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The mechanism of gamma interferon (IFN-{gamma}) production induced by listeriolysin O (LLO), a cytolytic virulence factor of Listeria monocytogenes, was analyzed with special reference to the involvement of macrophage-derived cytokines in spleen cells of mice. LLO purified from the culture supernatant of L. monocytogenes was capable of inducing a high level of IFN-{gamma} when its cytolytic activity was blocked by cholesterol treatment. The IFN-{gamma}-inducing ability of LLO was not dependent on possibly contaminating lipopolysaccharide. Depletion of CD11b+ cells resulted in a profound decrease in IFN-{gamma} production in response to LLO stimulation. Negative selection also suggested the contribution of DX5+ cells in IFN-{gamma} production. Reverse transcription-PCR revealed that expression of interleukin-12 (IL-12) p35 and p40 was i...

The mechanism of gamma interferon (IFN-) production induced by listeriolysin O (LLO), a cytolytic virulence factor of Listeria monocytogenes, was analyzed with special reference to the involvement of macrophage- derived cytokines in spleen cells of mice. LLO purified from the culture supernatant of L. monocytogenes was capable of inducing a high level of IFN- when its cytolytic activity was blocked by cholesterol treatment. The IFN--inducing ability of LLO was not dependent on possibly contaminating lipopolysaccharide. Depletion of CD11b cells resulted in a profound decrease in IFN- production in response to LLO stimulation. Negative selection also suggested the contribution of DX5 cells in IFN- production. Reverse transcription- PCR revealed that expression of interleukin-12 (IL-12) p35 and p40 was induced by LLO but that the IL-18 mR...

The mechanism of gamma interferon (IFN-γ) production induced by listeriolysin O (LLO), a cytolytic virulence factor of Listeria monocytogenes, was analyzed with special reference to the involvement of macrophage-derived cytokines in spleen cells of mice. LLO purified from the culture supernatant of L. monocytogenes was capable of inducing a high level of IFN-γ when its cytolytic activity was blocked by cholesterol treatment. The IFN-γ-inducing ability of LLO was not dependent on possibly contaminating lipopolysaccharide. Depletion of CD11b+ cells resulted in a profound decrease in IFN-γ production in response to LLO stimulation. Negative selection also suggested the contribution of DX5+ cells in IFN-γ production. Reverse transcription-PCR revealed that expression of interleukin-12 (IL-12) p35 and p40 was induced by LLO but that the IL-...

Two pathogenic species in the genus Listeria, Listeria monocytogenes and Listeria ivanovii, are characterized by the production of hemolysins belonging to cholesterol-dependent cytolysins, listeriolysin O (LLO) and ivanolysin O (ILO), respectively. LLO, produced by L. monocytogenes, is able to induce gamma interferon (IFN-γ) production and contributes to the generation of Th1-dependent protective immunity. On the other hand, nothing is known about the role of ILO, produced by L. ivanovii, in this regard. In this study, we immunized mice with 0.1 50% lethal dose (LD50) of L. monocytogenes and L. ivanovii. Protective immunity against a challenge with 10 LD50 was generated in mice infected with L. monocytogenes, whereas L. ivanovii infection did not induce protection. After immunization, the level of IFN-γ in serum samples was increased i...

The inflammasome adaptor ASC contributes to innate immunity through the activation of caspase-1. Here we found that signaling pathways dependent on the kinases Syk and Jnk were required for the activation of caspase-1 via the ASC-dependent inflammasomes NLRP3 and AIM2. Inhibition of Syk or Jnk abolished the formation of ASC specks without affecting the interaction of ASC with NLRP3. ASC was phosphorylated during inflammasome activation in a Syk- and Jnk-dependent manner, which suggested that Syk and Jnk are upstream of ASC phosphorylation. Moreover, phosphorylation of Tyr144 in mouse ASC was critical for speck formation and caspase-1 activation. Our results suggest that phosphorylation of ASC controls inflammasome activity through the formation of ASC specks.