CD1d-independent regulation of NKT cell migration and cytokine production upon Listeria monocytogenes infection

Natural killer T (NKT) cells are a unique T-cell population that is positively selected by CD1d-expressing cells. In this study, we examined the kinetics of conventional CD4+TCRbeta+ and CD4-TCRbeta+ cells along with various NKT cell populations from WT and CD1d KO mice after oral Listeria monocytogenes (Lm) infection at different time points in tissue compartments. We found that CD4+TCRbeta+ cells expressing NK1.1+ (NKT) were constitutively expressed in the lung of both strains of mice, but disappeared after infection. In contrast, CD4-TCRbeta+ NK1.1+ cells migrated to the spleen. Here, we demonstrated that endogenous IL-12 was predominantly expressed in the spleen of CD1d KO mice 2 days after infection, whereas IL-4 was predominantly expressed in the liver of WT mice. Higher levels of IFN-gamma were expressed in MLN of CD1d KO but not in WT mice on day 5. Thus, tissue-specific ligands orchestrate the localization and activation of NKT cells to control immune response to Listeria, which may explain the difference in disease susceptibility.     

NKT cells are responsible for the clearance of murine norovirus through the virus-specific secretory IgA pathway

Norovirus infection cause epidemic nonbacterial gastroenteritis in patients. The immune mechanisms responsible for the clearance of virus are not completely understood. We examined whether NKT cells are effective against norovirus infection using CD1d KO mice. The body weights of 4-weeks-old CD1d KO mice that were infected with murine norovirus-S7 (MNV-S7) were significantly lower than those of non-infected CD1d KO mice. On the other hand, the body weights of infected WT mice were comparable to those of non-infected WT mice. Correspondingly, CD1d KO mice had an almost 1000-fold higher MNV-S7 burden in the intestine after infection in comparison to WT mice. The mechanism responsible for the insufficient MNV-S7 clearance in CD1d KO mice was attributed to reduced IFN-γ production early during MNV-S7 infection. In addition, the markedly impaired IL-4 production in CD1d KO mice resulted in an impaired MNV-S7-specific secretory IgA production after MNV-S7 infection which is associated with mucosal immunity. Thus, the present results provide evidence that NKT cells play an essential role in MNV-S7 clearance.     

NKT cells play a limited role in the neutrophilic inflammatory responses and host defense to pulmonary infection with Pseudomonas aeruginosa

CD1d-restricted NKT cells are reported to play a critical role in the host defense to pulmonary infection with Pseudomonas aeruginosa. However, the contribution of a major subset expressing a Valpha14-Jalpha18 gene segment remains unclear. In the present study, we re-evaluated the role of NKT cells in the neutrophilic inflammatory responses and host defense to this infection using mice genetically lacking Jalpha18 or CD1d (Jalpha18KO or CD1dKO mice). These mice cleared the bacteria in lungs at a comparable level to wild-type (WT) mice. There was no significant difference in the local neutrophilic responses, as shown by neutrophil counts and synthesis of MIP-2 and TNF-alpha, in either KO mice from those in WT mice. Administration of alpha-galactosylceramide, a specific activator of Valpha14+ NKT cells, failed to promote the bacterial clearance and neutrophilic responses, although the same treatment increased the synthesis of IFN-gamma, suggesting the involvement of this cytokine downstream of NKT cells. In agreement against this notion, these responses were not further enhanced by administration of recombinant IFN-gamma in the infected Jalpha18KO mice. Our data indicate that NKT cells play a limited role in the development of neutrophilic inflammatory responses and host defense to pulmonary infection with P. aeruginosa.     

