. Here, we demonstrate that B. longum NCC2705, but not a srp knockout mutant, attenuates gliadin-induced immunopathology and impacts intestinal microbial composition in NOD/DQ8 mice. Our results highlight the beneficial effects of a serine protease inhibitor produced by commensal B. longum strains.IMPORTANCE Probiotic therapies have been widely used to treat gastrointestinal disorders with variable success and poor mechanistic insight. Delivery of specific anti-inflammatory molecules has been limited to the use of genetically modified organisms, which has raised some public and regulatory concerns. By examining a specific microbial product naturally expressed by a commensal bacterial strain, we provide insight into a mechanistic basis for the use of B. longum NCC2705 to help treat gluten-related disorders.

Blockade of PD-1 Signaling Enhances Th2 Cell Responses and Aggravates Liver Immunopathology in Mice with Schistosomiasis japonica.

BackgroundMore than 220 million people worldwide are chronically infected with schistosomes, causing severe disease or even death. The major pathological damage occurring in schistosomiasis is attributable to the granulomatous inflammatory response and liver fibrosis induced by schistosome eggs. The inflammatory response is tightly controlled and parallels immunosuppressive regulation, constantly maintaining immune homeostasis and limiting excessive immunopathologic damage in important host organs. It is well known that the activation of programmed death 1 (PD-1) signaling causes a significant suppression of T cell function. However, the roles of PD-1 signaling in modulating CD4+ T cell responses and immunopathology during schistosome infection, have yet to be defined.Methodology/Principal FindingsHere, we show that PD-1 is upregulated in CD4+ T cells in Schistosoma japonicum (S. japonicum)-infected patients. We also show the upregulation of PD-1 expression in CD4+ T cells in the spleens, mesenteric lymph nodes, and livers of mice with S. japonicum infection. Finally, we found that the blockade of PD-1 signaling enhanced CD4+ T helper 2 (Th2) cell responses and led to more severe liver immunopathology in mice with S. japonicum infection, without a reduction of egg production or deposition in the host liver.Conclusions/SignificanceOverall, our study suggests that PD-1 signaling is specifically induced to control Th2-associated inflammatory responses during schistosome infection and is beneficial to the development of PD-1-based control of liver immunopathology.

Ebola Virus Replication and Disease Without Immunopathology in Mice Expressing Transgenes to Support Human Myeloid and Lymphoid Cell Engraftment.

The study of Ebola virus (EBOV) pathogenesis in vivo has been limited to nonhuman primate models or use of an adapted virus to cause disease in rodent models. Herein we describe wild-type EBOV (Makona variant) infection of mice engrafted with human hematopoietic CD34+ stem cells (Hu-NSG™-SGM3 mice; hereafter referred to as SGM3 HuMice). SGM3 HuMice support increased development of myeloid immune cells, which are primary EBOV targets. In SGM3 HuMice, EBOV replicated to high levels, and disease was observed following either intraperitoneal or intramuscular inoculation. Despite the high levels of viral antigen and inflammatory cell infiltration in the liver, the characteristic histopathology of Ebola virus disease was not observed, and this absence of severe immunopathology may have contributed to the recovery and survival of some of the animals. Future investigations into the underlying mechanisms of the atypical disease presentation in SGM3 HuMice will provide additional insights into the immunopathogenesis of severe EBOV disease.

Alcohol intake alters immune responses and promotes CNS viral persistence in mice

Chronic hepatitis C virus (HCV) infection leads to progressive liver disease and is associated with a variety of extrahepatic effects, including central nervous system (CNS) damage and neuropsychiatric impairments. Alcohol abuse can exacerbate these adverse effects on brain and behavior, but the molecular mechanisms are not well understood. This study investigated the role of alcohol in regulating viral persistence and CNS immunopathology in mice infected with lymphocytic choriomeningitis virus (LCMV), a model for HCV infections in humans. Female and male BALB/c mice (n=94) were exposed to alcohol (ethanol; EtOH) and water (or water only) using a two-bottle choice paradigm, followed one week later by infection with either LCMV clone 13 (causes chronic infection similar to chronic HCV), LCMV Armstrong (causes acute infection), or vehicle. Mice were monitored for 60days post-infection and continued to receive 24-h access to EtOH and water. Animals infected with LCMV clone 13 drank more EtOH, as compared to those with an acute or no viral infection. Six weeks after infection with LCMV clone 13, mice with EtOH exposure evidenced higher serum viral titers, as compared to mice without EtOH exposure. EtOH intake was also associated with reductions in virus-specific CD8+ T cell frequencies (particularly CD11ahi subsets) and evidence of persistent CNS viremia in chronically infected mice. These findings support the hypothesis that EtOH use and chronic viral infection can result in combined toxic effects accelerating CNS damage and neuropsychiatric dysfunction and suggest that examining the role of EtOH in regulating viral persistence and CNS immunopathology in mice infected with LCMV can lead to a more comprehensive understanding of comorbid alcohol use disorder and chronic viral infection.

