Immunology
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12503/21762
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Browsing Immunology by Author "Berg, Rance E."
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Item EXTRACELLULAR SUPEROXIDE DISMUTASE ENHANCES NEUTROPHIL RECRUITMENT TO THE LIVER BY MODULATING THE EXTRACELLULAR ENVIRONMENT(2014-03) Witter, Alexandra R.; Break, Timothy J.; Indramohan, Mohanalaxmi; Berg, Rance E.Listeria monocytogenes (LM) infection represents one of the leading causes of death from foodborne infection, especially in immunocompromised individuals, and can cause spontaneous abortion in pregnant women; however, it is commonly used as a model to study the host immune response against infection. Our lab utilizes three groups of mice with varying levels of extracellular superoxide dismutase (ecSOD) activity (high, wild-type, and none) to determine the impact that this antioxidant enzyme has on the host immune response during LM infection. We have previously shown that ecSOD activity leads to decreased innate immune response against LM. Our current data shows that ecSOD activity protects the extracellular matrix from degradation, and leads to increased neutrophil recruitment; however, these neutrophils display inhibited function and therefore do not provide adequate protection against LM. This research is relevant due to the potential use of ecSOD inhibitors to enhance immune responses during bacterial infection. In addition, these findings help clarify the impact of the oxidative environment on the immune response and how antioxidants contribute to this dynamic. Purpose (a): 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. Extracellular superoxide dismutase (ecSOD) converts superoxide into hydrogen peroxide in the extracellular milieu and protects against oxidative stress. We have previously shown that ecSOD activity inhibits innate immune responses during LM infection leading to increased bacterial burden; however, it is unclear whether ecSOD activity affects neutrophil recruitment and function in a cell-intrinsic manner or by modulating the extracellular environment. Methods (b): 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 used to perform adoptive transfer experiments after intravenous infection with ~10,000 wild-type LM (WTLM). Either isolated neutrophils or labeled whole bone marrow cells were transferred from ecSOD HI or ecSOD KO mice into ecSOD WT mice and then flow cytometry analysis was performed and colony forming units (CFUs) were calculated. Concentrations of hyaluronan and lymphotoxin alpha were determined by ELISA. Results (c): Whole bone marrow cell transfers indicated that there was no difference in recruitment of neutrophils transferred from ecSOD HI or ecSOD KO mice to the liver when the neutrophils were all in the same environment (ecSOD WT mice). In addition, neutrophils isolated from ecSOD HI or ecSOD KO mice showed no difference in their ability to protect against LM infection, as shown by equivalent CFUs, when in comparable environments (ecSOD WT mice). Analysis of hyaluronan concentrations – a component of the extracellular matrix (ECM) – indicated that ecSOD activity protects the ECM from degradation. Conclusions (d): We observed from adoptive transfer experiments that ecSOD activity does not affect neutrophil recruitment or function in a cell-intrinsic manner. Additionally, we determined that ecSOD activity protects the ECM, which is important for neutrophil trafficking. Overall, we concluded that ecSOD activity enhances neutrophil recruitment yet decreases their function by modulating the extracellular environment.Item FUNCTIONAL REGULATION OF PHAGOCYTIC CELLS BY IL-23 DURING LISTERIA MONOCYTOGENES INFECTION(2014-03) Indramohan, Mohanalaxmi; Break, Timothy J.; Witter, Alexandra R.; Berg, Rance E.Listeria monocytogenes (LM) is a Gram-positive intracellular pathogen that causes meningitis and septicemia in immunocompromised individuals, and spontaneous abortion in pregnant women. The versatility of LM makes it a useful tool for immunologists to understand how the immune system responds against harmful microorganisms. Cell recruitment mediated by the IL-23/IL-17 axis is important for protection against infectious diseases, but can cause damage during autoimmune disorders. By utilizing mice lacking IL-23 (IL-23p19 KO), our lab examines the role of this cytokine during a systemic bacterial infection. We have demonstrated that IL-23 promotes resistance against LM infection by increasing the recruitment of neutrophils to the liver, and monocytes to the spleen during LM infection. Interestingly, IL-23 or IL-17A is not required for enhancing phagocytic cell functions including phagocytosis, production of ROS, MPO, and pro-inflammatory mediators during LM infection. Understanding the significance of IL-23/IL-17axis in mediating the recruitment and function of immune cells will aid in the development of effective therapeutics depending on the disease condition. Purpose (a): Listeria monocytogenes (LM) is a Gram-positive intracellular foodborne pathogen that causes meningitis and septicemia in immunocompromised individuals, and spontaneous abortion in pregnant women. LM is widely used as a model pathogen to study host pathogen immune interactions. Cell recruitment mediated by the IL-23/IL-17 axis is necessary for protection against multiple infectious diseases, but can be detrimental during autoimmune disorders. We have previously shown utilizing mice lacking IL-23 (IL-23p19 KO) that IL-23 provides protection against LM infection by promoting the optimal recruitment of neutrophils to the liver, and monocytes to the spleen. The receptors for IL-23 and IL-17A are present on phagocytic cells including monocytes, neutrophils, and macrophages. However, it is not known whether IL-23 or IL-17A can impact the function of phagocytic cells during LM infection. Methods (b): Splenocytes and liver leukocytes were harvested from mice infected intravenously with ~10, 000 LM. Peritoneal wash was performed to isolate resident peritoneal macrophages. Flow cytometry was utilized to determine phagocytosis, production of reactive oxygen species (ROS), and myeloperoxidase (MPO). The concentrations of TNF-α, IL-1, IL-6, and nitric oxide (NO.) were measured by ELISAs/Griess assay. Results (c): Phagocytic cells isolated from control C57Bl/6 (B6) and IL-23p19 KO mice displayed equivalent phagocytic potential. There were no differences in the production of ROS or MPO from splenocytes isolated from both groups of mice. Furthermore, exogenous stimulation with rIL-23 or rIL-17A did not induce or enhance production of ROS or proinflammatory mediators from B6 splenocytes. Conclusions (d): IL-23 does not impact the function of phagocytic cells either by a direct or indirect mechanism during LM infection. Collectively, our data suggest that the lack of efficient recruitment of neutrophils to the liver, and monocytes to the spleen, results in a reduction in the overall levels of TNF-α and NO. and therefore, increases the susceptibility of IL-23p19 KO to LM infection.