CD1d1-dependent control of the magnitude of an acute antiviral immune response

CD1d1-restricted NK T (NKT) cells rapidly secrete both Th1 and Th2 cytokines upon activation and are therefore thought to play a regulatory role during an immune response. In this study we examined the role of CD1d1 molecules and NKT cells in regulating virus-induced cytokine production. CD1d1-deficient (CD1KO) mice, which lack NKT cells, were infected with lymphocytic choriomeningitis virus, and spontaneous cytokine release from splenocytes was measured. We found that CD1KO mice produce significantly higher amounts of IL-2, IL-4, and IFN-gamma compared with wild-type controls postinfection. Depletion studies of individual lymphocyte subpopulations suggested that CD4+ T cells are required; however, isolation of specific lymphocyte populations indicated that CD4+ T cells alone are not sufficient for the increase in cytokine production in CD1KO mice. Splenocytes from lymphocytic choriomeningitis virus-infected CD1KO mice continued to produce enhanced cytokine levels long after viral clearance and cleared viral RNA faster than wild-type mice. There was no difference in the number of splenocytes between uninfected wild-type and CD1KO mice, whereas the latter knockout mice had an increased number of splenocytes after infection. Collectively, these data provide clear evidence that the expression of CD1d1 molecules controls the magnitude of the cell-mediated immune response to an acute viral infection.     

CD1d mediates T-cell-dependent resistance to secondary infection with encephalomyocarditis virus (EMCV) in vitro and immune response to EMCV infection in vivo

The innate and adaptive immune responses have evolved distinct strategies for controlling different viral pathogens. Encephalomyocarditis virus (EMCV) is a picornavirus that can cause paralysis, diabetes, and myocarditis within days of infection. The optimal innate immune response against EMCV in vivo requires CD1d. Interaction of antigen-presenting cell CD1d with distinct natural killer T-cell ("NKT") populations can induce rapid gamma interferon (IFN-gamma) production and NK-cell activation. The T-cell response of CD1d-deficient mice (lacking all NKT cells) against acute EMCV infection was further studied in vitro and in vivo. EMCV persisted at higher levels in CD1d-knockout (KO) splenocyte cultures infected in vitro. Furthermore, optimal resistance to repeat cycles of EMCV infection in vitro was also shown to depend on CD1d. However, this was not reflected in the relative levels of NK-cell activation but rather by the responses of both CD4(+) and CD8(+) T-cell populations. Repeated EMCV infection in vitro induced less IFN-gamma and alpha interferon (IFN-alpha) from CD1d-deficient splenocytes than with the wild type. Furthermore, the level of EMCV replication in wild-type splenocytes was markedly and specifically increased by addition of blocking anti-CD1d antibody. Depletion experiments demonstrated that dendritic cells contributed less than the combination of NK and NKT cells to anti-EMCV responses and that none of these cell types was the main source of IFN-alpha. Finally, EMCV infection in vivo produced higher levels of viremia in CD1d-KO mice than in wild-type animals, coupled with significantly less lymphocyte activation and IFN-alpha production. These results point to the existence of a previously unrecognized mechanism of rapid CD1d-dependent stimulation of the antiviral adaptive cellular immune response.     

Invariant V alpha 14+ NKT cells participate in the early response to enteric Listeria monocytogenes infection

Invariant Valpha14(+) NKT cells are a specialized CD1-reactive T cell subset implicated in innate and adaptive immunity. We assessed whether Valpha14(+) NKT cells participated in the immune response against enteric Listeria monocytogenes infection in vivo. Using CD1d tetramers loaded with the synthetic lipid alpha-galactosylceramide (CD1d/alphaGC), we found that splenic and hepatic Valpha14(+) NKT cells in C57BL/6 mice were early producers of IFN-gamma (but not IL-4) after L. monocytogenes infection. Adoptive transfer of Valpha14(+) NKT cells derived from TCRalpha degrees Valpha14-Jalpha18 transgenic (TCRalpha degrees Valpha14Tg) mice into alymphoid Rag(null) gamma(c)(null) mice demonstrated that Valpha14(+) NKT cells were capable of providing early protection against enteric L. monocytogenes infection with systemic production of IFN-gamma and reduction of the bacterial burden in the liver and spleen. Rechallenge experiments demonstrated that previously immunized wild-type and Jalpha18null mice, but not TCRalpha(null) or TCRalpha(null) Valpha14Tg mice, were able to mount adaptive responses to L. monocytogenes. These data demonstrate that Valpha14(+) NKT cells are able to participate in the early response against enteric L. monocytogenes through amplification of IFN-gamma production, but are not essential for, nor capable of, mediating memory responses required to sterilize the host.     

