Les amibes libres sont des protozoaires retrouvés dans de nombreux environnements où ils ingèrent par phagocytose des bactéries, des champignons, des virus ou d'autres protozoaires. Le modèle d'étude principal de cette thèse, divisée en deux grandes parties, a été Acanthamoeba castellanii. La première partie de la thèse a concerné l'étude de la préférence trophique des amibes, en présence de différents micro-organismes. Parmi ceux-ci, deux bactéries, Klebsiella pneumoniae et Staphylococcus aureus, se sont montrées les plus attractives pour les protozoaires étudiés. Des extraits bactériens ont été fractionnés et leur étude a permis de mettre en évidence la nature protéique des composés chimioattractifs impliqués dans ce dialogue intergenre. Certaines données de la littérature ont rapporté les similitudes entre A. castellanii et d'autres cellules phagocytaires que sont les macrophages. La seconde partie de la thèse a permis de comparer les activités de phagocytose d'A. castellanii et de la lignée macrophagique Thp-1 vis-à-vis de quatre micro-organismes : le champignon filamenteux Aspergillus fumigatus, les bactéries Klebsiella pneumoniae et Staphylococcus aureus, et un Adénovirus sérotype B3. L'influence des deux types de cellules phagocytaires sur la croissance des micro-organismes a également été étudiée. Ces travaux ont permis de mettre en évidence des différences de comportements des amibes libres par rapport aux macrophages vis-à-vis de micro-organismes pathogènes, montrant qu'il n'est pas toujours possible d'extrapoler les résultats d'études amibes libres/micro-organismes aux relations macrophages/micro-organismes. / Free living amoebae (FLA) are protoza found in various environments where they can feed by phagocytosis on bacteria, fungi, viruses or other protozoa. Acanthamoebae castellanii was used as the main model in this thesis, divided in two parts. The first part of the thesis relied on the trophic preference of amoebae, in presence of different microorganisms. Amongst them, two bacteria, Klebsiella pneumoniae and Staphylococcus aureus, appeared as the most attractive for the studied protozoa. Bacterial extracts have been fractionned and their study has shown the protein nature of the chemoattractants involved in this interspecies crosstalk.Literature data have reported similarities between A. castellanii and other phagocytic cells such as macrophages. The second part of the thesis allowed us to compare phagocytic activities of A. castellanii and Thp-1 macrophagic cells towards four microorganisms: the filamentous fungus Aspergillus fumigatus, the bacteria Klebsiella pneumoniae and Staphylococcus aureus and an Adenovirus B3 serotype. The influence of the two phagocytic cells on the microorganisms' growth has also been investigated. This has evidenced the behavior differences between FLA and macrophages towards pathogenic microorganisms, showing that results obtained by studying amoebae and microorganisms relationships could not be extrapolated in all cases to the relationships between macrophages and microorganisms.

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are fatal neurodegenerative diseases that affect several species, such as scrapie in sheep or goats and CJD in humans. In several species, neurological disease is preceded by TSE agent accumulation in lymphoid tissues prior to neuroinvasion. While oral transmission is considered the most common route for scrapie, transmission can also occur through lesions to the skin or mucosa, for example in the mouth or gastrointestinal tract due to rough feed, or birth associated skin damage. Scrapie has also been experimentally transmitted through skin scarification in mice. Following scrapie infection via skin scarification, PrPSc accumulates in the draining lymph node (LN) before spreading to other organs in the lymphoreticular system. It is not yet known by what means the scrapie agent is transported from the skin to the draining LN. Dendritic cells (DCs) in the skin have been found to transport viruses, such as HIV or Dengue, from the skin, thereby raising the question whether DCs or Langerhans cells (LCs), located within the epidermis, play a role in the uptake and transport of the TSE agent from the skin to the draining LN. CD11c is a cell surface marker traditionally used to identify or isolate DCs from other cell types. Mice and rats are naturally resistant to Diphtheria toxin (DTX). A transgenic mouse line was created where the Diphtheria toxin receptor (DTR) was expressed on CD11c+ cells. The presence of this receptor on CD11c+ cells allowed for the temporary conditional depletion of CD11c+ cells following a single injection of DTX. The cells repopulate the tissues within a time frame specific to the tissues the cells are located in. These mice were used to determine whether the absence of CD11c+ cells at the time of scrapie infection via the skin had an effect on the early accumulation of PrPSc within the lymphoid tissues and on disease progression. Immunohistochemical analysis demonstrated that early PrPSc accumulation in the draining LNs was delayed following depletion of CD11c+ cells, indicating that their potential role in the transport of the scrapie agent from the skin. Scrapie incubation period was not affected by the absence of the CD11c+ cells at the time of infection. Recent findings show that CD11c is not exclusive to DCs and is also expressed on macrophage populations. Following DTX-mediated depletion, DCs repopulate the tissues much faster than CD11c+ macrophages. Scrapie infection was carried out in the skin in DTX treated mice after DCs had repopulated the tissues but before macrophage numbers had returned, to determine whether macrophages rather than DCs played a role in the