• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 180
  • 88
  • 62
  • 36
  • 24
  • 11
  • 6
  • 4
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 510
  • 510
  • 109
  • 108
  • 87
  • 61
  • 60
  • 57
  • 56
  • 54
  • 54
  • 51
  • 51
  • 48
  • 47
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

New Insights into the Regulation of Intestinal Immunity by Nod1 and Nod2

Rubino, Stephen 02 April 2014 (has links)
Nod1 and Nod2 are intracellular pattern recognition receptors that detect specific moieties of peptidoglycan, a critical component of the bacterial cell wall, to initiate host innate immune responses. Importantly, mutations in the human NOD2 gene have been associated with increased risk to develop mucosal auto-inflammatory disorders such as Crohn’s Disease. However, how Nod1 and Nod2 mediate mucosal homeostasis still remains unclear. In Chapter 2, I determined that mice deficient for both Nod1 and Nod2 (Nod1-/-Nod2-/-) exhibited delayed induction of intestinal inflammation at early timepoints after infection with Citrobacter rodentium compared to wild-type mice, which correlated with compromised control of the pathogen at later timepoints. Notably, I determined that induction of the cytokines IL-17 and IL-22 in the cecal lamina propria (LP) was blunted in Nod1-/-Nod2-/- mice after infection with either C. rodentium or Salmonella enterica serovar Typhimurium. Importantly, I found that Th17 cells were the principal producers of IL-17 and IL-22 after infection. Due to the rapid kinetics of activation and the regulation by Nod1 and Nod2, I termed this early mucosal response the innate Th17 (iTh17) response. The iTh17 cells exhibited an effector memory phenotype and required priming from the enteric microbiota for full induction. Therefore, in Chapter 3, I next determined that major histocompatibility complex (MHC) class II expression in hematopoietic cells was required for the induction of LP Th17 responses after infection. Interestingly, I found that the percentage IL-17+CD8+ T cells was strongly upregulated when MHCII signaling was ablated, suggesting a dynamic compensatory mechanism of IL-17-producing T cell responses in the mucosa. In Chapter 4, I identified MDP(D-Glu2)-OCH3 as a synthetic Nod2 agonist that exhibited increased stimulatory ability of Nod2-dependent NF-B activation compared to MDP in an unbiased screen. Moreover, I determined that MDP(D-Glu2)-OCH3 induced more potent inflammatory responses both in vitro and in vivo and was a better adjuvant than MDP. Together, the data presented in this thesis expand our current understanding of the roles of Nod1 and Nod2 in the intestinal LP, the regulation of IL-17 producing T cells in the gut and the therapeutic potential of novel Nod2 agonists.
2

New Insights into the Regulation of Intestinal Immunity by Nod1 and Nod2

Rubino, Stephen 02 April 2014 (has links)
Nod1 and Nod2 are intracellular pattern recognition receptors that detect specific moieties of peptidoglycan, a critical component of the bacterial cell wall, to initiate host innate immune responses. Importantly, mutations in the human NOD2 gene have been associated with increased risk to develop mucosal auto-inflammatory disorders such as Crohn’s Disease. However, how Nod1 and Nod2 mediate mucosal homeostasis still remains unclear. In Chapter 2, I determined that mice deficient for both Nod1 and Nod2 (Nod1-/-Nod2-/-) exhibited delayed induction of intestinal inflammation at early timepoints after infection with Citrobacter rodentium compared to wild-type mice, which correlated with compromised control of the pathogen at later timepoints. Notably, I determined that induction of the cytokines IL-17 and IL-22 in the cecal lamina propria (LP) was blunted in Nod1-/-Nod2-/- mice after infection with either C. rodentium or Salmonella enterica serovar Typhimurium. Importantly, I found that Th17 cells were the principal producers of IL-17 and IL-22 after infection. Due to the rapid kinetics of activation and the regulation by Nod1 and Nod2, I termed this early mucosal response the innate Th17 (iTh17) response. The iTh17 cells exhibited an effector memory phenotype and required priming from the enteric microbiota for full induction. Therefore, in Chapter 3, I next determined that major histocompatibility complex (MHC) class II expression in hematopoietic cells was required for the induction of LP Th17 responses after infection. Interestingly, I found that the percentage IL-17+CD8+ T cells was strongly upregulated when MHCII signaling was ablated, suggesting a dynamic compensatory mechanism of IL-17-producing T cell responses in the mucosa. In Chapter 4, I identified MDP(D-Glu2)-OCH3 as a synthetic Nod2 agonist that exhibited increased stimulatory ability of Nod2-dependent NF-B activation compared to MDP in an unbiased screen. Moreover, I determined that MDP(D-Glu2)-OCH3 induced more potent inflammatory responses both in vitro and in vivo and was a better adjuvant than MDP. Together, the data presented in this thesis expand our current understanding of the roles of Nod1 and Nod2 in the intestinal LP, the regulation of IL-17 producing T cells in the gut and the therapeutic potential of novel Nod2 agonists.
3