Critical role of NK cells rather than V alpha 14(+)NKT cells in lipopolysaccharide-induced lethal shock in mice

Although macrophages play a central role in the pathogenesis of septic shock, NK1(+) cells have also been implicated. NK1(+) cells comprise two major populations, namely NK cells and V alpha 14(+)NKT cells. To assess the relative contributions of these NK1(+) cells to LPS-induced shock, we compared the susceptibility to LPS-induced shock of beta(2)-microglobulin (beta(2)m)(-/-) mice that are devoid of V alpha 14(+)NKT cells, but not NK cells, with that of wild-type (WT) mice. The results show that beta(2)m(-/-) mice were more susceptible to LPS-induced shock than WT mice. Serum levels of IFN-gamma following LPS challenge were significantly higher in beta(2)m(-/-) mice, and endogenous IFN-gamma neutralization or in vivo depletion of NK1(+) cells rescued beta(2)m(-/-) mice from lethal effects of LPS. Intracellular cytokine staining revealed that NK cells were major IFN-gamma producers. The J alpha 281(-/-) mice that are exclusively devoid of V alpha 14(+)NKT cells were slightly more susceptible to LPS-induced shock than heterozygous littermates. Hence, LPS-induced shock can be induced in the absence of V alpha 14(+)NKT cells and IFN-gamma from NK cells is involved in this mechanism. In WT mice, hierarchic contribution of different cell populations appears likely.     

Role of interferon-gamma in Valpha14+ natural killer T cell-mediated host defense against Streptococcus pneumoniae infection in murine lungs

Previously, we demonstrated that Valpha14+ NKT cells and IFN-gamma are important upstream components in neutrophil-mediated host defense against infection with Streptococcus pneumoniae. In the present study, we extended these findings by elucidating the role of IFN-gamma in this Valpha14+ NKT cell-promoted process. Administration of recombinant IFN-gamma to Jalpha18KO mice prolonged the shortened survival, promoted the attenuated clearance of bacteria and improved the reduced accumulation of neutrophils and synthesis of MIP-2 and TNF-alpha in the lungs, in comparison to wild-type (WT) mice. In addition, intravenous transfer of liver mononuclear cells (LMNC) from WT mice into Jalpha18KO mice resulted in complete recovery of the depleted responses listed above, whereas such effects were not detected when LMNC were obtained from IFN-gammaKO or Jalpha18KO mice. Activation of Valpha14+ NKT cells by alpha-galactosylceramide (alpha-GalCer) significantly enhanced the clearance of bacteria, accumulation of neutrophils and synthesis of MIP-2 and TNF-alpha in the infected lungs; this effect was significantly inhibited by a neutralizing anti-IFN-gamma antibody. Finally, in a flow cytometric analysis, TNF-alpha synthesis was detected largely by CD11b(bright+) cells in the infected lungs. Our results demonstrated that IFN-gamma plays an important role in the neutrophil-mediated host protective responses against pneumococcal infection promoted by Valpha14+ NKT cells.     

Regulation by Src homology 2 domain-containing protein tyrosine phosphatase substrate-1 of alpha-galactosylceramide-induced antimetastatic activity and Th1 and Th2 responses of NKT cells

Interaction of alpha-galactosylceramide (alpha-GalCer) presented by CD1d on dendritic cells (DCs) with the invariant TCR of NKT cells activates NKT cells. We have now investigated the role of Src homology 2 domain-containing protein tyrosine phosphatase substrate-1 (SHPS-1), a transmembrane protein abundantly expressed on DCs, in regulation of NKT cells with the use of mice that express a mutant form of SHPS-1. The suppression by alpha-GalCer of experimental lung metastasis was markedly attenuated in SHPS-1 mutant mice compared with that apparent in wild-type (WT) mice. The antimetastatic effect induced by adoptive transfer of alpha-GalCer-pulsed DCs from SHPS-1 mutant mice was also reduced compared with that apparent with WT DCs. Both the production of IFN-gamma and IL-4 as well as cell proliferation in response to alpha-GalCer in vitro were greatly attenuated in splenocytes or hepatic mononuclear cells from SHPS-1 mutant mice compared with the responses of WT cells. Moreover, CD4+ mononuclear cells incubated with alpha-GalCer and CD11c+ DCs from SHPS-1 mutant mice produced markedly smaller amounts of IFN-gamma and IL-4 than did those incubated with alpha-GalCer and CD11c+ DCs from WT mice. SHPS-1 on DCs thus appears to be essential for alpha-GalCer-induced antimetastatic activity and Th1 and Th2 responses of NKT cells. Moreover, our recent findings suggest that SHPS-1 on DCs is also essential for the priming of CD4+ T cells by DCs.     

