Browsing by Subject "IL-23"
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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.Item THE ROLE OF IL-23 IN REGULATING THE FUNCTION OF PHAGOCYTIC CELLS DURING LISTERIA MONOCYTOGENES INFECTION(2013-04-12) Indramohan, MohanalaxmiPurpose: Listeria monocytogenes (LM) is a Gram-positive intracellular pathogen that causes meningitis and septicemia in immunocompromised individuals, and spontaneous abortion in pregnant women. IL-23 is a pro-inflammatory cytokine that promotes the recruitment of immune cells during multiple infectious and autoimmune diseases. Using IL-23p19 knockout (KO) mice we have demonstrated, that IL-23 is required for resistance against LM, and for the efficient recruitment of neutrophils to the liver, and monocytes to the spleen. However, it is not known whether IL-23 can impact the function of phagocytic cells including monocytes, neutrophils, and macrophages during LM infection. Methods: Mice lacking IL-23p19 (IL-23p19 KO) and C57BL/6 (B6) mice were infected with LM. For the isolation of thioglycollate-elicited peritoneal macrophages, mice were intraperitoneally injected with 1 ml of 2% thioglycollate, three days prior to harvest. Flow cytometry based assays were performed to measure phagocytosis and production of reactive oxygen species (ROS) using the dyes hydroethidine (HE) and 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA). ELISAs were performed to measure the amounts of TNF-ɑ and IL-6. Results: The phagocytic ability of neutrophils and monocytes in the spleen was equivalent between IL-23p19 KO and B6 mice. IL-23p19 KO mice had reduced monocyte-specific ROS production in spleen in comparison to B6 mice. However, the production of monocyte-specific or neutrophil-specific ROS was not induced or enhanced by the addition of recombinant IL-23 to B6 splenocytes. Interestingly, there was a reduction in the production of TNF-ɑ and IL-6 from thioglycollate-elicited peritoneal macrophages from IL-23p19 KO mice compared to B6 mice. Conclusions: IL-23 does not mediate phagocytosis by neutrophils and monocytes. Optimal production of monocyte-derived ROS requires IL-23 during LM infection. However, IL-23 does not directly mediate the production of ROS. Lastly, IL-23 is required for enhancing the production of TNF-ɑ and IL-6 from thioglycollate-elicited peritoneal macrophages.Item The Role of IL-23 in Regulating the Recruitment and Function of Phagocytic Cells during Listeria monocytogenes infection(2014-08-01) Indramohan, Mohanalaxmi; Berg, Rance E.; Mummert, Mark E.; Dory, LadislavThe IL-23/IL-17 axis is detrimental during autoimmune disorders, but is protective against certain pathogens, particularly extracellular bacteria. We have previously shown that IL-23 is required for host resistance against Listeria monocytogenes (LM) and for neutrophil recruitment to the liver, but not the spleen, during infection. Despite efficient neutrophil recruitment to the spleen, IL-23p19 knockout (KO) mice have an increased bacterial burden in this organ compared to C57BL/6 (B6) mice. Interestingly, specific depletion of neutrophils abrogated the differences in bacterial burden in the liver, but not the spleen of B6 and IL-23p19 KO mice, suggesting that IL-23 may regulate the recruitment/function of another cell type in the spleen. Accordingly, LM-infected IL- 23p19 KO mice had fewer inflammatory monocytes in the spleen as well as a reduction in monocyte-recruiting chemokines compared to B6 mice. Therefore, IL-23 is necessary for the optimal recruitment of inflammatory monocytes to the spleen during LM infection. Phagocytic cells express receptors for IL-23 and IL-17A suggesting that the activity of these cells could be regulated by IL-23 or IL-17A. However, it is not known whether IL-23 could impact the function of phagocytic cells during LM infection. Inflammatory monocytes, neutrophils, and macrophages from B6 and IL-23p19 KO mice displayed equivalent phagocytic potential. Although exogenous stimulation with IL-23 and IL-6 increased the production of ROS from B6 neutrophils, the absence of IL-23 did not impact the ability of inflammatory monocytes and neutrophils to make ROS during LM infection. Additionally, the expression of myeloperoxidase (MPO), inducible nitric oxide (iNOS), and TNF-α by inflammatory monocytes, neutrophils, and peritoneal macrophages was not altered by the lack of IL-23 during LM infection. Therefore, IL-23 is not required for the optimal function of phagocytic cells during LM infection. The proinflammatory mediators, TNF-α and NO, are essential for protection against LM. Surprisingly, there was a reduction in the overall levels of TNF-α and NO in the spleen of IL-23p19 KO mice compared to B6 mice during LM infection. However, exogenous stimulation with IL-23 or IL-17A did not induce or enhance the production of these proinflammatory mediators from splenocytes isolated from LM-infected B6 mice. Interestingly, the reduction in overall production of TNF-α and NO. in the spleens of LMinfected IL-23p19 KO mice, corresponds with reduced numbers and percentages of TNF- α and iNOS-expressing monocytes. This deficient recruitment of inflammatory monocytes resulted in decreased production of monocyte-derived TNF-α and NO, leading to increased bacterial burdens in the spleens of LM-infected IL-23p19 KO mice. Collectively, our data reveal that the enhanced susceptibility of IL-23p19 KO mice is not due to functional impairment of phagocytic cells, instead it is caused by the inefficient recruitment of neutrophils to the liver, and inflammatory monocytes to the spleen, during LM infection.