Le vieillissement de la population est à l’origine de l’augmentation du nombre de personnes souffrant de démences, dont la plus fréquente est la maladie d’Alzheimer (MA). La MA est une maladie neurodégénérative incurable caractérisée par une atteinte progressive des fonctions cognitives, en premier lieu les fonctions mnésiques. Son diagnostic formel repose sur l’examen post-mortem du cerveau des patients. Il est basé sur la présence conjointe de deux lésions caractéristiques: des dépôts extracellulaires majoritairement composés de peptide amyloïde fibrillaire, résultat d’un clivage anormal du précurseur transmembranaire APP, et d’une dégénérescence neurofibrillaire ou pathologie tau, caractérisée par l’accumulation intra-neuronale de protéines tau hyper- et anormalement phosphorylées. Parallèlement à ces deux lésions se développe une réponse neuro-inflammatoire, notamment caractérisée par une augmentation du nombre et de l’activité des cellules microgliales et astrocytaires. Bien que les relations entre la pathologie amyloïde et la mise en place des processus neuro-inflammatoires aient fait l’objet d’intenses investigations, peu d’études se sont intéressés aux liens réciproques existants entre ces processus et la pathologie tau. A travers l’utilisation d’un modèle murin transgénique mimant le versant tau de la MA, la lignée THY-Tau22, un des objectifs de ma thèse a consisté à caractériser les différents aspects de leur réponse neuro-inflammatoire. Ces souris développent une pathologie tau hippocampique progressive associée à des altérations mnésiques. Les études transcriptomiques, biochimiques et histologiques réalisées ont mis en évidence une augmentation progressive de l’expression hippocampique de marqueurs de l’immunité innée mais également adaptative chez les souris THY-Tau22. Nous observons particulièrement l’établissement progressif de réactions microgliales et astrocytaires, une augmentation des niveaux de différentes chimiokines (CCL3, CCL4 et CCL5) conjointement à une infiltration parenchymateuse de lymphocytes T, en l’absence d’altération majeure de l’intégrité de la barrière hémato-encéphalique. Ces résultats mettent en exergue une corrélation entre le développement de troubles mnésiques et de la pathologie Tau hippocampique d’une part, et la présence d’une réponse neuro-inflammatoire d’autre part. La MA est une maladie multifactorielle dont la survenue est modulée par différents facteurs génétiques et environnementaux. Parmi les facteurs environnementaux mis en évidence par les études épidémiologiques, la consommation de caféine réduit notablement le risque de développer la MA. La caféine est une substance psychoactive dont les effets sont essentiellement médiés par le blocage des récepteurs adénosinergiques A1 et A2A, ces derniers étant particulièrement décrits pour moduler les processus neuroinflammatoires. Le rôle de ces récepteurs étant mal connus dans le contexte de la MA, et inconnu concernant ses relations à la pathologie Tau, la seconde partie de ma thèse a consisté à évaluer les effets de la caféine mais également d’un blocage spécifique des récepteurs A2A, par des approches génétiques et pharmacologiques, vis-à-vis des altérations comportementales, de la pathologie tau et de la réponse neuro-inflammatoire dans le modèle THY-Tau22. Les résultats obtenus démontrent que la caféine et le blocage spécifique des récepteurs A2A exercent des effets bénéfiques dans ce modèle de Tauopathie, avec une prévention des altérations mnésiques, une réduction de l’hyperphosphorylation de Tau et des effets anti-inflammatoires. Ces modifications sont associées à des effets bénéfiques en terme neurochimique et synaptique. L’ensemble de ces résultats démontrent pour la première fois un effet bénéfique de la caféine et du blocage des récepteurs A2A dans un modèle murin de tauopathie et suggèrent qu’un ciblage thérapeutique de ces récepteurs puisse être d’intérêt dans la MA. / Population