Highly biased type 1 immune responses in mice deficient in LFA-1 in Listeria monocytogenes infection are caused by elevated IL-12 production by granulocytes

LFA-1 (CD11a/CD18) plays a key role in various inflammatory responses. Here we show that the acquired immune response to Listeria monocytogenes is highly biased toward type 1 in the absence of LFA-1. At the early stage of listeriosis, numbers of IFN-gamma producers in the liver and spleen of LFA-1(-/-) mice were markedly increased compared with heterozygous littermates and Valpha14(+)NKT cell-deficient mice, and NK cells were major IFN-gamma producers. Numbers of IL-12 producers were also markedly elevated in LFA-1(-/-) mice compared with heterozygous littermates, and endogenous IL-12 neutralization impaired IFN-gamma production by NK cells. Granulocyte depletion diminished numbers of IL-12 producers and IFN-gamma-secreting NK cells in the liver of LFA-1(-/-) mice. Granulocytes from the liver of L. monocytogenes-infected LFA-1(-/-) mice were potent IL-12 producers. Thus, in the absence of LFA-1, granulocytes are a major source of IL-12 at the early stage of listeriosis. We assume that highly biased type 1 immune responses in LFA-1(-/-) mice are caused by increased levels of IL-12 from granulocytes and that granulocytes play a major role in IFN-gamma secretion by NK cells. In conclusion, LFA-1 regulates type 1 immune responses by controlling prompt infiltration of IL-12-producing granulocytes into sites of inflammation.     

Increased resistance of LFA-1-deficient mice to lipopolysaccharide-induced shock/liver injury in the presence of TNF-alpha and IL-12 is mediated by IL-10: a novel role for LFA-1 in the regulation of the proinflammatory and anti-inflammatory cytokine balance

Challenge with low doses of LPS together with D-galactosamine causes severe liver injury, resulting in lethal shock (low dose LPS-induced shock). We examined the role of LFA-1 in low dose LPS-induced shock. LFA-1(-/-) mice were more resistant to low dose LPS-induced shock/liver injury than their heterozygous littermates, although serum levels of TNF-alpha and IL-12 were higher in these mice. C57BL/6 mice were not rescued from lethal effects of LPS by depletion of NK1(+) cells, granulocytes, or macrophages, and susceptibility of NKT cell-deficient mice was comparable to that of controls. High numbers of platelets were detected in the liver of LFA-1(+/-) mice after low dose LPS challenge, whereas liver accumulation of platelets was only marginal in LFA-1(-/-) mice. Following low dose LPS challenge, serum levels of IL-10 were higher in LFA-1(-/-) mice than in LFA-1(+/-) mice, and susceptibility to low dose LPS-induced shock as well as platelet accumulation in the liver of LFA-1(-/-) mice were markedly increased by IL-10 neutralization. Serum levels of IL-10 in LFA-1(+/-) mice were only marginally affected by macrophage depletion. However, in LFA-1(-/-) mice macrophage depletion markedly reduced serum levels of IL-10, and as a corollary, susceptibility of LFA-1(-/-) mice to low dose LPS-induced shock was markedly elevated despite the fact that TNF-alpha levels were also diminished. We conclude that LFA-1 participates in LPS-induced lethal shock/liver injury by regulating IL-10 secretion from macrophages and that IL-10 plays a decisive role in resistance to shock/liver injury. Our data point to a novel role of LFA-1 in control of the proinflammatory/anti-inflammatory cytokine network.     

The aryl hydrocarbon receptor is required for optimal resistance to Listeria monocytogenes infection in mice

