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dc.contributor.authorHuggins, Anthony
dc.identifier.citationHuggins,A. 2012. Investigations into the Role of Endogenous Annexin-A1 in Dendritic Cell Biology. Queen Mary University of Londonen_US
dc.description.abstractA school of literature has shown that Annexin-A1 (Anx-A1) is an endogenous anti-inflammatory protein that exerts a regulatory control over the innate immune system in order to restore homeostasis after an inflammatory reaction. Surprisingly, recent published works have highlighted that Anx-A1 has an alternate role in the adaptive immune system by positively modulating the strength of TCR signalling and biasing helper-subset differentiation. Dendritic cells are a class of innate leukocytes, poised at the environmental interface, that are the essential immune cells responsible in the initiation of T-cell driven responses. These findings provided the foundation for this PhD project, the principal aim of which is to provide a link between the disparate effects of Annexin-A1 in innate and adaptive immunity by investigating the role of endogenous Annexin-A1 in dendritic cell biology and its effector function as an antigen-presenting cell towards T cell activation and differentiation. To address this hypothesis, I cultured bone marrowderived dendritic cells from AnxA1-deficient mice or control littermates and stimulated with LPS (100ng/ml) then compared phenotypic and functional characteristics. My results demonstrate that Anx-A1-/- bone marrow derived dendritic cells show an increased number of CD11c+ cells expressing high levels of some maturation markers such as CD40, CD54 and CD80 and a decreased capacity to take up antigen compared to control Anx-A1+/+ cells. However, analysis of LPS-treated dendritic cells from Anx-A1-/- mice demonstrated a diminished up-regulation of maturation markers, a decreased migratory activity in vivo and an attenuated production of the inflammatory cytokines Interleukin (IL)- 1β, Tumour Necrosis Factor (TNF)-α and IL-12. This defect was resultant of an impaired Nuclear Factor (NF)-κB/DNAbinding activity due to lack of Anx-A1 signalling as demonstrated by the reduced activation of Extracellular-signal Regulated Kinase (ERK) 1/2 and protein kinase B (PKB)/Akt compared to cells from control littermates. As a consequence of these defects, I assessed the antigenpresenting/ T-cell activating capabilities of these DC. Anx-A1-/- DC showed an impaired capacity to stimulate T cell proliferation and differentiation in allogeneic mixed leukocyte reaction. To dissect this biologically relevant phenomenon further, I employed an antigenspecific, T-cell restricted model; a co-culture system of chicken ovalbumin peptide-pulsed, LPS-matured bone marrow-derived DC incubated with transgenic TCR T cells from OT-I/RAG-1-/- (OT-I, OTI/ CD8+) or OT-II/ RAG-1-/- (OT-II, OT-II/CD4+) mice. Peptide-pulsed, LPS-matured AnxA1-/- DC failed to initiate an appropriate T cell activation in both OT-I and OT-II T cells indicated by reduced cell proliferation when compared to T cells co-cultured with peptide6 pulsed, LPS-matured AnxA1+/+ DC. Additionally, comparison of peptide-pulsed, LPS-matured AnxA1-/- DC with AnxA1+/+ DC counterparts detected severely diminished levels of IL-2 from cocultures with OT-I T cells and ablated IFN-γ production from cocultures with both OT-I and OT-II T cells. In conclusion, AnxA1 seems to act as a positive modulator of immunogenic activation of DC, whereby the AnxA1 signal pathway has a probable synergism with the TLR4 signalling cascade. DCderived AxnA1 appears to contribute in promoting T cell activation with a larger influence on OT-I/CD8+ T cells than OT-II/CD4+ T cells. Altogether these findings suggest that inhibition of Anx-A1 expression or function in dendritic cells might represent a useful way to modulate the adaptive immune response and pathogen-induced T cell-driven immune diseases.en_US
dc.publisherQueen Mary University of Londonen_US
dc.subjectBiochemical Pharmacologyen_US
dc.titleInvestigations into the Role of Endogenous Annexin-A1 in Dendritic Cell Biologyen_US
dc.rights.holderThe copyright of this thesis rests with the author and no quotation from it or information derived from it may be published without the prior written consent of the author

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    Theses Awarded by Queen Mary University of London

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