ageing is a major risk factor for dementia, the most prevalent being Alzheimer disease (AD). AD is a neurodegenerative disorder characterized by a progressive cognitive decline, notably impacting memory functions. Its formal diagnosis is based on the post-mortem examination of AD patients’ brains and defined by the combination of two lesions: extracellular deposition of fibrillar amyloid peptide, resulting from the abnormal cleavage of transmembrane APP precursor, and neurofibrillary tangles, characterized by intraneuronal accumulation of hyper- and abnormal phosphorylated tau protein (Tau pathology). Besides these two lesions hallmarks, neuro-inflammatory processes, mainly defined by an increase of the number and the activity of microglial and astroglial cells, are considered as a third pathological component. Although the relationships between amyloid pathology and neuro-inflammatory processes had been the subject of intense investigations, few studies has been achieved with regards to tau pathology. As a first aim of this work, neuro-inflammatory processes associated with Tau pathology has been evaluated using a transgenic mouse model mimicking AD-like Tau pathology, THY-Tau22 strain.. These mice overexpress a mutated human tau protein under the control of a neuronal promoter and progressively hippocampal tau pathology associated to memory decline. Transcriptomic, biochemical and histological evaluations revealed a progressive increase several markers of both innate and adaptive immunity in the hippocampus of THY-Tau22 transgenic mice. We notably observed a progressive rise of microglial and astrogliale reactions, the overproduction of many chemokines (CCL3, CCL4, CCL5) in association with a parenchymatous infiltration of T cells, without major disruption of blood brain barrier (BBB). These results highlight a correlation between the establishments of memory alterations and hippocampal tau pathology on the one hand, and the occurrence of a neuro-inflammatory response on the other hand. AD is a multifactorial disorder whose occurrence depends on different genetic and environmental factors. Among the latter, epidemiological studies have shown that caffeine consumption significantly reduces the risk to develop AD. Caffeine is a psychoactive drug, whose effects are mainly ascribed to the blockade of A1 and A2A adenosinergic receptors, the latter beeing known to modulate neuro-inflammatory processes. The role of A2A receptors in AD is far from understood, and relationship with tau pathology currently unknown. The second part of my PhD aimed at evaluating effects of caffeine but also of a specific A2AR blockade, using genetic and pharmacological means, towards behavioural alterations, tau pathology and neuro-inflammatory processes in THY-Tau22 model. Results obtained demonstrate that caffeine and specific A2AR blockade lead to beneficial effects towards memory dysfunction, tau hyperphosphorylation and hippocampal neuro-inflammation. These improvements are associated with beneficial neurochemical and electrophysiological changes. Theses results demonstrate for the first time a beneficial effect of caffeine and A2A receptor blockade in a mouse model of tauopathy and support that therapeutic targeting of A2A receptors could be of interest in AD.

A polpa dental é formada de tecido conjuntivo frouxo sendo constituída por diversas células, dentre as quais os fibroblastos são as mais numerosas. Ao serem submetidas a agressões diversas, estas células respondem com a liberação de substâncias, tais como citocinas e quimiocinas, que participam de maneira ativa no processo inflamatório. Assim sendo, este trabalho teve como proposição: 1. avaliar a capacidade de fibroblastos de polpa dental humana em cultura em produzirem as quimiocinas MIP-l\'alfa\' /CCL3 e SDF-1/CXCL12; 2. avaliar a produção destas quimiocinas pelos fibroblastos quando estimulados por Enterococcus faecalis morto por calor