The aryl hydrocarbon receptor (AhR) is part of a powerful signaling system that is triggered by xenobiotic agents such as polychlorinated hydrocarbons and polycyclic aromatic hydrocarbons. Although activation of the AhR by 2,3,7,8-tetrachlorodibenzo-p-dioxin or certain polycyclic aromatic hydrocarbons can lead to immunosuppression, there is also increasing evidence that the AhR regulates certain normal developmental processes. In this study, we asked whether the AhR plays a role in host resistance using murine listeriosis as an experimental system. Our data clearly demonstrate that AhR null C57BL/6J mice (AhR(-/-)) are more susceptible to listeriosis than AhR heterozygous (AhR(+/-)) littermates when inoculated i.v. with log-phase Listeria monocytogenes. AhR(-/-) mice exhibited greater numbers of CFU of L. monocytogenes in the spleen and liver, and greater histopathological changes in the liver than AhR(+/-) mice. Serum levels of IL-6, MCP-1, IFN-gamma, and TNF-alpha were comparable between L. monocytogenes-infected AhR(-/-) and AhR(+/-) mice. Increased levels of IL-12 and IL-10 were observed in L. monocytogenes-infected AhR(-/-) mice. No significant difference was found between AhR(+/-) and AhR(-/-) macrophages ex vivo with regard to their ability to ingest and inhibit intracellular growth of L. monocytogenes. Intracellular cytokine staining of CD4(+) and CD8(+) splenocytes for IFN-gamma and TNF-alpha revealed comparable T cell-mediated responses in AhR(-/-) and AhR(+/-) mice. Previously infected AhR(-/-) and AhR(+/-) mice both exhibited enhanced resistance to reinfection with L. monocytogenes. These data provide the first evidence that AhR is required for optimal resistance but is not essential for adaptive immune response to L. monocytogenes infection.     

Role of interleukin-12 in determining differential kinetics of invariant natural killer T cells in response to differential burden of Listeria monocytogenes

Invariant (i) natural killer (NK) T cells are unique T lymphocytes expressing NKR-P1B/C (NK1.1), which recognize glycolipids, notably alpha-galactosylceramide (alpha-GalCer) presented by CD1d. The characteristic phenotype of these iNKT cells undergoes dramatic changes following Listeria monocytogenes infection, and interleukin (IL)-12 is involved in these alterations. Here we show that liver iNKT cells in mice are differentially influenced by the load of infection. Liver alpha-GalCer/CD1d tetramer-reactive (alpha-GalCer/CD1d(+)) T cells expressing NK1.1 became undetectable by day 2 following L. monocytogenes infection and concomitantly cells lacking NK1.1 increased regardless of the severity of infection. Whereas alpha-GalCer/CD1d(+)NK1.1(+) T cells remained virtually undetectable on day 4 following low-dose infection, considerable numbers of these cells were detected in high-dose-infected mice. Whereas numbers of IL-12 producers in the liver on day 4 post infection were comparable in low- and high-dose-infected mice without in vitro restimulation with heat-killed Listeria, those were more prominent in low-dose-infected mice than in high-dose-infected mice after restimulation despite the fact that higher numbers of macrophages and granulocytes infiltrated the liver in high-dose-infected mice than in low-dose-infected mice. Our results indicate that NK1.1 surface expression on iNKT cells is differentially modulated by the burden of infection, and suggest that a high bacterial load probably causes loss of IL-12 production.     

Requirement of endogenous stem cell factor and granulocyte-colony-stimulating factor for IL-17-mediated granulopoiesis

IL-17 is a novel, CD4+ T cell-restricted cytokine. In vivo, it stimulates hematopoiesis and causes neutrophilia consisting of mature granulocytes. In this study, we show that IL-17-mediated granulopoiesis requires G-CSF release and the presence or induction of the transmembrane form of stem cell factor (SCF) for optimal granulopoiesis. However, IL-17 also protects mice from G-CSF neutralization-induced neutropenia. G-CSF neutralization completely reversed IL-17-induced BM progenitor expansion, whereas splenic CFU-GM/CFU-granulocyte-erythrocyte-megakaryocyte-monocyte was only reduced by 50% in both Sl/Sld and littermate control mice. Thus, there remained a significant SCF/G-CSF-independent effect of IL-17 on splenic granulopoiesis, resulting in a preservation of mature circulating granulocytes. IL-17 is a cytokine that potentially interconnects lymphocytic and myeloid host defense and may have potential for therapeutic development.     

Overexpression of IL-15 in vivo increases antigen-driven memory CD8+ T cells following a microbe exposure.