Polygenic mutations in the cytotoxicity pathway increase susceptibility to develop HLH immunopathology in mice

AbstractHemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory disease. Inherited forms of HLH are caused by biallelic mutations in several effectors of granule-dependent lymphocyte-mediated cytotoxicity. A small proportion of patients with a so-called “secondary” form of HLH, which develops in the aftermath of infection, autoimmunity, or cancer, carry a monoallelic mutation in one or more HLH-associated genes. Although this observation suggests that HLH may have a polygenic mode of inheritance, the latter is very difficult to prove in humans. In order to determine whether the accumulation of partial genetic defects in lymphocyte-mediated cytotoxicity can contribute to the development of HLH, we generated mice that were doubly or triply heterozygous for mutations in HLH-associated genes, those coding for perforin, Rab27a, and syntaxin-11. We found that the accumulation of monoallelic mutations did indeed increase the risk of developing HLH immunopathology after lymphocytic choriomeningitis virus infection. In mechanistic terms, the accumulation of heterozygous mutations in the two degranulation genes Rab27a and syntaxin-11, impaired the dynamics and secretion of cytotoxic granules at the immune synapse of T lymphocytes. In addition, the accumulation of heterozygous mutations within the three genes impaired natural killer lymphocyte cytotoxicity in vivo. The genetic defects can be ranked in terms of the severity of the resulting HLH manifestations. Our results form the basis of a polygenic model of the occurrence of secondary HLH.

Intestinal Microbiota Modulates Gluten-Induced Immunopathology in Humanized Mice

Celiac disease (CD) is an immune-mediated enteropathy triggered by gluten in genetically susceptible individuals. The recent increase in CD incidence suggests that additional environmental factors, such as intestinal microbiota alterations, are involved in its pathogenesis. However, there is no direct evidence of modulation of gluten-induced immunopathology by the microbiota. We investigated whether specific microbiota compositions influence immune responses to gluten in mice expressing the human DQ8 gene, which confers moderate CD genetic susceptibility. Germ-free mice, clean specific-pathogen-free (SPF) mice colonized with a microbiota devoid of opportunistic pathogens and Proteobacteria, and conventional SPF mice that harbor a complex microbiota that includes opportunistic pathogens were used. Clean SPF mice had attenuated responses to gluten compared to germ-free and conventional SPF mice. Germ-free mice developed increased intraepithelial lymphocytes, markers of intraepithelial lymphocyte cytotoxicity, gliadin-specific antibodies, and a proinflammatory gliadin-specific T-cell response. Antibiotic treatment, leading to Proteobacteria expansion, further enhanced gluten-induced immunopathology in conventional SPF mice. Protection against gluten-induced immunopathology in clean SPF mice was reversed after supplementation with a member of the Proteobacteria phylum, an enteroadherent Escherichia coli isolated from a CD patient. The intestinal microbiota can both positively and negatively modulate gluten-induced immunopathology in mice. In subjects with moderate genetic susceptibility, intestinal microbiota changes may be a factor that increases CD risk.

Heat Shock Protein 60 in Eggs Specifically Induces Tregs and Reduces Liver Immunopathology in Mice with Schistosomiasis Japonica.

BackgroundParasitic helminths need to suppress the host immune system to establish chronic infections. Paradoxically, immunosuppression induced by the worm also benefits the host by limiting excessive inflammation and tissue damage, which remains the major cause leading to serious morbidity and mortality. Regulatory T cells (Tregs) are key immune regulators of this mutualism. The successive rise in Tregs during schistosome infection plays a critical role in immunoregulation. We and others previously showed that Schistosoma japonicum (S. japonicum) egg antigens (SEA) induce Tregs both in vitro and in vivo. In addition, we identified that SjHSP60 derived from SEA significantly induces Tregs in vivo and in vitro. However, the contribution of SjHSP60 in SEA to Treg induction and the related mechanisms of the Treg induction have not yet been identified.Methodology/Principal FindingsIn this study, we showed that S. japonicum stress protein HSP60 (SjHSP60) was constitutively and extensively expressed in eggs of S. japonicum. SjHSP60 specially induced Tregs in vivo and in vitro without inducing other CD4+ T sub-populations including Th1, Th2 and Th17 cells. Furthermore, we showed that the SjHSP60-depleted SEA almost lost the ability in vitro and displayed a significant impaired ability to induce Tregs in vivo. Finally, our study illustrated that the mechanisms of SjHSP60-mediated induction of Tregs are through both conversion of CD4+CD25- T cells into CD4+CD25+Foxp3+ Tregs and expansion of preexisting CD4+CD25+Foxp3+ Tregs in a TLR4-dependent manner.Conclusions/SignificanceCollectively, our findings identify SjHSP60 as a major parasitic contributor of Treg induction in S. japonicum egg antigens, which not only contributes to the better understanding of the mechanism of immunoregulation during helminth infection, but also suggests its potential as a therapeutic target for control of immunopathology, allergic and autoimmune diseases.