com relação à quantidade de bactérias por célula e 3. avaliar a liberação destas quimiocinas com relação ao tempo de estímulo. Para o estabelecimento das culturas, foi coletada a polpa de terceiro molar hígido de um paciente saudável. O tecido foi extraído, armazenado e picotado em meio de cultura para fibroblastos (DMEM), os quais foram utilizados a partir da quarta passagem. Após adesão das células a placas de 24 poços, o meio de cultura contendo Enterococcus .faecalis morto por calor numa concentração correspondente a 1, 10 e 100 bactérias por fibroblasto foi adicionado aos poços. Após 1, 6 e 24 horas, o sobrenadante das células foi coletado para a análise por ELISA. A análise estatística foi realizada aplicando-se o teste Kruskal-Wallis com nível de significância de 5%. A produção de MIP-l\'alfa\' /CCL3 e SDF-l/CXCL12 pelas células pôde ser detectada por ELISA. Os fibroblastos pulpares se mostraram capazes de produzir SDF-1 constitutivamente sendo que o estímulo bacteriano levou a uma diminuição estatisticamente significativa desta produção. A produção de MIP-l\'alfa\' também foi detectada tanto de maneira constitutiva como em resposta ao desafio microbiano. Enquanto a concentração intermediária de bactéria por fibroblasto (10:1) mostrou uma produção semelhante ao grupo controle, as concentrações de 1 e 100 bactérias por fibroblasto induziram aumento maior na primeira hora de estímulo. Essas diferenças, entretanto, não foram estatisticamente significativas. A capacidade dos fibroblastos secretarem quimiocinas, como MIP-l\'alfa\' e SDF-1, reforça a importância dessas células dentro do contexto de imunidade e inflamação pulpar, principalmente por serem as células mais numerosas deste microambiente. / Dental pulp is a connective tissue structure constituted by many different cell types. Among them, the fibroblasts are the most frequent ones. When challenged by different aggressive agents, these cells are able to release some substances like cytokines and chemokines, which are essential to trigger the inflammatory process. The aims of this study were: 1. to evaluate the ability of fibroblasts to produce the chemokines MIP-l\'alfa\'/CCL3) and SDF-1/CXCL12; 2. to evaluate the expression of these chemokines by fibroblasts when challenged by heat killed Enterococcus. faecalis in gradual concentrations and 3. to evaluate the production of these chemokines in a time course manner. The dental pulp from non-carious third molar was collected from a healthy patient. Explants were made and stocked in culture medium (DMEM) for fibroblasts growth. The cells were used since passage four. In a 24-well plate and after reaching confluence, culture medium alone or containing heat killed E. faecalis at proportion 1:1, 10:1 and 100:1 bacteria:fibroblast, were added to the fibroblasts. After 1, 6 and 24 hours, the supernatants were collected for analysis. The protein detection of MIP-l\'alfa\'/CCL3 and SDF-1/CXCL12 was performed by ELISA. For statistical analysis, data were assessed by Kruskal-Wallis followed by Miller post-test. Significance levels of 5% were adopted. Production of both chemokines was detected by ELISA. Pulp fibroblasts were able to produce SDF-1 constitutively. This production decreased with the increase in the number of heat killed E. faecalis increased (p < 0.05). Production of MIP-l\'alfa\' was detected in unchallenged and challenged cells. The median bacterial concentration (10:1) presented a profile production similar to that of unstimulated cells. Bacterial concentrations of 1 and 100 microrganisms/cell showed a highly enhanced production of MIP-l\'alfa\' at the first hour of stimulum; however, these data were not statistically significant (p > 0.05). Fibroblasts ability to produce chemokines, like MIP-l\'alfa\' and SDF-1, confirms their importance at immune and inflammatory events in dental pulp, specially being fibroblasts the most abundant cells at this microenvironment .