The antiviral efficacy of the murine alpha-1 interferon transgene against ocular herpes simplex virus type 1 requires the presence of CD4(+), alpha/beta T-cell receptor-positive T lymphocytes with the capacity to produce gamma interferon

Alpha/beta interferons (IFN-alpha/betas) are known to antagonize herpes simplex virus type 1 (HSV-1) infection by directly blocking viral replication and promoting additional innate and adaptive, antiviral immune responses. To further define the relationship between the adaptive immune response and IFN-alpha/beta, the protective effect induced following the topical application of plasmid DNA containing the murine IFN-alpha 1 transgene onto the corneas of wild-type and T-cell-deficient mice was evaluated. Mice homozygous for both the T-cell receptor (TCR) beta- and delta-targeted mutations expressing no alpha beta or gamma delta TCR (alpha beta/gamma delta TCR double knockout [dKO]) treated with the IFN-alpha 1 transgene succumbed to ocular HSV-1 infection at a rate similar to that of alpha beta/gamma delta TCR dKO mice treated with the plasmid vector DNA. Conversely, mice with targeted disruption of the TCR delta chain and expressing no gamma delta TCR(+) cells treated with the IFN-alpha 1 transgene survived the infection to a greater extent than the plasmid vector-treated counterpart and at a level similar to that of wild-type controls treated with the IFN-alpha 1 transgene. By comparison, mice with targeted disruption of the TCR beta chain and expressing no alpha beta TCR(+) cells (alpha beta TCR knockout [KO]) showed no difference upon treatment with the IFN-alpha1 transgene or the plasmid vector control, with 0% survival following HSV-1 infection. Adoptively transferring CD4(+) but not CD8(+) T cells from wild-type but not IFN-gamma-deficient mice reestablished the antiviral efficacy of the IFN-alpha 1 transgene in alpha beta TCR KO mice. Collectively, the results indicate that the protective effect mediated by topical application of a plasmid construct containing the murine IFN-alpha 1 transgene requires the presence of CD4(+) T cells capable of IFN-gamma synthesis.     

NK cells play a critical protective role in host defense against acute extracellular Staphylococcus aureus bacterial infection in the lung

Staphylococcus aureus remains a common cause of nosocomial bacterial infections and are often antibiotic resistant. The role of NK cells and IL-15 and their relationship in host defense against extracellular bacterial pathogens including S. aureus remain unclear. We have undertaken several approaches to address this issue using wild type (WT), IL-15 gene knock-out (KO), and NK cell-depleted mouse models. Upon pulmonary staphylococcal infection WT mice had markedly increased activated NK cells, but not NKT or gammadelta T cells, in the airway lumen that correlated with IL-15 production in the airway and with alveolar macrophages. In vitro exposure to staphylococcal products and/or coculture with lung macrophages directly activated NK cells. In contrast, lung macrophages better phagocytosed S. aureus in the presence of NK cells. In sharp contrast to WT controls, IL-15 KO mice deficient in NK cells were found to be highly susceptible to pulmonary staphylococcal infection despite markedly increased neutrophils and macrophages in the lung. In further support of these findings, WT mice depleted of NK cells were similarly susceptible to staphylococcal infection while they remained fully capable of IL-15 production in the lung at levels similar to those of NK-competent WT hosts. Our study thus identifies a critical role for NK cells in host defense against pulmonary extracellular bacterial infection and suggests that IL-15 is involved in this process via its indispensable effect on NK cells, but not other innate cells. These findings hold implication for the development of therapeutics in treating antibiotic-resistant S. aureus infection.     