early accumulation of PrPSc in the draining LNs. No differences in PrPSc accumulation were observed in mice depleted of macrophages compared to controls and there was no effect on disease incubation period. Another transgenic mouse line was used, where DTX expression on langerin+ cells (LCs and langerin+ DCs in the dermis), allowed for their temporary depletion through DTX treatment. Following langerin+ cell depletion, increased PrPSc accumulation was observed in the draining LNs 7 weeks post infection, but did not affect the incubation period of disease. These results indicate that the absence of LCs somehow accelerated PrPSc accumulation, and that LCs might play a preventative role in early stages after infection. Histopathological analysis was used to complement microarray studies aimed to determine what immune responses were associated with scarification and DTXmediated depletion of cells within the skin and whether these responses might be linked to disease transmission. DCs and LCs in the skin appear to play different roles in the early stages following scrapie infection via the skin, but the lack of effect on incubation period does not rule out the involvement of other cell types or cell-free mechanisms of scrapie agent spread from the skin.

A promoção a amamentação representa uma importante estratégia de saúde pública no manejo do sobrepeso e obesidade mundial. É possível que os hormônios reguladores do metabolismo energético, como a adiponectina, leptina e melatonina do colostro humano, possa beneficiar o sistema imunológico do lactente e minimizar os impactos ocasionados pelo excesso de peso materno pré-gestacional. Dado que, esses hormônios também possuem ação imunomoduladora. Assim, mudanças nas concentrações desses hormônios, podem comprometer a atividade funcional das células mononucleares (MN) do colostro humano e contribuir para o aumento de infecções neonatais. Por isto, o objetivo desta pesquisa foi analisar a atividade funcional dos fagócitos MN do colostro de mulheres com excesso de peso pré-gestacional, na ausência e presença de adiponectina, leptina e melatonina. As amostras de colostro foram coletadas de 109 doadoras saudáveis e foram divididas em dois grupos: grupo controle e grupo com excesso de peso. O colostro foi centrifugado para obtenção do botão celular e sobrenadante. O sobrenadante foi utilizado para dosagem de melatonina, quantificada por ELISA. As células MN foram utilizadas no ensaio de fagocitose, por citometria de fluxo, e a produção de espécies reativas de oxigênio (EROS), cálcio intracelular e apoptose foram realizadas por fluorimetria. Foram consideradas diferenças significativas quando p<0,05. O colostro de mulheres com excesso de peso pré-gestacional apresentou uma maior concentração de melatonina (p<0,05). Os fagócitos MN do grupo excesso de peso teve um menor índice de fagocitose (p<0,05). No entanto, os estímulos foram capazes de restaurar a atividade fagocítica para este grupo (p<0,05). A adiponectina+leptina foi o estímulo que desenvolveu uma resposta mais efetiva, com restauração dos níveis de EROS, manutenção do cálcio intracelular e elevação do índice de apoptose para o grupo com excesso de peso (p<0,05). Os dados em conjunto reforçam a hipótese de que amamentação é benéfica para a saúde da criança. A manutenção dos níveis endógenos de adiponectina, leptina e melatonina pode aumentar a proteção e diminuir os índices de infecção neonatais, em filhos de mulheres com excesso de peso. Assim, políticas públicas que apoiam o controle de peso pré-gestacional devem ser encorajadas / Breastfeeding promotion represents an important public health iniciative in worldwide overweight and obesity management strategies. It is possible that the hormones regulating energy metabolism, such as adiponectin, leptin and melatonin of human colostrum can benefit the infant\'s immune system and minimize the impacts caused by pre-gestational maternal overweight. As these hormones also have immunomodulatory action, changes in their concentrations can affect the functional activity of mononuclear cells of human colostrum and contribute to the increase of neonatal infections. Therefore, the aim of this study is to analyze the functional activity of colostrum mononuclear phagocytes in women with pregestational overweight, with absence or presence of adiponectin, leptin and melatonin. Colostrum samples collected from 109 healthy donors were divided into two groups: the control group and the high body mass index (BMI) group. Colostrum samples were centrifuged to obtain the cell button and supernatant. The supernatant was used for melatonin dosing performed by ELISA, mononuclear cells used to phagocytosis assay, by flow cytometry and production of reactive species of oxygen, intracellular calcium and apoptosis assays were performed by fluorimetry using plate reader. Statistically significant differences were considered when p <0.05. Colostrum of pre-gestational high BMI group had higher concentration of melatonin (p <0.05). Mononuclear phagocytes of high BMI group had a lower index of phagocytosis (p <0.05). However, the stimuli restored the phagocytic activity for high BMI group (p <0.05). Adiponectin+leptin was the stimulus that developed a more effective response, with restoration of reactive oxygen species levels, maintenance of intracellular calcium and elevation of apoptosis index (p < 0.05) in the high BMI group. These data reinforce that breastfeeding is beneficial to child\'s health and maintaining endogenous levels of adiponectin, leptin and melatonin may increase protection and decrease neonatal infection rates in children of women with high BMI. Thus, public policies that support pre-gestational weight control should be encouraged.