University of Macau / Institute of Chinese Medical Sciences

A meta-clorofenilpiperazina (1-(3-clorofenil)piperazina; mCPP) é uma piperazina sintética que vem sendo apreendida de forma crescente no mercado de drogas ilícitas, primeiro na Europa e, a partir de 2006, também no Brasil. Recentemente há relatos de aumento significativo da apreensão de comprimidos vendidos como ecstasy e que na realidade contêm mCPP, porém estudos sobre potenciais riscos dessa utilização à saúde ainda são escassos. O papel da mCPP como agonista de receptores serotoninérgicos já está bem descrito na literatura, razão pela qual esta substância é amplamente empregada em trabalhos científicos, principalmente psiquiátricos. No entanto, poucos são os trabalhos realizados com o intuito de investigar mais profundamente as ações desencadeadas no organismo pela substância em si. É sabido que a serotonina é um neurotransmissor liberado por plaquetas no local de inflamação e que exerce papel imunomodulatório importante sobre as células imune Assim, considerando (1) a relevância atual da mCPP no contexto de apreensão de drogas de abuso, (2) a necessidade de estudos sobre efeitos das drogas de abuso no organismo, (3) escassez de avaliações dos efeitos da mCPP sobre o sistema imunológico e (4) sua provável correlação com este sistema a partir de suas ações em receptores serotoninérgicos, o presente trabalho pretendeu iniciar investigações acerca da atividade da mCPP sobre as respostas imune inatas e sobre os mecanismos da mobilização leucocitária. Para tanto, ratos Wistar machos foram tratados com mCPP (1mg/kg, v.o.) e foram realizadas quantificações de leucócitos na medula óssea, no compartimento circulante e no foco inflamatório (peritônio), em presença ou ausência de estímulo inflamatório (LPS, 1 mg/mL, i.p.), como também da mieloperoxidase presente em tecido hepático, pulmonar e do baço. Complementando os estudos in vivo, ainda foi quantificada a cortisona plasmática em animais que receberam tal tratamento tendo seus receptores de glicocorticoides previamente antagonizados (RU38486). Neutrófilos coletados do exsudato peritoneal foram incubados nas concentrações de 10 &#181;M, 100 &#181;M e 1000 &#181;M in vitro e investigados a migração neutrofílica, a expressão das moléculas de adesão na superfície neutrofílica, a quantificação de mediadores inflamatórios no sobrenadante de cultura de neutrófilos e o processo de adesão neutrófilo-endotélio, com células endoteliais coletados a partir do cremáster. Os resultados demonstram que a mCPP diminuiu a quantificação de leucócitos no exsudato peritoneal e, concomitantemente, aumentou o influxo de PMN para o tecido pulmonar, em vigência de estímulo inflamatório. Ainda, in vivo, não foi possível observar diferenças na concentração de cortisona sérica entre animais cujos receptores de glicocorticóides foram antagonizados e aqueles cujos receptores em questão encontravam-se normais. In vitro, a mCPP, nas três concentrações empregadas, e tanto na vigência quanto na ausência de estímulo (LPS ou fMLP), causou alterações na migração dos neutrófilos, na adesão deste tipo celular ao endotélio, na expressão de moléculas de adesão (Lselectina, &#946;2-integrina e PECAM-1) na superfície neutrofílica e na quantificação das concentrações de mediadores inflamatórios (NO, IL-1&#946;, IL-10, TNF-&#945;) no sobrenadante de cultura de neutrófilos. Os resultados obtidos sugerem, em conjunto, que a mCPP exerce atividade pró-inflamatória no que se refere à atividade neutrofílica, bem como sugerem que o fármaco seja capaz de amplificar a resposta inflamatória em modelo animal de rato, tanto in vivo quanto in vitro. / The meta-chlorophenylpiperazine is a synthetic piperazine which has been seized increasingly in the illicit drug market, primarily in Europe and after 2006, in Brazil. Recently, there has been a significant increase on the apprehension of tablets sold as ecstasy but that in reality contain mCPP. Despite its importance, studies over its potential health risks are few. The mCPP role as serotonergic receptor agonist is well known in the literature, reason why this substance is widely employed in scientific research, particularly in psychiatric studies. But there are few reports that aim to investigate thoroughly the actions that this substance triggers in the organisms. It is also known that serotonin is a neurotransmitter released by platelets at the site of inflammation and plays important immunomodulatory role on immune cells. Therefore, considering (1) the relevance of mCPP in the drug abuse context nowadays, (2) the necessity of researching the effects of the drug abuse in the organisms, (3) the lack of studies containing analysis of the mCPP effects over the immune system and (4) the probable correlation