Mutational analysis of the dsRNA binding domain of Vaccinia Virus E3 protein

Dick, Kevin James 08 September 2011 (has links)
Vaccinia virus E3 protein is known to bind double-stranded RNA and mediate interferon resistance. Alanine scanning mutagenesis was performed on its dsRNA binding domain, sufficient for wild-type tropism and immune suppression in vitro, and dsRNA binding and host range function assayed. Residues involved in dsRNA binding were required for host range function; however, seven dsRNA binding mutants were unable to rescue ΔE3L replication. Utilizing recombinant viruses, non-rescue mutants were unable to inhibit protein Kinase R phosphorylation despite dsRNA binding. Furthermore, host range was found to correlate with cytokine suppression and replication in IFN stimulated Huh7R cells. Additionally, no direct association was found between dsRNA binding and PKR interaction, refining the suppression model. Novel protein-protein interactions were discovered between E3 and cellular proteins via differential gel electrophoresis. This study represents the first full mapping of E3 residues involved in dsRNA binding and tropism, forming a basis for future study.
4

Mutational analysis of the dsRNA binding domain of Vaccinia Virus E3 protein

Dick, Kevin James 08 September 2011 (has links)
Vaccinia virus E3 protein is known to bind double-stranded RNA and mediate interferon resistance. Alanine scanning mutagenesis was performed on its dsRNA binding domain, sufficient for wild-type tropism and immune suppression in vitro, and dsRNA binding and host range function assayed. Residues involved in dsRNA binding were required for host range function; however, seven dsRNA binding mutants were unable to rescue ΔE3L replication. Utilizing recombinant viruses, non-rescue mutants were unable to inhibit protein Kinase R phosphorylation despite dsRNA binding. Furthermore, host range was found to correlate with cytokine suppression and replication in IFN stimulated Huh7R cells. Additionally, no direct association was found between dsRNA binding and PKR interaction, refining the suppression model. Novel protein-protein interactions were discovered between E3 and cellular proteins via differential gel electrophoresis. This study represents the first full mapping of E3 residues involved in dsRNA binding and tropism, forming a basis for future study.
5

Ethanol-induced toxicity and neurodegeneration in C. elegans

Gomez, Lina Maria 02 December 2013 (has links)
Alcohol abuse is an enormous problem causing death and disability to over 43 million people worldwide each year (WHO). Chronic alcohol consumption also contributes to abnormal brain morphology and significant brain volume loss indicative of neurodegeneration. Until there are effective treatments to alter maladaptive behavioral patterns in alcohol abuse, more research is needed to prevent alcohol-induced toxicity and degeneration. We used C. elegans as a model system to identify genetic modulators of alcohol toxicity and explored whether prolonged alcohol exposure damages the nervous system. In our study, we exposed L4-larval stage worms to varying concentrations of ethanol for three days and found a dose-dependent deficit in crawling. Furthermore, we evaluated degeneration by assessing the health of neurons using fluorescent reporters. Compared to the untreated group, we found that ethanol-exposed worms had a significant neurodegeneration. Previous findings using C. elegans have suggested that the innate immune pathway may protect against neurodegeneration caused by drug toxicity (Schreiber & McIntire, 2012). We find that deletion of either the innate immune gene nsy-1 (orthologous to the mammalian ASK-1 MAPKKK) or pmk-1 (orthologous to the mammalian p38 MAPK) caused hypersensitivity to ethanol toxicity. Conversely, boosting innate immune signaling via gain-of-function mutation in nsy-1 produced resistance to ethanol toxicity and ameliorated ethanol-induced cholinergic degeneration. Our findings indicate that prolonged exposure to ethanol leads to both behavioral impairments and neuronal degeneration in C. elegans and that the ASK1/p38 MAP kinase pathway may play a role in ethanol-induced damage to the nervous system. / text
6

Interaction between Macrophages and Epithelial Cells in Innate Immune Responses against Adenoviral Vectors