To elucidate potential roles of IL-15 in the maintenance of memory CD8+ T cells, we followed the fate of Ag-specific CD8+ T cells directly visualized with MHC class I tetramers coupled with listeriolysin O (LLO)(91-99) in IL-15 transgenic (Tg) mice after Listeria monocytogenes infection. The numbers of LLO(91-99)-positive memory CD8+ T cells were significantly higher at 3 and 6 wk after infection than those in non-Tg mice. The LLO(91-99)-positive CD8+ T cells produced IFN-gamma in response to LLO(91-99), and an adoptive transfer of CD8+ T cells from IL-15 Tg mice infected with L. monocytogenes conferred a higher level of resistance against L. monocytogenes in normal mice. The CD44+ CD8+ T cells from infected IL-15 Tg mice expressed the higher level of Bcl-2. Transferred CD44+ CD8+ T cells divided more vigorously in naive IL-15 Tg mice than in non-Tg mice. These results suggest that IL-15 plays an important role in long-term maintenance of Ag-specific memory CD8+ T cells following microbial exposure via promotion of cell survival and homeostatic proliferation.     

IL-17A inhibits the expansion of IL-17A-producing T cells in mice through "short-loop" inhibition via IL-17 receptor

IL-23 and IL-17A regulate granulopoiesis through G-CSF, the main granulopoietic cytokine. IL-23 is secreted by activated macrophages and dendritic cells and promotes the expansion of three subsets of IL-17A-expressing neutrophil-regulatory T (Tn) cells; CD4(-)CD8(-)alphabeta(low), CD4(+)CD8(-)alphabeta(+) (Th17), and gammadelta(+) T cells. In this study, we investigate the effects of IL-17A on circulating neutrophil levels using IL-17R-deficient (Il17ra(-/-)) mice and Il17ra(-/-)Itgb2(-/-) mice that lack both IL-17R and all four beta(2) integrins. IL-17R deficiency conferred a reduction in neutrophil numbers and G-CSF levels, as did Ab blockade against IL-17A in wild-type mice. Bone marrow transplantation revealed that IL-17R expression on nonhemopoietic cells had the greatest effects on regulating blood neutrophil counts. Although circulating neutrophil numbers were reduced, IL-17A expression, secretion, and the number of IL-17A-producing Tn cells were elevated in Il17ra(-/-) and Il17ra(-/-)Itgb2(-/-) mice, suggesting a negative feedback effect through IL-17R. The negative regulation of IL-17A-producing T cells and IL-17A and IL-17F gene expression through the interactions of IL-17A or IL-17F with IL-17R was confirmed in splenocyte cultures in vitro. We conclude that IL-17A regulates blood neutrophil counts by inducing G-CSF production mainly in nonhemopoietic cells. IL-17A controls the expansion of IL-17A-producing Tn cell populations through IL-17R.     

Cutting edge: LFA-1 is required for liver NK1.1+TCR alpha beta+ cell development: evidence that liver NK1.1+TCR alpha beta+ cells originate from multiple pathways

Using mice deficient for LFA-1, CD44, and ICAM-1, we examined the role of these adhesion molecules in NK1.1+TCR alpha beta+ (NKT) cell development. Although no defect in NKT cell development was observed in CD44-/- and ICAM-1-/- mice, a dramatic reduction of liver NKT cells was observed in LFA-1-/- mice. Normal numbers of NKT cells were present in other lymphoid organs in LFA-1-/- mice. When LFA-1-/- splenocytes were injected i.v. into wild-type mice, the frequency of NKT cells among donor-derived cells in the recipient liver was normal. In contrast, when LFA-1-/- bone marrow (BM) cells were injected i.v. into irradiated wild-type mice, the frequency of liver NKT cells was significantly lower than that of mice injected with wild-type BM cells. Collectively, these data indicate that LFA-1 is required for the development of liver NKT cells, rather than the migration to and/or subsequent establishment of mature NKT cells in the liver.     

Pulmonary inflammation induced by subacute ozone is augmented in adiponectin-deficient mice: role of IL-17A