between mCPP and this system, through its activity in serotoninergic receptors, this report intended to lead investigations about the mCPP activity over the innate immune response and over the leukocyte mobilization mechanisms. For this purpose, Wistar male rats were treated with mCPP (1mg/kg, v.o.), their leukocytes were measured in the bone marrow, in the circulating compartment and in the inflammatory foci (peritoneum) in the presence or absence of inflammatory stimuli (LPS, 1 mg/mL, i.p.) and the myeloperoxidase present in liver tissue, lung and spleen was also quantified. In addition to in vivo studies, the cortisone plasma was quantified in animals receiving such treatment with glucocorticoid receptors antagonized previously (RU38486). Neutrophils collected from the peritoneal exudate were incubated at concentrations of 10 mM, 100 mM and 1000 mM in vitro. It was then investigated the neutrophil migration and the expression of adhesion molecules on the surface of neutrophils as well as the quantification of inflammatory mediators in the culture supernatant. The process of neutrophil-neutrophil adhesion to endothelium was also analyzed and endothelial cells were collected from the cremaster. Results reflect that mCPP decreased the amount of leukocytes at the peritoneal exudate and, concomitantly, increased the influx of PMN into the lung tissue during an inflammatory stimulus. Also, in vivo, it was possible to observe differences in the concentration of serum from animals which cortisone glucocorticoid receptors were previously antagonized and those in which the receptors in question were normal. In vitro, mCPP in three concentrations employed, and both in the presence or absence of stimulus (LPS or fMLP) caused changes in the migration of neutrophils, in the cell adhesion to the endothelium, in the expression of adhesion molecules (L-selectin, integrin-&#946;2 and PECAM-1), on the surface of neutrophils and in the concentrations of inflammatory mediators (NO, IL-1&#946;, IL-10, TNF-&#945;) in the culture supernatant of neutrophils. The results suggest that, together, mCPP exerts pro-inflammatory activity with respect to neutrophil activity. They also suggest that the drug is able to amplify the inflammatory response in an animal model rat both in vivo and in vitro.

O objetivo do presente estudo foi avaliar aspectos histológicos, imuno-histoquímicos e ultraestruturais da resposta inflamatória induzida experimentalmente, através da inoculação de BCG por via intramuscular em peixes filogeneticamente primitivos do gênero Arius sp e modernos do gênero Centropomus sp, com o intuito de estabelecer parâmetros comparativos da resposta inflamatória do ponto de vista filogenético entre peixes modernos e primitivos. Os resultados mostram haver diferenças na resposta inflamatória entre peixes modernos e primitivos; sendo que o primeiro tem capacidade de organização da lesão em granulomas típicos e células epitelióides secretoras de proteína S100 e citoqueratina, e que ao longo do experimento desenvolveu junções desmossômicas entre si; enquanto peixes primitivos não possuem capacidade de organização da lesão, não formando granulomas, apenas células gigantes secretoras de proteína S100. Não houve participação expressiva de células gigantes e pigmentares na resposta inflamatória no gênero Centropomus sp, sugerindo ser uma característica relacionada à espécie, contrariando alguns resultados verificados em peixes modernos no que diz respeito à participação de células pigmentares. / The aim of this study was the evaluation of the histological, imunohistochemical and ultra structural aspect of the inflammatory response experimentally induced by BCG intramuscular injection in phylogenetically primitive fishes of the genera Arius sp and modern of the genera Centropomus sp, with the purpose of establishing comparative parameters of the inflammatory response between modern and primitive fishes about phylogenetic aspect. The results show differences in the inflammatory response between modern and primitive fishes. Modern fishes have the ability of organization of the lesion, with development of tipical granulomas and epithelioid cells that produce S100 protein, cytokeratin and throughout the experiment they developed desmosomic junctions; instead of primitive fishes that don?t show the ability of organization of the lesion without forming an granuloma, just giant cells that produce S100 protein. It didn?t have an expressive participation of giant cells and pigmentcontaining cells in the inflammatory reaction in genera Centropomus sp, suggesting that It is a specie-specific characteristic, in opposition to some results found in modern fishes about pigment cells participation in the inflammatory reaction of modern fishes.