Lee, Benjamin 17 December 2012 (has links)
Although induction of innate immune responses during viral infection is essential, it can cause acute inflammation and lead to devastating results. The deleterious effect of innate immune responses has been demonstrated in gene therapy where administration of a replication deficient adenoviral vector (Ad) caused fatality during a clinical trial. Despite recent advances in our understanding of the innate immunity, there is a lack of understanding on how different cell types interact to mount inflammatory responses, which may play an important role in regulating immune responses in vivo. In this study, we investigated the interaction between macrophages and epithelial cells, the two major cell types capable of sensing and responding to viral infection in the airway, in induction of inflammatory responses against replication deficient Ads. We show in Chapter 2 that Ad infection of the macrophage-epithelial cell co-culture resulted in synergistic induction of inflammatory responses. Ad infection of the co-culture compared to macrophages alone resulted in higher cytotoxicity and induction of significantly higher levels of inflammatory mediators including pro-inflammatory cytokines, chemokines, nitric oxide, and reactive oxygen species. We found that these synergistic responses require macrophages and epithelial cells to be in close proximity suggesting that a novel mechanism regulates the inflammatory responses. In Chapter 3, we studied whether ATP plays a role in regulating inflammatory responses during acute Ad infection. Using the co-culture system, we found that ATP signaling through P2X7 receptor (P2X7R) is critical as inhibition or deficiency of P2X7R resulted in reduced inflammatory responses. We demonstrate that ATP-P2X7R signaling regulates inflammasome activation and IL-1β secretion. Furthermore, intranasal administration of Ad resulted in high mortality in mice but inhibition of ATP-P2X7R signaling enhanced survival and reduced inflammatory responses. These results suggest that ATP released by the infected cells plays an important role in regulating inflammatory responses during acute viral infection.
7

Interaction between Macrophages and Epithelial Cells in Innate Immune Responses against Adenoviral Vectors

Lee, Benjamin 17 December 2012 (has links)
Although induction of innate immune responses during viral infection is essential, it can cause acute inflammation and lead to devastating results. The deleterious effect of innate immune responses has been demonstrated in gene therapy where administration of a replication deficient adenoviral vector (Ad) caused fatality during a clinical trial. Despite recent advances in our understanding of the innate immunity, there is a lack of understanding on how different cell types interact to mount inflammatory responses, which may play an important role in regulating immune responses in vivo. In this study, we investigated the interaction between macrophages and epithelial cells, the two major cell types capable of sensing and responding to viral infection in the airway, in induction of inflammatory responses against replication deficient Ads. We show in Chapter 2 that Ad infection of the macrophage-epithelial cell co-culture resulted in synergistic induction of inflammatory responses. Ad infection of the co-culture compared to macrophages alone resulted in higher cytotoxicity and induction of significantly higher levels of inflammatory mediators including pro-inflammatory cytokines, chemokines, nitric oxide, and reactive oxygen species. We found that these synergistic responses require macrophages and epithelial cells to be in close proximity suggesting that a novel mechanism regulates the inflammatory responses. In Chapter 3, we studied whether ATP plays a role in regulating inflammatory responses during acute Ad infection. Using the co-culture system, we found that ATP signaling through P2X7 receptor (P2X7R) is critical as inhibition or deficiency of P2X7R resulted in reduced inflammatory responses. We demonstrate that ATP-P2X7R signaling regulates inflammasome activation and IL-1β secretion. Furthermore, intranasal administration of Ad resulted in high mortality in mice but inhibition of ATP-P2X7R signaling enhanced survival and reduced inflammatory responses. These results suggest that ATP released by the infected cells plays an important role in regulating inflammatory responses during acute viral infection.
8

Neonatal innate immunity

Macpherson, Stephanie 03 September 2009 (has links)
The neonatal period represents a critical time period in the development of the immune system. Adaptive human immune responses are generally viewed as immature at birth. However little is known about innate immune capacity at birth. The TLR system plays an integral role as pattern recognition receptors in the innate immune response. It is also critical in initiating and regulating the adaptive immune response. Preterm birth is associated with increased risk of developing infections in early life and has been associated with increased risk of development of other chronic disorders in later life; however the underlying mechanisms are not at all well understood. Recently, late preterm neonates (34-36 weeks gestation vs full term, 37+ weeks) have been identified as having significantly greater risks of morbidity and mortality in the perinatal period than their full term counterparts. Hence, we focus on examination of TLR responses in late preterm and full term neonates to better understand immune potential and function in these populations. We examined cord blood cytokine and chemokine responses following stimulation with a broad range of TLR agonists. Our results show for the first time that late preterm neonates have reduced capacity to produce both pro- and anti-inflammatory cytokines following stimulation with a panel of TLR agonists. This reduced responsiveness was not due to a reduction in the number of responding cells, but instead appears to be mediated by a reduction in the intrinsic levels of expression of TLRs and associated adaptor proteins. Because little is known about how the innate immune system develops throughout life, we next compared TLR responses in full term neonates to 7 children, adolescents and adults. We found that neonates had selective impairments in TLR responses, most notably in anti-inflammatory cytokine production and anti-viral immune responses compared to the other age groups. Epigenetic modifications, such as the addition or removal of acetyl groups to histone proteins by histone acetyl transferase (HAT) and histone deactylase (HDAC) respectively, are able to modify the expression of genes. Hence, environmental stimuli have been shown to influence gene expression in part by modifying the level or activity of these epigenetic regulators. Currently there are no studies which have examined how epigenetic modifications may influence neonatal innate immune responses. Hence, we sought to determine how modulation of endogenous HDAC activity would affect neonatal innate immune responses. We found that inhibition of HDAC had both inhibitory and enhancing effects on cytokine expression depending on the TLR pathway activated, indicating that the endogenous HDAC expression does not have a global inhibitory impact on all TLR-dependent responses. In summary, this body of work demonstrates that neonatal innate immune responses vary depending on gestational age, indicating that the final few weeks of gestation are crucial for maturation of responses to both bacteria and viruses. Neonates respond differently to TLR stimuli than do older individuals, further highlighting a maturation process of the innate immune system which continues throughout life. Finally, we have shown that environmental exposures may have powerful effects on immune responses in early life.
9