Lactobacilus johnsonii supplemented mice modulate RSV-induced disease and is associated with increased DHA metabolite that alters DC activation through PPAR- γ. (VIR9P.1148)

Abstract The gut microbiome contributes to a variety of mammalian processes, including modulation of host immune responses. We have found that L. johnsonii-supplemented mice displayed altered gut microbiome profiles and reduced RSV-induced pulmonary immunopathology. Metabolomics analysis of plasma from L. johnsonii-supplemented mice identified docosahexaenoic acid (DHA) and 2-hydroxyisobutyrate (butyrate precursor) as increased metabolites. We hypothesized that DHA and butyrate played a role in the modulation of the immune response in lung. We found that bone marrow-derived dendritic cells (BMDC) treated with DHA or butyrate expressed and produced reduced levels of IL-12, IL-6, IL-1β, IFN-β and TNF-α when stimulated with LPS, CpG or RSV compared to untreated cells. DHA treatment of RSV-infected BMDC prior to their co-culture with T cells isolated from RSV-infected mice significantly reduced their production of Th2 cytokines and IFNΥ. Then, we determined whether DHA was activating the nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR-γ) in BMDC, which has been described as an inflammatory response inhibitor. We observed that BMDC treated with DHA and PPAR- γ antagonist (GW9662), had altered expression of mRNA and production of cytokines compared to DHA treated cells. These results suggest that DHA is modulating the immune response through PPAR-γ in dendritic cells and may be one mechanism of attenuating RSV immunopathology in mice supplemented with L. johnsonii.

A novel immunoregulatory role for NK-cell cytotoxicity in protection from HLH-like immunopathology in mice

AbstractThe impairment of cytotoxic activity of lymphocytes disturbs immune surveillance and leads to the development of hemophagocytic lymphohistiocytic syndrome (HLH). Although cytotoxic T lymphocyte (CTL) control of HLH development is well documented, the role for natural killer (NK)-cell effector functions in the pathogenesis of this immune disorder remains unclear. In this study, we specifically targeted a defect in cytotoxicity to either CTL or NK cells in mice so as to dissect the contribution of these lymphocyte subsets to HLH-like disease severity after lymphocytic choriomeningitis virus (LCMV) infection. We found that NK-cell cytotoxicity was sufficient to protect mice from the fatal outcome that characterizes HLH-like disease and was also sufficient to reduce HLH-like manifestations. Mechanistically, NK-cell cytotoxicity reduced tissue infiltration by inflammatory macrophages and downmodulated LCMV-specific T-cell responses by limiting hyperactivation of CTL. Interestingly, the critical protective effect of NK cells on HLH was independent of interferon-γ secretion and changes in viral load. Therefore our findings identify a crucial role of NK-cell cytotoxicity in limiting HLH-like immunopathology, highlighting the important role of NK cytotoxic activity in immune homeostasis.

Sialic acid binding preference of influenza A viruses regulates pathological leukocyte recruitment (VIR2P.1012)

Abstract Influenza A virus (IAV), a seasonal respiratory pathogen, has a high capacity to cause pandemic infections resulting in severe lung pathology. Multiple studies using pathological IAV strains have demonstrated the importance of macrophages and neutrophils, but whether the pathological inflammation induced by different IAV isolates is identical has not been directly compared. Here we demonstrate that while both A/WSN/33 (WSN) and A/PR/8/34 (PR8) influenza viruses cause significant immunopathology in mice the inflammatory milieu differs between the two isolates. Specifically, PR8 infection was associated with greater neutrophil recruitment and CCL4 and CXCL2 expression; in contrast, WSN infection was associated mast cell activation, recruitment of a unique Ly6ghigh Ly6chigh monocyte population, and elevated levels of IFNα, G-CSF, and CCL2. One difference between WSN and PR8 is their hemaggultinin molecules preferentially bind to α2,6- and α2,3-linked sialic acids, respectively. Using a recombinant WSN strain whose sialic acid binding preference is switched to α2,3-linkages, we observed minimal mast cell activation and a switch to a more neutrophilic inflammation. Thus, sialic acid binding preference of IAV isolates has clinically important alterations to the inflammatory cascade(s) activated. These findings have important implications for our ability to therapeutically target the host inflammatory response to limit morbidity following influenza virus infection

In vitro and in vivo pharmacological assessment of a targeted plasmid gene containing immunotoxin, DT390-IL-18-SRα on suppression of immunopathology in mice experimentally infected with Shistosoma mansoni (P4192)