Pancreatic adenocarcinoma (PDAC) is the fourth leading cause of cancer death in Western countries. The PDAC tumour microenvironment (TME) is characterized by a dense stromal reaction, consisting of many cell types including fibroblasts and immune cells. The chemokine receptor, CX3CR1 forms a high-affinity axis with its unique ligand CX3CL1 and is expressed on monocytes, macrophages and T cells. CX3CR1 is also present on pancreatic malignant cells, where it has been associated with metastasis formation. The aim of my project is to investigate the role of CX3CR1 in the progression and development of pancreatic cancer in a genetically engineered mouse model of PDAC, the CX3CR1GFP/GFPLSL-KRASG12D/+LSL-Trp53R172H/+Pdx1-Cre (CKPC) mouse. In these mice, the CX3CR1 protein is not functional but they express GFP. I have found that the absence of CX3CR1 in KPC mice has no effect in their lifespan and response to chemotherapy. Comparison of the immune infiltrate of the tumours revealed that the lack of CX3CR1 causes a significant decrease in T cells and a possible increase in myeloid cells in CKPC mice compared to KPC mice. Expression analysis of several inflammatory cytokines in the TME showed a significant difference in IL-10 between KPC and CKPC mice. There was also a significant increase in levels of, CX3CL1, both locally and in the plasma. Finally, we performed RNA-seq on KPC and CKPC tumours. My analysis revealed 607 differentially-expressed genes, some of which encoded other chemokines or protein regulating the immune system. In particular, I observed the upregulation of Cxcl10 and Cxcl12, and the downregulation of Gata3 and S100a4, which could explain the decrease in T cells in the TME of CKPC mice. In conclusion, although the lack of CX3CR1 modifies the TME in this genetic model of PDAC, these changes do not affect the lifespan or the response to chemotherapy.

Neutrophils are recognised to play a pivotal role at the interface between the innate and adaptive immune responses following their rapid recruitment to inflamed tissues and lymphoid organs. Whilst neutrophil trafficking through blood vessels has been extensively studied, the molecular mechanisms regulating their migration into the lymphatic system are still poorly understood. This thesis therefore aimed to investigate the mechanisms involved in neutrophil migration across the lymphatic endothelium during TNF- or Complete Freund's Adjuvant + antigen (CFA+Ag)-induced inflammation of cremaster muscles in vivo. This work revealed that TNF- or CFA+Ag-stimulation induces a rapid but transient entry of tissue-infiltrated neutrophils into lymphatic vessels, a response associated with the regulation and redistribution of the lymphatic endothelial cell glycocalyx. Interestingly, antigen sensitisation resulted in the production of endogenous TNF within cremaster muscles. Using anti-TNF blocking antibodies and mice deficient in both TNF receptors (p55 and p75), endogenous TNF was demonstrated for the first time to be involved in priming and triggering the migration of neutrophils into tissue-associated lymphatic vessels upon antigen challenge. Additionally, the use of chimeric mice exhibiting neutrophils deficient in both TNFRs demonstrated that TNF directly acts on leukocytes to induce neutrophil migration into lymphatic vessels. Furthermore, the results show that TNF-induced migration of neutrophils into the lymphatic system occurs in a strictly CCR7-dependent manner; blocking CXCR4 or CXCL1 signalling does not affect this response. Finally, both TNF- or CFA+AG-stimulation induced ICAM-1 up-regulation on lymphatic vessels, allowing neutrophils to crawl along the lumen; a response that was demonstrated to be TNF-dependent. These results have provided new insights into the mechanisms that mediate neutrophil migration into lymphatic vessels and their subsequent crawling within these vessels during inflammation. In particular, a new role for TNF as a key regulator of these processes has been demonstrated. Taken together, this work has highlighted potential and effective targets to manipulate the role of neutrophils in adaptive immune responses in vivo.