Pulmonary responses to ozone, a common air pollutant, are augmented in obese individuals. Adiponectin, an adipose-derived hormone that declines in obesity, has regulatory effects on the immune system. To determine the role of adiponectin in the pulmonary inflammation induced by extended (48-72 h) low-dose (0.3 parts per million) exposure to ozone, adiponectin-deficient (Adipo(-/-)) and wild-type mice were exposed to ozone or to room air. In wild-type mice, ozone exposure increased total bronchoalveolar lavage (BAL) adiponectin. Ozone-induced lung inflammation, including increases in BAL neutrophils, protein (an index of lung injury), IL-6, keratinocyte-derived chemokine, LPS-induced CXC chemokine, and G-CSF were augmented in Adipo(-/-) versus wild-type mice. Ozone also increased IL-17A mRNA expression to a greater extent in Adipo(-/-) versus wild-type mice. Moreover, compared with control Ab, anti-IL-17A Ab attenuated ozone-induced increases in BAL neutrophils and G-CSF in Adipo(-/-) but not in wild-type mice, suggesting that IL-17A, by promoting G-CSF release, contributed to augmented neutrophilia in Adipo(-/-) mice. Flow cytometric analysis of lung cells revealed that the number of CD45(+)/F4/80(+)/IL-17A(+) macrophages and γδ T cells expressing IL-17A increased after ozone exposure in wild-type mice and further increased in Adipo(-/-) mice. The IL-17(+) macrophages were CD11c(-) (interstitial macrophages), whereas CD11c(+) macrophages (alveolar macrophages) did not express IL-17A. Taken together, the data are consistent with the hypothesis that adiponectin protects against neutrophil recruitment induced by extended low-dose ozone exposure by inhibiting the induction and/or recruitment of IL-17A in interstitial macrophages and/or γδ T cells.     

Effects of murine recombinant interleukin 1 alpha on the host response to bacterial infection

The effects of exogenously administered rIL-1 alpha on elimination of viable listeriae from the liver and spleen during the course of a primary Listeria monocytogenes infection was studied. Similar numbers of L. monocytogenes were recovered from rIL-1 alpha-treated and control mice at up to 24 h after infection; however, by 48 h after infection more than 1 log10 fewer viable L. monocytogenes were recovered from the spleens of rIL-1 alpha-treated mice than from Listeria-infected controls. The difference in bacterial burden between IL-1 alpha-treated and control mice increased with time; by 7 days after infection viable L. monocytogenes had been eliminated from most rIL-1 alpha-treated mice, whereas control mice still harbored 10(4) to 10(5) L. monocytogenes per spleen and liver. Histopathologic examination confirmed that rIL-1 alpha-treated mice suffered considerably less damage to the spleen, liver, lung, and brain than did control mice. To determine whether rIL-1 alpha-mediated protection indirectly by augmenting the release of other cytokines, we determined serum levels of colony-stimulating activity and IFN activity in rIL-1 alpha-treated and control Listeria-infected mice. Treatment with rIL-alpha elicited an early burst of serum colony-stimulating activity as compared with sera from Listeria-infected control mice. These data suggest that exogenous administration of rIL-1 initiates release of colony-stimulating activity, and perhaps other cytokines, that accelerate the protective response of the infected host. Prophylactic augmentation of antimicrobial resistance by administration of rIL-1 alpha may be worthy of further evaluation.     

IL-17A-producing gammadeltaT cells promote CTL responses against Listeria monocytogenes infection by enhancing dendritic cell cross-presentation

Interleukin-17A-producing T cells, especially Th17, have been shown to be involved in inflammatory autoimmune diseases and host defense against extracellular infections. However, whether and how IL-17A or IL-17A-producing cells can help protection against intracellular bacteria remains controversial, especially how it regulates the adaptive immunity besides recruitment of neutrophils in the innate immune system. By infecting IL-17A-deficient mice with Listeria monocytogenes, we show in this study that IL-17A is required for the generation of Ag-specific CD8(+) CTL response against primary infection, but not for the generation of memory CD8(+) T cells against secondary challenge. Interestingly, we identify γδT cells, but not conventional CD4(+) Th17 cells, as the main cells for innate IL-17A production during L. monocytogenes infection. Furthermore, γδT cells are found to promote Ag-specific CD8(+) T cell proliferation by enhancing cross-presentation of dendritic cells through IL-17A. Adoptive transfer of Il17a(+/+) γδT cells, but not Il17a(-/-) γδT cells or Il17a(+/+) CD4(+) T cells, were sufficient to recover dendritic cells cross-presentation and defective CD8(+) T cell response in Il17a(-/-) mice. Our findings indicate an important role of infection-inducible IL-17A-producing γδT cells and their derived IL-17A against intracellular bacterial infection, providing a mechanism of IL-17A for regulation of innate and adaptive immunity.     