Regulation of TGFβ-activated-kinase 1 (TAK1) in nuclear factor-κB and tumour necrosis factor/Eiger signalling in Drosophila melanogaster

Fernando, Merennege Dilan Anush January 2011 (has links)
Drosophila TGFbeta-Activating-Kinase 1 (dTAK1) is an essential component of both the Immune Deficiency (IMD) innate immune and TNF/Eiger apoptotic cascades. The IMD and JNK pathways bifurcate at the level of dTAK1. Hence, elucidating the regulatory mechanism of dTAK1 is pertinent to understanding the regulation of both innate immunity and apoptosis. In this study, Trabid was identified as a novel negative regulator of the Drosophila IMD pathway. Trabid interacted with dTAK1 and decreased K63-linked ubiquitination, thereby reducing immune signalling. Three tandem Npl4 Zinc Fingers (NZF) and C518 were required for Trabid activity. Lysines 142 & 156 were identified as the K63 Ub acceptor sites of dTAK1, required for K63-linked ubiquitination and signalling. Also, results show Lys 156 functioned as the K48 Ub acceptor site. Further, the ZF domain of TAK1-associated Binding Protein 2 (dTAB2) was important in modulating dTAK1 K63-linked ubiquitination and thereby the immune signal. These results indicate an elaborate and multi-tiered mechanism for regulating dTAK1 activity and modulating the immune signal. Further, Ariadne-2 (Ari-2) was identified as a novel component of the Drosophila TNF/Eiger pathway which functioned at the level of dTAK1. Results indicate that Ari-2 is essential for normal development and longevity. It enhances the apoptotic signal when concomitantly over-expressed with Eiger. Further, Ari-2 interacts with dTAK1, dTAB2 and dTRAF2 which are all implicated in TNF/Eiger signalling. Thus, evidence supports the hypothesis that Ari-2 functions as an adaptor, involved in assembling a distinct signalling complex which transduces the apoptotic signal without activating immunity.
10

Novel functions of Tribbles 1 in macrophages

Liu, Yi-Hsia January 2012 (has links)
Tribbles (Trib) protein was first described in Drosophila as a regulator of proliferation, later being implicated as a G2/M modulator. In mammalian systems, three Trib gene family members have been identified, which share a conserved motif similar to the catalytic domain of serine/threonine kinases. However, they lack several conserved residues in the ATP-binding pocket and the core motif of the catalytic domain necessary for catalytic function. Tribbles 1 (Trib1) is involved in inflammation through its ability to regulate MAPK, NF-κB and the CCAAT Enhancer Binding Protein (C/EBP). Moreover, Trib1 is associated with human disease, such as atherosclerosis and acute myeloid leukaemia. In this thesis, I investigated the functional role of Trib1 in Toll-like Receptor (TLR)-induced inflammatory responses together with pro- or anti-inflammatory cytokines. The RAW264.7 myeloid cell line was stimulated with TLR2/9 ligands in the presence or absence of IFN-γ or IL-10. I observed a high level of Trib1 expression in the presence of IFN-γ and TLR2 ligands, but weak Trib1 expression following treatment with IL-10 and TLR9 ligands. In gene knock-down experiments using small interfering RNAs (siRNA) to reduce Trib1 expression, C/EBPβ was up-regulated in both stimulated (by IFN-γ and TLR2 ligands) and resting macrophage populations. TNF-α production was increased following Trib1 knockdown after treatment with IFN-γ and/or TLR2 ligands but IL-6 secretion remained unchanged. Furthermore, ERK1/2 expression was reduced in Trib1 siRNA-treated cells and failed to induce chemokinesis in macrophages. Finally, Trib1 was demonstrated to act as a modulator of cell cycle (G2/M) transition and displays a delayed apoptotic phenotype. The work in this thesis demonstrates that mammalian Trib1 contributes to the pro-inflammatory response and functions as a regulator of the ERK1/2 and C/EBPβ pathways following TLR ligand-mediated activation. Its novel functions include acting as a modulator of G2/M arrest and suppressing macrophage migration.

Page generated in 0.0716 seconds