Toll-like receptor 4 (TLR4) is an important vertebrate innate immune receptor. TLR4 recognizes both endogenous and exogenous danger signals to trigger an NF-kB dependent inflammatory response. While exogenous danger signal recognition is an essential part of pathogen response by the innate immune system, endogenous danger signal recognition by TLR4 can lead to chronic and pathological inflammation. Understanding the differences in recognition of these two types of danger signals would allow for independent modulation of pathogen and host triggered inflammatory response through TLR4. Here, we examine the evolution of activation of TLR4 by two agonists, pathogen-derived lipopolysaccharide and host-produced S100A9. We show that these two types of signals evolved earlier than previously thought. We identified TLR4 cofactors MD-2 and CD14 in amphibians and fish, and validated that zebrafish TLR4 can recognize LPS. By contrast, we find that S100 activation evolved in the ancestor of amniotes. We identified an ortholog of S100A9 in birds and reptiles capable of activating TLR4. Using comparative immunology, we found that the requirements for LPS and S100A9 activation are different. In addition to our evolutionary studies, we used molecular approaches to probe if zinc binding to S100A9 is necessary for TLR4 activation. We found that activation of TLR4 by S100A9 occurs even in the absence of zinc. Finally, we describe how our evolutionary approach led to mechanistic hypotheses regarding TLR4 activation by both LPS and S100A9. This has led to ongoing projects in the Harms lab. This dissertation includes previously published and unpublished co-authored material. / 2021-04-30

Plasma cells, the effector stage of the B cell compartment, secrete large amounts of antibody. These cells arise in two waves during T-­‐dependent immune responses; an early wave (extrafollicular plasma cells) generate low-­‐affinity antibodies that provide a first line of defence against invading pathogens. Later, plasma cells emerge from the germinal centre reaction and secrete high-­‐affinity antibodies. These plasma cells have the capacity to migrate to the bone marrow, where they become established as long-­‐lived, non-­‐dividing plasma cells. Here, I show that plasma cells found in the bone marrow of young (5-­‐week-­‐old) mice had a turnover comparable to that seen in the spleen. Long-­‐lived plasma cells accumulated over the ensuing weeks until they came to dominate the bone marrow plasma cell compartment by 30-­‐weeks of age. This accumulation required MHC II, CD40 and a normal B cell receptor repertoire, implying that these cells are generated during T-­‐dependent immune responses. Secondly, I determine the signalling pathways required to generate splenic extrafollicular plasma cell responses in the T-­‐dependent response to sheep red blood cells (SRBC) and in bacterial infection with Salmonella. While T cell help, antigen recognition through the B cell receptor (BCR) and TLR signalling were required for maximal plasma cell responses to SRBC, in Salmonella infection TLR signalling was required for day 4 IgM plasma cell responses, whereas class-­‐ switched responses at day 8 required T cell help. The extrafollicular responses generated in Salmonella persisted for around 35 days, far greater than the 2-­‐3 days seen following SRBC immunisation. This was likely due to both antigen persistence causing the generation of new plasma cells, and the induction of cellular populations that produced the plasma cell survival factor APRIL. Thirdly, I document the failure of chronic immune responses to generate long-­‐ lived bone marrow plasma cells. This was accomplished by measuring the generation and survival of bone marrow plasma cells in models of rheumatoid arthritis (K/BxN mice), long-­‐term infection with Salmonella, and a direct comparison between acute and chronic delivery of the T-­‐dependent protein antigen NP-­‐KLH. In all cases, chronic immune responses generated few bone marrow plasma cells, ostensibly due to a failure to migrate to the organ. Finally, I show the depletion of bone marrow plasma cell populations caused by inflammatory episodes. This was observed in Salmonella infection, Schistosoma mansoni infection and immunisation with protein antigen plus adjuvants. This depletion mediated a reduction of antigen-­‐specific bone marrow plasma cell populations and serum antibody previously established by the secondary response to NP-­‐KLH.