IL-23 is required for neutrophil homeostasis in normal and neutrophilic mice

IL-23 is secreted by macrophages and dendritic cells in response to microbial products and inflammatory cytokines. IL-23 is a heterodimer composed of the unique IL-23p19 subunit linked to the common p40 subunit that it shares with IL-12. IL-23 is implicated in autoimmune diseases, where it supports the expansion of IL-17A-producing CD4+ Th17 cells. IL-23 also regulates granulopoiesis in a neutrostat regulatory feedback loop through IL-17A-producing neutrophil regulatory (Tn) cells, most of which express gammadelta TCR. This homeostatic system is disrupted in mice lacking adhesion molecules like beta2-integrins (Itgb2-/-) which have defective neutrophil trafficking and neutrophilia. To test the role of IL-23 in the homeostatic regulation of circulating neutrophil numbers, we measured blood neutrophil numbers in p40-deficient (IL12b-/-) mice and found them reduced compared with wild-type mice. IL12b-/-Itgb2-/- mice, lacking beta2-integrins, IL-12, and IL-23 showed significantly blunted neutrophilia compared with Itgb2-/- mice. Treatment of both IL12b-/- and IL12b-/-Itgb2-/- mice with IL-23, but not IL-12, restored circulating neutrophil counts. Serum levels of IL-17A were readily detectable in Itgb2-/- mice, but not in IL12b-/-Itgb2-/- mice, suggesting that IL-17A production is reduced when IL-23 is absent. Similarly, tissue mRNA expression of IL-17A was reduced in IL12b-/-Itgb2-/-mice compared with Itgb2-/- controls. The total number of CD3+ IL-17A-producing Tn cells were significantly reduced in the spleen and lamina propria of IL12b-/-Itgb2-/- mice, with the largest reduction found in gammadelta+ T cells. Our results suggest a prominent role of IL-23 in the regulation of granulopoiesis and the prevalence of IL-17A-producing Tn cells.     

Roles of endogenous cytokines in liver apoptosis of mice in lethal Listeria monocytogenes infection

Various bacterial pathogens have been identified as mediators of apoptosis. Apoptosis reportedly shows both detrimental and beneficial effects on biological functions. We studied the role of liver apoptosis in lethal Listeria monocytogenes infection and the regulation of apoptosis by endogenous cytokines during infection. Apoptosis was observed in the spleen but not in the liver of infected mice, whereas the induction of liver necrosis was evident by rising levels of serum aminotransferases in these animals. Apoptosis was detected in the liver of L. monocytogenes-infected mice which had been treated with monoclonal antibody (mAb) against tumor necrosis factor-alpha (TNF-alpha) or interleukin-6 (IL-6), or in TNF-alpha(-/-) mice, but not in gamma- interferon (IFN-gamma)(-/-) mice or mice which had been treated with mAb against IL-4 or IL-10. Augmentation of liver apoptosis in mice treated with mAb against TNF-alpha or IL-6 or in TNF-alpha(-/-) mice correlated with the increase in bacterial numbers in the organ, while no augmentation of apoptosis was observed in the liver of IFN-gamma(-/-) mice irrespective of the marked increase in bacterial numbers in the organs, indicating that augmentation of liver apoptosis may not be merely due to the increase in bacterial growth in the organs. These results suggest that TNF-alpha and IL-6 may play an important role in protecting the liver from apoptosis in lethal L. monocytogenes infection.     

Forced expression of murine IL-17E induces growth retardation, jaundice, a Th2-biased response, and multiorgan inflammation in mice.