In vivo assessment of natural killer cell responses during chronic feline immunodeficiency virus infection

Accumulating evidence suggests that natural killer (NK) cells may have an important role in HIV-1 disease pathogenesis; however, in vivo studies are lacking. Feline immunodeficiency virus (FIV) infection of cats provides a valuable model to study NK cell function in vivo. The immune response against Listeria monocytogenes (Lm) is well characterized, allowing its use as an innate immune probe. We have previously shown that locally delivered IL-15 can improve Lm clearance in FIV-infected animals, and this correlated with an increase in NK cell number. In the present study, chronically FIV-infected and SPF-control cats were challenged with Lm by unilateral subcutaneous injection next to the footpad and then treated with 5-bromo-2'-deoxyuridine (BrdU). The Lm draining and contralateral control lymph nodes were evaluated for NK, NKT, CD4+ and CD8+ T cell number, proliferation, apoptosis, and NK cell function. Listeria monocytogenes burden was also assessed in both control and Lm draining lymph nodes. NK, NKT, CD4+ T and CD8+ T cells in the Lm-challenged lymph node of FIV-infected cats did not increase in number. In addition, after Lm challenge, NK cells from FIV-infected cats did not increase their proliferation rate, apoptosis was elevated, and perforin expression was not upregulated when compared to SPF-control cats. The failure of the NK cell response against Lm challenge in the draining lymph node of FIV-infected cats correlates with the delayed control and clearance of this opportunistic bacterial pathogen.     

NK T cell activation promotes Chlamydia trachomatis infection in vivo

We used two approaches to examine the role of NK T cells (NKT) in an intracellular bacterial (Chlamydia trachomatis mouse pneumonitis (C. muridarum)) infection. One is to use CD1 gene knockout (KO) mice, which lack NKT, and the other is to activate NKT using alpha-galactosylceramide (alpha-GalCer), a natural ligand of these cells. The data showed a promoting effect of NKT activation on Chlamydia lung infection. Specifically, CD1 KO mice exhibited significantly lower levels of body weight loss, less severe pathological change and lower chlamydial in vivo growth than wild-type mice. Immunological analysis showed that CD1 KO mice exhibited significantly lower C. muridarum-specific IL-4 and serum IgE Ab responses as well as more pronounced delayed-type hypersensitivity response compared with wild-type controls. In line with the finding in KO mice, the in vivo stimulation of NKT using alpha-GalCer enhanced chlamydial growth in vivo, which were correlated with reduced delayed-type hypersensitivity response and increased C. muridarum-driven IL-4/IgE production. Moreover, neutralization of IL-4 activity in the alpha-GalCer-treated BALB/c mice significantly reduced the promoting effect of alpha-GalCer treatment on chlamydial growth in vivo. These data provide in vivo evidence for the involvement of NKT in a bacterial pathogenesis and its role in promoting Th2 responses during infection.     

IL-4-secreting NKT cells prevent hypersensitivity pneumonitis by suppressing IFN-gamma-producing neutrophils

Hypersensitivity pneumonitis (HP) is mediated by Th1 immune response. NKT cells regulate immune responses by modulating the Th1/Th2 balance. Therefore, we postulated that NKT cells play a critical role in the development of the HP by modulating the Th1/Th2 response. To address this issue, we explored the functional roles of NKT cells in Saccharopolyspora rectivirgula (SR)-induced HP. In CD1d(-/-) mice, the HP was worse in terms of histological changes, hydroxyproline levels, the CD4:CD8 ratio in bronchoalveolar lavage fluid, and SR-specific immune responses than in control mice. CD1d(-/-) mice showed elevated IFN-gamma production in the lung during the HP, and this was produced mainly by Gr-1+ neutrophils. The blockade of IFN-gamma in CD1d(-/-) mice attenuated the HP, whereas the injection of rIFN-gamma aggravated it. Moreover, the depletion of Gr-1+ neutrophils reduced CD8+ T cell numbers in bronchoalveolar lavage fluid during the HP. The adoptive transfer of IL-4(-/-) mouse NKT cells did not attenuate the HP, whereas wild-type or IFN-gamma(-/-) mouse NKT cells suppressed the HP. In conclusion, NKT cells producing IL-4 play a protective role in SR-induced HP by suppressing IFN-gamma-producing neutrophils, which induce the activation and proliferation of CD8+ T cells in the lung.     