Inflammation and oxidative stress are increasingly recognised as important independent mediators of preterm brain injury and have been implicated in the pathogenesis of cerebral palsy and cognitive impairment. Such exposures are common for the premature infant in whom infection and inflammatory morbidities occur in around 60%. Furthermore, many preterm infants require oxygen therapy and respiratory support due to lung immaturity. Epidemiological and experimental studies indicate that in addition to the independent effects of inflammation and extreme hyperoxia on the developing brain, inflammation preconditions the developing brain resulting in variable injury when exposed to subsequent hypoxia-ischaemia. However experimental studies employing exposure to more modest oxygen fluctuations are lacking. This thesis characterises a clinically relevant model of prematurity where the developing brain is exposed to low grade inflammation and oxygen fluctuation around a hyperoxic mean. We hypothesise that antenatal inflammation and postnatal oxygen fluctuation, both alone and in combination, have detrimental effects on developing white matter. Pregnant dams received intraperitoneal lipopolysaccharide (LPS) or saline on G18 and G19. Dams and their pups were then reared in room air or fluctuating hyperoxia (circa 10kPa) for seven days. We measured longitudinal brain and body growth in different experimental groups to 12 weeks. Whole brains were examined for mRNA expression of inflammatory cytokines (TNFα, IL-1β, IL-6 and IL-10) and markers of oxidative injury (iNOS, SOD2). To determine the effect of perinatal insults on developing white matter, we analysed the expression of myelin basic protein (MBP) and glial fibrillary acidic protein (GFAP) in the internal and external capsule. We also examined white matter tracts for differences in microglia (CD68), oligodendrocyte progenitor cells (NG2), oligodendroglial cells (Olig2) and cell death (cleaved caspase3). Behavioural studies (Morris Watermaze Test, Elevated Plus Test and Open Field Test) were undertaken at 12 weeks of age to detect any long-term functional difference between the groups. Antenatal inflammation reduces both brain and body growth at P7. This normalises by P14 unless this inflammatory insult has been followed by postnatal oxygen fluctuation, where brain and body growth restriction persists until P14. We defined our inflammatory response at P1 following antenatal inflammation and did not observe elevation of mRNA at P1. We demonstrated increased SOD2 at this time point, indicating a reparative process. At P7 we observed a significant reduction in the oxidative response following combined exposure to antenatal inflammation and postnatal oxygen fluctuation, indicating a potential limit to, or suppression of, the reparative process. In terms of white matter injury, antenatal inflammation reduces myelination at P7. There is no synergistic effect of inflammation and oxygen fluctuation on MBP immunohistochemistry at P7. However, MBP mRNA expression is increased in pups exposed to both insults compared to those exposed to inflammation alone suggesting that the oxygen fluctuation may stimulate MBP production in response to oxidative injury. MBP mRNA levels and protein expression have all normalised by P14. We observed a reduction in total cell number in the external capsule and corpus callosum in the dual insult group, without an increase in caspase. In keeping with other studies we detected no effect of our perinatal insults on NG2+ve oligodendrocytes. Olig2+ve cell numbers were also consistent between experimental groups. In further characterisation of the cellular response, antenatal inflammation followed by postnatal oxygen fluctuation resulted in a decrease in GFAP mRNA at P7, an effect which was reversed and significantly increased by P14 suggesting delayed activation of the innate immune system. No difference was observed in microglial numbers between experimental groups. There was however, increased microglial cell death (CD68 + caspase) in the group exposed to antenatal inflammation. When this insult was combined with postnatal oxygen fluctuation there was a comparative decrease in microglial cell death, which may reflect an earlier peak of microglial cell death, due to an increased and sustained inflammatory stimulus. Morris Watermaze testing demonstrated that pups exposed to both insults took longer than controls to locate the hidden platform on day 1, which is a measure of spatial learning. The Elevated Plus Test and Open Field Test demonstrated that pups exposed to both insults were less anxious and took more risks than pups exposed to single insults. In conclusion, within a clinically relevant preterm model, antenatal inflammation transiently disrupts both brain and body growth and myelination of the motor tracts of the developing brain. Moreover, when combined with postnatal oxygen fluctuation, detrimental effects on growth are amplified and sustained. Decreased cell numbers are also observed within white matter tracts. In terms of long term functionality, these pups display disinhibition of behaviour as young adults. Collectively, this thesis demonstrates that synergistic actions of common low-grade perinatal insults may alter normal neurodevelopment, and that this may carry a risk of neurodevelopmental sequelae for preterm infants.