Abstract Purpose: To evaluate both in vitro and in vivo effects of DT390-IL-18-SRα immunotoxoin on the development of liver immunopathology in murine schistosomiasis mansoni. Methods: The antiproliferative effect and in vitro granuloma formation (IVGF) inhibition were evaluated using methyl thaiazolyl tetrazolium and IVGF index respectively. In vivo evaluation, mice were divided into four groups of twelve mice each: Group1 normal non infected (-ve control), Group 2, 3 and 4 were infected percutaneously with 25 cercariae. After 6 weeks post infection, Group2 was treated with PBS (+ve control), Group3 was treated with plasmid DNA (50 µg) embedded with cationic liposome in 50 µl PBS, injected intramuscular in the hind limbs once daily for two weeks and Group4 was treated with DT390-SRα (mutant control). After animals sacrification, liver was removed for histopathological studies. Results: DT390-IL-18-SRα showed suppression of spleen lymphocytes proliferation and IVGF in a dose dependant manner as well as suppression of liver granulomas size by 80%, while mutant toxin had no significant suppression. Conclusion: The immunotoxin showed selective toxicity to antigen activated lymphocytes in vitro with reduced clinical and pathological severities of the disease.

Δ9-Tetrahydrocannabinol Impairs the Inflammatory Response to Influenza Infection: Role of Antigen-Presenting Cells and the Cannabinoid Receptors 1 and 2

Δ(9)-tetrahydrocannabinol (Δ(9)-THC) has potent immune modulatory properties and can impair pathogen-induced immune defenses, which in part have been attributed to ligation of the cannabinoid receptors 1 (CB(1)) and 2 (CB(2)). Most recently, dendritic cells (DC) were identified for their potential to enhance influenza-induced immunopathology in mice lacking CB(1) and CB(2) (CB(1) (-/-)CB(2) (-/-)). This study focused on the modulation of the inflammatory immune response to influenza by Δ(9)-THC and the role of CB(1) and/or CB(2) as receptor targets for Δ(9)-THC. C57Bl/6 (wild type) and CB(1) (-/-)CB(2) (-/-) mice were administered Δ(9)-THC (75 mg/kg) surrounding the intranasal instillation of A/PR/8/34 influenza virus. Three days post infection (dpi), Δ(9)-THC broadly decreased expression levels of mRNA induced by the innate immune response to influenza, suppressed the percentage of interferon-gamma (IFN-γ)-producing CD4(+) and interleukin-17-producing NK1.1(+) cells, and reduced the influx of antigen-presenting cells (APC), including inflammatory myeloid cells and monocytes/macrophages, into the lung in a CB(1)- and/or CB(2)-dependent manner. Δ(9)-THC had little effect on the expression of CD86, major histocompatibility complex I (MHC I), and MHC II by APC isolated from the lung. In vitro studies demonstrated that lipopolysaccharide (LPS)-induced maturation was suppressed by Δ(9)-THC in bone marrow-derived DC (bmDC). Furthermore, antigen-specific IFN-γ production by CD8(+) T cells after coculture was reduced by Δ(9)-THC treatment of bmDC in a CB(1)- and/or CB(2)-dependent manner. Collectively, these studies suggest that Δ(9)-THC potently suppresses myeloid cell immune function, in a manner involving CB(1) and/or CB(2), thereby impairing immune responses to influenza infection.

Neutrophils Suppresses Protective Immunity and Mediates Immunopathology in Mice during Fatal Bacterial Infection-Induced Toxic Shock (67.1)

Abstract Ehrlichia chaffeensis is an obligate intracellular bacteria that causes systemic infection and fatal toxic shock-like syndrome in immunocompetent patients. The balance between protective immunity mediated by CD4+Th1 cells, and immunopathology, which is mediated by NK and CD8+T cells, determines the outcome of Ehrlichia infection in mice. Early recruitment of neutrophils to the sites of infection is critical for the control of bacterial infection. However, the contribution of neutrophils to protective immunity or immunopathology during Ehrlichia infection remains undefined. Compared to innocuous ehrlichial infection, lethal high-dose Ehrlichia infection of wild type mice is associated with a substantial expansion of activated neutrophils at the main sites of infection and a substantial TLR2 signaling. Surprisingly, depletion of neutrophils from lethally-infected mice enhanced bacterial elimination, decreased immune -mediated pathology, and prolonged survival. Furthermore, neutrophil depletion in infected mice resulted in amelioration of pathogenic responses as evidenced by abrogation of cytokine and chemokine storm and decreased frequency of pathogenic TNF-alpha- producing CD8+T cells compared to lethally infected isotype controls. These results revealed an unexpected role of neutrophils in suppression of protective immunity and mediating immunopathology during infection with intracellular bacteria.