O formaldeído (FA) é um poluente ambiental gerado pela indústria, originando-se também pela queima de tabaco, gasolina, álcool e GLP. É irritante de vias aéreas; a exposição ao FA pode contribuir para mediar a inflamação alérgica pulmonar (IAP) a outros antígenos. Neste estudo analisamos o estado funcional de fagócitos do pulmão e da medula óssea de ratos Wistar machos após inalação de FA (1%, 90 min/dia, 3 dias) e a seguir submetidos a IAP (sensibilizados e desafiados com ovoalbumina), bem como a expressão de moléculas de adesão. Sobrenadantes de culturas de pulmão, de fagócitos pulmonares e da medula óssea foram coletados após 1, 4 ou 24 h. Verificou-se em ratos submetidos a IAP que, no pulmão, a exposição prévia ao FA aumentou NO2, H2O2, LTB4, TXB2, PGE2, IL-1<font face=\"symbol\">b, TNF-<font face=\"symbol\">a e diminuiu IL-10; na medula óssea, aumentou NO2 e PGE2, e diminuiu H2O2, LTB4, TXB2, IL-1<font face=\"symbol\">b e IL-10. A interação FA/OVA reduziu a expressão de ICAM-1, VCAM-1 e PECAM-1. Em conclusão, o FA medeia alterações na atividade funcional de fagócitos envolvidos com o desenvolvimento da asma. / Formaldehyde (FA) is an ambiental pollutant generated in industry and by burning of tobacco, alcohol, gasoline and LPG. As an airways irritant agent, the exposure to it may affect the modulation of allergic lung inflammation (ALI) triggered by unrelated antigens. We studied the functional activity of lung phagocytes and bone marrow cells from male Wistar rats previously subjected to FA inhalation (1%, 90 min/day, 3 days) and then subjected to ALI (ovalbumin sensitized and challenged), as well as the expression of adhesion molecules. Supernatants of lung explants, lung phagocytes and bone marrow cells were collected after 1, 4 or 24 h upon or not LPS or PMA stimulation. After FA inhalation, ALI increased NO2, H2O2, LTB4, TXB2, PGE2, IL-1<font face=\"symbol\">b, TNF-<font face=\"symbol\">a and decreased IL-10 in the lung, whereas enhanced NO2 e PGE2 and reduced H2O2, LTB4, TXB2, IL-1<font face=\"symbol\">b and IL-10 in bone marrow cells. The interaction FA/OVA decreased the expression of ICAM-1, VCAM-1 e PECAM-1. In conclusion, FA significantly alters the functional activity of phagocytes involved with asthma induction.

