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Introduction: Patient outcome after trauma is influenced by their immune response to injury. How trauma activates the immune system and why this affects recovery is unclear. This investigation examined three aspects of the immune response after trauma: cytokine production, alarmin release and the innate immune cell populations. Methodology: Timed blood samples were drawn from trauma patients recruited to a prospective observational cohort study at a London Major Trauma Centre. The first sample was drawn at admission, within 2h of injury and prior to intervention in order to capture early inflammation events. Patients were observed until death or discharge for clinical outcomes. Results: Inflammation after traumatic tissue damage can be described in isolation. If haemorrhagic shock is also present, the inflammatory effects cannot be separated using the seven cytokines examined in this investigation. Within 2h of injury, isolated tissue damage is associated with systemic release of intracellular nuclear molecules. Tissue damage combined with shock, is associated with release of different nuclear materials. Low numbers of lymphocytes at 48h from injury are associated with poor clinical outcome. Patients who develop infections and multiple organ dysfunction syndrome during recovery, have high numbers of cytotoxic lymphocytes in their peripheral blood at admission. Conclusion: Inflammation is activated prior to arrival at hospital. Haemorrhagic shock augments the inflammatory response after isolated tissue damage. Tissue damage and blood loss may lead to the release of different alarmin substances. Lymphocytes are implicated in the pathogenesis of poor outcome. The molecular events which lead to poor clinical outcome are activated before hospital admission and prior to intervention. Greater understanding of the activation mechanism(s) may result in development of therapeutics for early delivery, in order to improve patient recovery.

Excessive tissue fibrosis in various lung diseases contributes to decline in lung function and subsequent morbidity and mortality. Mechanisms involve complex networks of molecules such as cytokines that are not clearly worked out in conditions such as Idiopathic pulmonary fibrosis (IPF). Furthermore, pulmonary virus infection has been linked to exacerbations of IPF. Previous studies have demonstrated that transient pulmonary over-expression of Oncostatin M (OSM) leads to increased extracellular matrix (ECM) accumulation, Th2-skewed cytokines and Arg1+ M2-like macrophage accumulation in mouse models. OSM can also robustly induce interleukin-33 (IL-33), an IL1 family cytokine or alarmin, both in vivo and in vitro mouse lung systems. Since others have shown that soluble IL-33 exacerbates bleomycin-induced lung fibrosis in mouse models and is associated with Th2-type lung diseases, IL-33 may mediate OSM effects on ECM and Arg1+ macrophage-like cell accumulation. The main hypothesis in this thesis is that OSM can induce IL-33 expression and Arg1+ cells, that OSM can potentiate IL-33 release from virally-infected epithelial cells, and that OSM can prime lungs to subsequent influenza infection and exacerbate pathology. Results demonstrated that OSM induced robust up-regulation of pulmonary IL-33 and Arg1 mRNA and protein expression in vivo, in comparison to another gp130 cytokine, IL-6. However, IL-6 was required for OSM-induced arginase-1 expression in vivo, but not IL-33 expression in vivo. OSM-induced Arg1 expression was also dependent upon IL-33 presence as demonstrated in IL-33-/- animals. This finding implicates a role for both IL-33 and IL-6 in mediating OSM-induced Arg1+ macrophage-like cell accumulation within the lung. Additionally, results showed that a respiratory Influenza A virus infection in vivo alone induced a time-dependent increase in OSM and IL-33 (Day 4), however reduced IL-33 by 7-days post-infection. Influenza infection in AdOSM-primed mice and led to decreased IL-33 expression and eosinophilic infiltration within the lung 5-days post-influenza infection. Collectively, these results demonstrate that OSM can drive Th2-associated pathology correlated to increased IL-33 and Arg1 expression. Contrary to expectations, influenza A virus infection led to a reduction in OSM-induced Th2-phenotype in vivo. Further exploration into the OSM-IL-33 pathway will provide insight into innate immune mechanisms of lung inflammation, virus infection and control of ECM accumulation. / Thesis / Master of Science (MSc)

Le syndrome d'ischémie-reperfusion (IR), inhérent à la transplantation rénale, est caractérisé par un infiltrat leucocytaire important et des lésions tissulaires graves dont les signaux initiateurs restent à ce jour peu décrits. Postulant que la libération d'alarmines par les cellules en nécrose est décisive dans ce processus, l'objectif principal du présent travail a été d'étudier la contribution de l'alarmine IL-33 dans la genèse des lésions tissulaires dans un modèle murin d'IR rénale. Nos résultats montrent que l'IL-33 est rapidement libérée du rein après IR comme protéine circulante, dès une heure de reperfusion. Les souris IL-33gt/gt, déficientes en IL-33, sont moins sensibles aux lésions induites par l’IR, comme l'attestent le maintien de la fonction rénale et des lésions histologiques atténuées avec un recrutement de polynucléaires neutrophiles (PNN) diminué par rapport aux souris contrôles. Ceci est associé à la perte du recrutement de cellules iNKT productrices d'IFN-γ/IL-17A. Parallèlement, les souris Jα18KO, déficientes en cellules iNKT et protégées contre les lésions d'IR, possèdent également des niveaux élevés d'IL-33 circulante. Nous proposons donc que l'IL-33 endogène contribue aux lésions d'IR en favorisant le recrutement de cellules iNKT, conduisant ainsi à un recrutement amplifié de PNN au niveau du rein lésé. Notre étude, en identifiant l'alarmine IL-33 comme un médiateur précoce de la réponse immunitaire innée induite par l'IR rénale, mettant en jeu les cellules iNKT, contribue à la compréhension des mécanismes impliqués dans la genèse des lésions associées à la greffe rénale et permet de proposer de nouvelles stratégies thérapeutiques. / Ischemia-reperfusion (IR) injury in renal transplantation is characterized by leukocyte infiltration and tissue damage. However, the signals that initiate these events remain poorly understood. Assuming that alarmin release by necrotic cells during IRI is critical, the main objective of the present study was to investigate the role of alarmin IL-33 in kidney injury using a mouse model of renal IR. We observed release of IL-33 shortly after kidney IR concomitantly with an increase in plasma levels of IL-33 within one hour of reperfusion. IL-33 deficient mice (IL-33gt/gt) exhibited reduced renal IR-induced injury, as attested by function preservation, reduced histological change and attenuation of neutrophil recruitment compared to control mice. This was associated with the loss of IFN-γ/IL-17A-producing iNKT cell recruitment. In the meantime, iNKT cell-deficient (Jα18KO) mice, also protected against IRI, have increased levels of circulating IL-33.These findings lead us to propose that endogenous IL-33 contributes to kidney IRI by promoting iNKT cell recruitment and cytokine production, thereby promoting amplified neutrophil recruitment to the injured kidney. The present study identifies the nuclear alarmin interleukin (IL)-33 as an important and early mediator of innate immune response, involving iNKT cells, following experimental kidney ischemia-reperfusion in mice. Our findings contribute to a better understanding of IR-induced injury and may lead to new therapeutic insights into renal-induced injury associated with renal transplantation.