IL-17 is a proinflammatory cytokine, and its in vivo expression induces neutrophilia in mice. IL-17E is a recently described member of an emerging family of IL-17-related cytokines. IL-17E has been shown to bind IL-17Rh1, a protein distantly related to the IL-17R, suggesting that IL-17E probably possesses unique biological functions. In this study, we have identified the murine ortholog of IL-17E and developed transgenic mice to characterize its actions in vivo. Biological consequences of overexpression of murine (m)IL-17E, both unique to IL-17E and similar to IL-17, were revealed. Exposure to mIL-17E resulted in a Th2-biased response, characterized by eosinophilia, increased serum IgE and IgG1, and a Th2 cytokine profile including elevated serum levels of IL-13 and IL-5 and elevated gene expression of IL-4, IL-5, IL-10, and IL-13 was observed in many tissues. Increased gene expression of IFN-gamma in several tissues and elevated serum TNF-alpha were also noted. In addition, IL-17E induces G-CSF production in vitro and mIL-17E-transgenic mice had increased serum G-CSF and exhibit neutrophilia, a property shared by IL-17. Moreover, exposure to mIL-17E elicited pathological changes in multiple tissues, particularly liver, heart, and lungs, characterized by mixed inflammatory cell infiltration, epithelial hyperplasia, and hypertrophy. Taken together, these findings suggest that IL-17E is a unique pleiotropic cytokine and may be an important mediator of inflammatory and immune responses.     

TRANCE-RANK costimulation is required for IL-12 production and the initiation of a Th1-type response to Leishmania major infection in CD40L-deficient mice

Blockade of TNF-related activation-induced cytokine (TRANCE)-receptor activator of NF-kappaB (RANK) interaction reverses healing in CD40L(-/-) mice infected with Leishmania major. Although previous studies demonstrated a requirement for CD40-CD40L interaction in production of IL-12 and the development of resistance to Leishmania infection, we recently showed that CD40L(-/-) mice control infection when inoculated with low numbers of parasites and that cells from these mice produce IL-12. Here, we show that in vivo treatment with a TRANCE receptor fusion protein results in a decrease in numbers of IL-12 producing cells as well as a shift from a dominant Th1 to Th2 type response in infected mice. These results demonstrate that CD40L(-/-) mice use the TRANCE-RANK costimulatory pathway to promote IL-12 production and the activation of a protective Th1 type response.     

ATP binding cassette transporter G1 deletion induces IL-17-dependent dysregulation of pulmonary adaptive immunity

Mice with genetic deletion of the cholesterol transporter ATP binding cassette G1 (ABCG1) have pulmonary lipidosis and enhanced innate immune responses in the airway. Whether ABCG1 regulates adaptive immune responses to the environment is unknown. To this end, Abcg1(+/+) and Abcg1(-/-) mice were sensitized to OVA via the airway using low-dose LPS as an adjuvant, and then challenged with OVA aerosol. Naive Abcg1(-/-) mice displayed increased B cells, CD4(+) T cells, CD8(+) T cells, and dendritic cells (DCs) in lung and lung-draining mediastinal lymph nodes, with lung CD11b(+) DCs displaying increased CD80 and CD86. Upon allergen sensitization and challenge, the Abcg1(-/-) airway, compared with Abcg1(+/+), displayed reduced Th2 responses (IL-4, IL-5, eosinophils), increased neutrophils and IL-17, but equivalent airway hyperresponsiveness. Reduced Th2 responses were also found using standard i.p. OVA sensitization with aluminum hydroxide adjuvant. Mediastinal lymph nodes from airway-sensitized Abcg1(-/-) mice produced reduced IL-5 upon ex vivo OVA challenge. Abcg1(-/-) CD4(+) T cells displayed normal ex vivo differentiation, whereas Abcg1(-/-) DCs were found paradoxically to promote Th2 polarization. Th17 cells, IL-17(+) γδT cells, and IL-17(+) neutrophils were all increased in Abcg1(-/-) lungs, suggesting Th17 and non-Th17 sources of IL-17 excess. Neutralization of IL-17 prior to challenge normalized eosinophils and reduced neutrophilia in the Abcg1(-/-) airway. We conclude that Abcg1(-/-) mice display IL-17-mediated suppression of eosinophilia and enhancement of neutrophilia in the airway following allergen sensitization and challenge. These findings identify ABCG1 as a novel integrator of cholesterol homeostasis and adaptive immune programs.     