Dendritic cells (DCs) comprise a distinct lineage of potent antigen-presenting mononuclear phagocytes that serve as both mediators of innate immune responses and key facilitators of the adaptive immune response. DCs play both immunogenic and tolerogenic roles through their dual ability to elicit pathogen-specific T cell immunity as well as induce regulatory T cell (Treg) responses to promote tolerance in the steady state. The aim of the work presented here is to examine the normal regulatory mechanisms of DC development and function, starting with the dissection of mechanisms behind an aberrantly activated developmental pathway, followed by the exploration of new mechanisms governed by two candidate transcription factors. The first chapter of the thesis focuses on the growth factor receptor Flt3, an essential regulator of normal DC development in both mice and humans, and concurrently one of the most commonly mutated proteins found in acute myeloid leukemia (AML). We investigated the effect of its most common activating mutation in AML, the Flt3 internal tandem duplication (Flt3-ITD), and found that this mutation caused a significant cell-intrinsic expansion of all DC populations. This effect was associated with an expansion of Tregs and the ability to dampen self-reactivity, with an inability to control autoimmunity in the absence of Tregs. Thus, we describe a potential mechanism by which leukemia can modulate T cell responses and support Treg expansion indirectly through DCs, which may compromise immunosurveillance and promote leukemogenesis. The subsequent chapters explore the basic molecular mechanisms of DC development by using Flt3 expression as a guide to uncover new candidates involved in the DC transcriptional program. We show that Myc family transcription factor, Mycl1, is largely dispensable for DC development and function, contrary to recent published findings that propose a role in proliferation and T cell priming. On the other hand, we find that conditional deletion of our second candidate gene, an Ets family transcription factor, has diverse effects on DC development, monocyte homeostasis, and cytokine production. Overall, our studies highlight an unexpected molecular link between DC development and leukemogenesis, and elucidate novel mechanisms controlling DC differentiation and function.

O colostro bovino contém fatores imunológicos, como imunoglobulinas, leucócitos e citocinas, absorvidos pela mucosa intestinal do neonato até 48 horas de vida, no entanto, pouco se conhece sobre a função de alguns desses componentes, como as citocinas, participantes da resposta imune inata e adaptativa. Acredita-se que estas substâncias possuem papel importante na imunidade dos neonatos nos seus primeiros dias de vida. Assim, os objetivos específicos desta pesquisa foram: determinar as concentrações das citocinas IL-1&#946, IL-6, IFN-&gamma; e TNF-&alpha; no soro sanguíneo e colostro de fêmeas bovinas da raça Holandesa; verificar a liberação de citocinas pelas células mononucleares do colostro e sangue bovino &quot;in vitro&quot; antes e após a estimulação com Escherichia coli enterotoxigênica (ECET); avaliar a transferência das citocinas IL-1&beta;, IL-6 e TNF-&alpha; do colostro aos bezerros neonatos, por meio da determinação das concentrações destas citocinas no soro sanguíneo dos bezerros, durante os quinze primeiros dias de vida. O trabalho foi realizado em duas etapas, em duas propriedades distintas: (1) avaliação do soro sanguíneo e colostro de primeira ordenha proveniente de 22 fêmeas; (2) avaliação das citocinas sanguíneas de 11 bezerros, antes e após a mamada de colostro. Nesta pesquisa foi possível determinar as medianas da concentração de citocinas IL-1&beta;, IL-6, IFN-&gamma; e TNF-&alpha; no colostro bovino e soro sanguíneo, correspondente a 70,5 e 41,5; 86,1 e 13,5; 41 e 57,9; 139,9 e 20,8 pg/mL, respectivamente, verificando menores valores de IFN-&gamma; no colostro e TNF-&alpha; e IL-6 no soro sanguíneo. Observou-se diferença entre as citocinas no colostro e soro sanguíneo para a TNF-&alpha;. Observou-se produção de citocinas pelas células do colostro e sangue das mães mediante liberação espontânea e pela ECET com tendência ao aumento dessa produção entre os períodos de incubação celular e pela estimulação com ECET. A avaliação do soro dos bezerros mostrou ausência das citocinas IL-1&beta;, IL-6 e TNF-&alpha; antes da ingestão de colostro, que atingiram pico após 48 horas de vida. Os valores médios das concentrações de citocinas presentes no soro das vacas e novilhas foram de 98,3; 88,4; 53,5 e 235,9 pg/mL e 144,5; 94,5; 83,9 e 116,2 pg/mL, para IL-1&beta;, IL-6, IFN-&gamma; e TNF-&alpha;, respectivamente. Os valores médios das concentrações de citocinas (pg/mL) presentes no colostro das vacas e novilhas foram de 97,4; 21,3; 143,3 e 35,1 pg/mL e 69,5; 6,4; 51,9 e 16,32 pg/mL, para as citocinas IL-1&beta;, IL-6, IFN-&gamma; e