Immunology
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12503/31258
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Browsing Immunology by Subject "ecSOD"
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Item EXTRACELLULAR SUPEROXIDE DISMUTASE ENHANCES NEUTROPHIL RECRUITMENT WHILE DECREASING THEIR FUNCTION(2013-04-12) Break, TimothyPurpose: Listeria monocytogenes (LM) causes spontaneous abortions in pregnant females and septicemia and meningitis in immunocompromised individuals, and results in ~25% mortality rate in infected individuals. Extracellular superoxide dismutase (ecSOD) converts superoxide into hydrogen peroxide in the extracellular milieu and protects against oxidative stress. The use of mice with varying levels of ecSOD serves as a novel approach to determine how an extracellular enzyme can impact immunity against an intracellular pathogen. Methods: Congenic mice with high ecSOD activity (ecSOD HI), wild type ecSOD activity (ecSOD WT), or lacking ecSOD (ecSOD KO), on the C57Bl/6 background, were infected with LM. Colony forming units (CFUs) were counted to determine bacterial load. Percentages of different cell types, cell-surface markers, and intracellular molecules (including ROS and proteins) were determined by flow cytometry. Neutrophil depletions were performed by i.p. injection of anti-Ly6G or isotype control antibody. Cytokine and chemokine concentrations were measured by ELISA. Results: EcSOD HI mice were more susceptible to LM infection than ecSOD WT and ecSOD KO mice. Interestingly, ecSOD HI mice have higher percentages of neutrophils in the liver compared to ecSOD KO mice, which was at least partially mediated by increased ecSOD-induced neutrophil-attracting chemokine production. Neutrophil depletions were performed, and ecSOD WT and KO livers had increased CFUs, while ecSOD HI mice showed slightly decreased CFUs, compared to isotype-treated mice. Furthermore, TNF-ɑ, which is important for clearance of LM, was highest in ecSOD KO mice. Interestingly, ecSOD activity decreased the ability of neutrophils to undergo oxidative burst, a mechanism to kill LM, and increased the amount of LM inside neutrophils. Lastly, ecSOD activity increased the percentage of myeloid-derived suppressor cells, which suppress immune responses. Conclusions: Our data show that ecSOD is detrimental during the early response to LM infection. An increased percentage of neutrophils in ecSOD HI livers, but no concurrent decrease in CFUs, suggests that ecSOD can impair the function of neutrophils. One way this may occur is through the internalization of ecSOD during phagocytosis, which decreases oxidative burst, allowing for LM to survive inside neutrophils. Furthermore, an increase in myeloid-derived suppressor cells in the ecSOD HI livers helps explain why these mice are more susceptible to infection.Item EXTRACELLULAR SUPEROXIDE DISMUTASE MODULATES THE ADAPTIVE IMMUNE RESPONSE DURING SECONDARY INTRACELLULAR BACTERIAL INFECTION(2013-04-12) Witter, AlexandraPurpose: Listeria monocytogenes (LM) is an intracellular foodborne pathogen that causes severe disease in immunocompromised individuals, spontaneous abortion in pregnant women, and results in ~25% mortality rate in infected individuals, making it one of the leading causes of death from foodborne infection. Extracellular superoxide dismutase (ecSOD) converts superoxide into hydrogen peroxide in the extracellular milieu and protects against oxidative stress. While it has been shown that ecSOD decreases innate immune responses during LM infection, its role in a secondary infection model has not been explored. Methods: Congenic mice with high ecSOD activity (ecSOD HI), wild type ecSOD activity (ecSOD WT), or lacking ecSOD (ecSOD KO), on the C57Bl/6 background, were infected with LM/OVA ΔActA and after 40 days challenged with LM/OVA. Colony forming units (CFUs) were counted to determine bacterial burden in the spleen and liver. Percentages of different cell types were determined by flow cytometry. IFN-𝛾 production and concentrations were determined by flow cytometry and ELISA respectively. Results: Our results indicate that ecSOD is protective in a secondary infection since ecSOD HI mice are better able to control bacterial burden than ecSOD KO mice with the ecSOD WT mice showing intermediate CFUs. The ecSOD KO mice exhibit a significantly lower percentage of dendritic cells and corresponding decreases in percentages of both overall CD8 T cells as well as memory CD8 T cells. There was also a decrease in percentages of overall CD4 T cells and memory CD4 T cells, primarily in the spleen. Additionally, there was a significant decrease in CD8 T cell specific IFN-𝛾 production in the spleen after overnight culture with both specific and non-specific stimulation. Conclusions: Our data indicate that ecSOD plays an important role in modulating cell-mediated adaptive immune responses during secondary intracellular bacterial infection. The combination of decreased dendritic cell and CD8 T cell populations, as well as decreased ability of CD8 T cells to produce IFN-𝛾, in ecSOD KO mice suggest that ecSOD may play a role in facilitating the activation of CD8 T cells and their ability to effectively respond during secondary LM infection.