Differences in interleukin-12 and -15 production by dendritic cells at the early stage of Listeria monocytogenes infection between BALB/c and C57 BL/6 mice

The mechanisms responsible for the resistance of C57BL/6 mice and for the susceptibility of BALB/c mice to infection with Listeria monocytogenes were studied by comparing early IL-12 and IL-15 production by dendritic cells (DC) after infection with L. monocytogenes. Splenic DC expressing CD11b(low) and CD11c(+) obtained from C57BL/6 mice at 3 and 6 h after L. monocytogenes infection expressed higher levels of IL-12 p40 mRNA and IL-12 p40 protein than did those from BALB/c mice. Concurrently, a larger amount of IFN-gamma was produced by the splenic T cells from C57BL/6 mice in response to immobilized anti-TCRalphabeta mAb than by those from BALB/c mice, while the splenic T cells from BALB/c mice produced a higher level of IL-4 upon TCR alphabeta stimulation than did those of C57BL/6 mice. IL-15 mRNA and intracellular IL-15 protein were detected more abundantly in the DC from C57BL/6 mice than in those from BALB/c mice on day 3 after infection. CD3(+) IL2Rbeta (+) cells in the spleen were increased in C57BL/6 mice but not in BALB/c mice at the early stage after infection. Furthermore, IL-12Rbeta2 gene expression was up-regulated in T cells from C57BL/6 mice but not in those from BALB/c mice at the early stage after listerial infection. These results suggest that the difference in early production of IL-12 and IL-15 by DC may at least partly underlie the difference in susceptibility to L. monocytogenes between C57BL/6 and BALB/c mice.     

New IL-17 family members promote Th1 or Th2 responses in the lung: in vivo function of the novel cytokine IL-25

We have biologically characterized two new members of the IL-17 cytokine family: IL-17F and IL-25. In contrast to conventional in vitro screening approaches, we have characterized the activity of these new molecules by direct in vivo analysis and have compared their function to that of other IL-17 family members. Intranasal administration of adenovirus expressing IL-17, IL-17C, or IL-17F resulted in bronchoalveolar lavage neutrophilia and inflammatory gene expression in the lung. In contrast, intranasal administration of IL-25-expressing adenovirus or IL-25 protein resulted in the production of IL-4, IL-5, IL-13, and eotaxin mRNA in the lung and marked eosinophilia in the bronchoalveolar lavage and lung tissue. Mice given intranasal IL-25 also developed epithelial cell hyperplasia, increased mucus secretion, and airway hyperreactivity. IL-25 gene expression was detected following Aspergillus and Nippostrongylus infection in the lung and gut, respectively. IL-25-induced eosinophilia required IL-5 and IL-13, but not IL-4 or T cells. Following IL-25 administration, the IL-5(+) staining cells were CD45R/B220(+), Thy-1(+/-), but were NK1.1-, Ly-6G(GR-1)-, CD4-, CD3-, and c-kit-negative. gamma-common knockout mice did not develop eosinophilia in response to IL-25, nor were IL-5(+) cells detected. These findings suggest the existence of a previously unrecognized cell population that may initiate Th2-like responses by responding to IL-25 in vivo. Further, these data demonstrate the heterogeneity of function within the IL-17 cytokine family and suggest that IL-25 may be an important mediator of allergic disease via production of IL-4, IL-5, IL-13, and eotaxin.     

Severe impairment in early host defense against Listeria monocytogenes in mice deficient in acid sphingomyelinase

The phagolysosomal compartment is crucial for the defense against infection with intracellular pathogens. Within this compartment, the TNF- and IFN-gamma-responsive acid sphingomyelinase (ASMase) generates the signaling molecule ceramide, resulting in the activation of proteases like cathepsin D. To investigate the possible role of ASMase as a mediator of the antibacterial effects of TNF and IFN-gamma, ASMase(-/-) mice were infected with Listeria monocytogenes. ASMase(-/-) mice showed a dramatically increased susceptibility to L. monocytogenes (LD(50) approximately 100 CFU) when compared with syngeneic wild-type mice (LD(50) approximately 10,000 CFU). In L. monocytogenes-challenged ASMase(-/-) mice, IFN-gamma serum levels as well as IL-1 beta and IL-6 secretion by macrophages were similar to those observed in wild-type C57BL/6 mice. Although macrophages and granulocytes from ASMase(-/-) mice showed intact production of reactive nitrogen intermediates and oxidative burst, ASMase(-/-) macrophages proved completely incapable of restricting the growth of L. monocytogenes in vitro. The results of this study suggest that ASMase is crucially required for the intracellular control of L. monocytogenes in macrophages and granulocytes by nonoxidative mechanisms.