Ecto-5'-nucleotidase (CD73) decreases mortality and organ injury in sepsis

The extracellular concentrations of adenosine are increased during sepsis, and adenosine receptors regulate the host's response to sepsis. In this study, we investigated the role of the adenosine-generating ectoenzyme, ecto-5'-nucleotidase (CD73), in regulating immune and organ function during sepsis. Polymicrobial sepsis was induced by subjecting CD73 knockout (KO) and wild type (WT) mice to cecal ligation and puncture. CD73 KO mice showed increased mortality in comparison with WT mice, which was associated with increased bacterial counts and elevated inflammatory cytokine and chemokine concentrations in the blood and peritoneum. CD73 deficiency promoted lung injury, as indicated by increased myeloperoxidase activity and neutrophil infiltration, and elevated pulmonary cytokine levels. CD73 KO mice had increased apoptosis in the thymus, as evidenced by increased cleavage of caspase-3 and poly(ADP-ribose) polymerase and increased activation of NF-κB. Septic CD73 KO mice had higher blood urea nitrogen levels and increased cytokine levels in the kidney, indicating increased renal dysfunction. The increased kidney injury of CD73 KO mice was associated with augmented activation of p38 MAPK and decreased phosphorylation of Akt. Pharmacological inactivation of CD73 in WT mice using α, β-methylene ADP augmented cytokine levels in the blood and peritoneal lavage fluid. These findings suggest that CD73-derived adenosine may be beneficial in sepsis.     

IL-10 modulates host responses and lung damage induced by Pneumocystis carinii infection

Host responses to Pneumocystis carinii infection mediate impairment of pulmonary function and contribute to the pathogenesis of pneumonia. IL-10 is known to inhibit inflammation and reduce the severity of pathology caused by a number of infectious organisms. In the present studies, IL-10-deficient (IL-10 knockout (KO)) mice were infected with P. carinii to determine whether the severity of pathogenesis and the efficiency of clearance of the organisms could be altered in the absence of IL-10. The clearance kinetics of P. carinii from IL-10 KO mice was significantly enhanced compared with that of wild-type (WT) mice. This corresponded to a more intense CD4(+) and CD8(+) T cell response as well as an earlier neutrophil response in the lungs of IL-10 KO mice. Furthermore, IL-12, IL-18, and IFN-gamma were found in the bronchoalveolar lavage fluids at earlier time points in IL-10 KO mice suggesting that alveolar macrophages were activated earlier than in WT mice. However, when CD4(+) cells were depleted from P. carinii-infected IL-10 KO mice, the ability to enhance clearance was lost. Furthermore, CD4-depleted IL-10 KO mice had significantly more lung injury than CD4-depleted WT mice even though the intensity of the inflammatory responses was similar. This was characterized by increased vascular leakage, decreased oxygenation, and decreased arterial pH. These data indicate that IL-10 down-regulates the immune response to P. carinii in WT mice; however, in the absence of CD4(+) T cells, IL-10 plays a critical role in controlling lung damage independent of modulating the inflammatory response.     

Chlamydia trachomatis mouse pneumonitis lung infection in IL-18 and IL-12 knockout mice: IL-12 is dominant over IL-18 for protective immunity

BACKGROUND: Interferon (IFN)-gamma is a key to protective immunity against a variety of intracellular bacterial infections, including Chlamydia trachomatis. Interleukin (IL)-18, a recently identified Th1 cytokine, together with IL-12 is a strong stimulator for IFN-gamma production. We investigated the relative roles of IL-18 and IL- 12 in protective immunity to C. trachomatis mouse pneumonitis (MoPn) infection using gene knockout (KO) and wild-type (WT) mice. MATERIALS AND METHODS: Mice were intranasally infected with C. trachomatis MoPn and protective immunity was assessed among groups of mice by daily body weight changes, lung growth of MoPn, and histopathological appearances at day 10 postinfection. The corresponding immune responses for each group of mice at the same postinfection time point were evaluated by measuring antigen-specific antibody isotype responses and cytokine profiles. RESULTS: Our results showed that IL-18 deficiency had little or no influence on clearance of MoPn from the lung, although KO mice exhibited slightly more severe inflammatory reactions in lung tissues, as well as reduced systemic and local IFN-gamma production, compared with WT mice. Results with IL-18 KO mice were in sharp contrast to those observed with IL-12 KO mice that showed substantially reduced clearance of MoPn from the lungs, substantial reductions of antigen-specific systemic and lung IFN-gamma production, decreased ratio of MoPn-specific immunoglobulin G (IgG)2a/IgG1, and severe pathological changes in the lung with extensive polymorphonuclear, instead of mononuclear, cell infiltration. Exogenous IL-12 or IL-18 was able to increase IFN-gamma production in IL-18 KO mice; whereas, only exogenous IL-12, but not IL-18, enhanced IFN-gamma production in IL-12 KO mice. Caspase-1 is the key protease for activation of IL-18 precursor into the bioactive form, and caspase-1 KO mice also displayed similar bacterial clearance and body weight loss to that in WT mice at early stages of MoPn infection. This further confirmed that IL-18 was not essential for host defense against chlamydia infection. CONCLUSIONS: These results suggest that IL-12, rather than IL-18, plays the dominant role in the development of protective immunity against chlamydia lung infection, although both cytokines are involved in the in vivo regulation of IFN-gamma production.     

CD1d-restricted IFN-γ-secreting NKT cells promote immune complex-induced acute lung injury by regulating macrophage-inflammatory protein-1α production and activation of macrophages and dendritic cells

Immune complex-induced acute lung injury (IC-ALI) has been implicated in various pulmonary disease states. However, the role of NKT cells in IC-ALI remains unknown. Therefore, we explored NKT cell functions in IC-ALI using chicken egg albumin and anti-chicken egg albumin IgG. The bronchoalveolar lavage fluid of CD1d(-/-) and Jα18(-/-) mice contained few Ly6G(+)CD11b(+) granulocytes, whereas levels in B6 mice were greater and were increased further by α-galactosyl ceramide. IFN-γ and MIP-1α production in the lungs was greater in B6 than CD1d(-/-) mice. Adoptive transfer of wild type (WT) but not IFN-γ-, MIP-1α-, or FcγR-deficient NKT cells into CD1d(-/-) mice caused recruitment of inflammatory cells to the lungs. Moreover, adoptive transfer of IFN-γR-deficient NKT cells enhanced MIP-1α production and cell recruitment in the lungs of CD1d(-/-) or CD1d(-/-)IFN-γ(-/-) mice, but to a lesser extent than WT NKT cells. This suggests that IFN-γ-producing NKT cells enhance MIP-1α production in both an autocrine and a paracrine manner. IFN-γ-deficient NKT cells induced less IL-1β and TNF-α production by alveolar macrophages and dendritic cells in CD1d(-/-) mice than did WT NKT cells. Taken together, these data suggest that CD1d-restricted IFN-γ-producing NKT cells promote IC-ALI by producing MIP-1α and enhancing proinflammatory cytokine production by alveolar macrophages and dendritic cells.     

Impaired clearance of herpes simplex virus type 1 from mice lacking CD1d or NKT cells expressing the semivariant V alpha 14-J alpha 281 TCR

Ag-presenting molecule CD1 and CD1-restricted NKT cells are known to contribute to defense against a range of infectious pathogens, including some viruses. CD1-restricted NKT cells, a distinct subpopulation of T cells, have striking and rapid effector functions that contribute to host defense, including rapid production of IFN-gamma and IL-4, and activation of NK cells. Consideration of the important contributions of innate and adaptive immunity to clearance of HSV prompted us to investigate the role of CD1 and of NKT cells expressing the V alpha 14-J alpha 281 TCR in the pathogenesis of HSV infection. To address this issue, we compared infection in wild-type mice with that in CD1 gene knockout (GKO) and J alpha 281 GKO mice. In this study, we report impaired clearance of virus and viral Ags, and more florid acute infection in mice lacking CD1 (and by inference, CD1-restricted T cells), in comparison with parental C57BL6 mice. In J alpha 281 GKO mice there was also impairment of virus clearance, resembling that seen in CD1 GKO mice. These results imply roles for the V alpha 14-J alpha 281 subset of NKT cells and for CD1d in control of HSV infection.