TNF-&alpha;, respectivamente. Quando se comparou os dois grupos analisados verificou-se que os valores médios de IFN-&gamma; e TNF-&alpha; foram significativamente maiores nas vacas. Assim, com base nos resultados desta pesquisa foi possível: (a) determinar a concentração de citocinas do soro sanguíneo e colostro de fêmeas bovinas; (b) verificar a produção de citocinas pelas células do soro e colostro das vacas, verificando-se diferentes perfis nestas duas regiões; (c) verificar a absorção das citocinas do colostro pelo neonato bovino; (d) verificar que as vacas possuem maiores concentrações de citocinas IFN-&gamma; e TNF-&alpha; no colostro, quando comparadas às novilhas; (e) não há diferenças entre a concentração das citocinas do colostro obtidas em diferentes quartos mamários. / Bovine colostrum contains immunological factors, such as immunoglobulins, leukocytes and cytokines, which are absorbed by the intestinal mucous membrane of the neonate up to 48 hours of life. However, little is known about the function of some of these components, such as cytokines, which take part in innate and adaptive immune responses. It is believed that these substances have important roles in neonate immunity on their first days of life. Therefore, the specific objectives of this study were: to determine the concentration of cytokines IL-1&beta;, IL-6, IFN-&gamma; and TNF-&alpha; in serum and colostrum of Holstein cows; to assess the in vitro release of cytokines by mononuclear cells of colostrum and blood before and after stimulation with enterotoxigenic Escherichia coli (ECET); to evaluate IL-1&beta;, IL-6 and TNF-&alpha; transfer from colostrum to neonate calves by determining cytokine concentrations in calf blood during the first 15 days of life. The study was carried out in two stages, in different farms: (1) evaluation of blood and first milking colostrum in 22 females; (2) evaluation of blood cytokines of 11 calves, before and after colostrum intake. In this study, it was possible to determine the medians of IL-1&beta;, IL-6, IFN-&gamma; and TNF-&alpha; concentration in blood and colostrum as equal to 70.5 and 41.5; 86.1 and 13.5; 41 and 57.9; 139.9 and 20.8 pg/mL, respectively. The lowest values of IFN-&gamma; were observed in colostrum, and of TNF-&alpha; and IL-6, in serum. TNF-&alpha; concentration was different in serum and in blood. It was observed colostrum and blood cells of the cows produced cytokines spontaneously and by means of ECET, with a tendency to increase production in periods of cell incubation and stimulation with ECET. Evaluation of calf serum showed absence of cytokines IL-1&beta;, IL-6 and TNF-&alpha; before colostrum ingestion, and these cytokines reached a peak after 48 hours of life. Mean values for cytokine concentration in the serum of cows and heifers were 98.3; 88.4; 53.5 and 235.9 pg/mL, and 144.5; 94.5; 83.9 and 116.2 pg/mL, for IL-1&beta;, IL-6, IFN-&gamma; and TNF-&alpha;, respectively. Mean values for cytokine concentration in the colostrum of cows and heifers were 97.4; 21.3; 143.3 and 35.1 pg/mL, and 69.5; 6.4; 51.9 and 16.32 pg/mL, for IL-1&beta;, IL-6, IFN-&gamma; and TNF-&alpha;, respectively. When the two groups were analyzed, it was observed that mean de IFN-&gamma; and TNF-&alpha; were significantly greater in the cows. Thus, based on the results of this study, it was possible to: (a) determine the concentration of cytokines in serum and colostrum of cows; (b) assess cytokine production by cells of cow serum and colostrum, observing different profiles in the two samples; (c) observe cytokine absorption from colostrum by the calves; (d) assess that cows show greater concentrations of IFN-&gamma; and TNF-&alpha; in the colostrum, when compared with heifers; (e) that there are no differences between cytokine concentrations observed in the different quarters.

Terminally differentiated B cells are responsible for antibody generation, a key component of adaptive immunity. IgG antibodies play an important role in defence against infection but can be pathogenic in some autoimmune diseases and in solid organ transplantation. In addition to antibody generation, there is increasing interest in the antibody-independent functions of B cells, including their ability to regulate immune responses via the production of IL10. In this thesis I firstly explored the therapeutic potential of belimumab, an anti-BLyS antibody, in an experimental medicine study in kidney transplant recipients. The rationale for this study was based on published studies showing that B cells activate alloreactive T cells and secrete human leukocyte antigen (HLA) and non-HLA antibodies that negatively affect graft function and survival, but may also play a protective role by regulating alloimmune responses promoting transplant tolerance. B-Lymphocyte Stimulator (BLyS) is a cytokine that promotes B cell activation and survival. We performed the first randomized controlled trial using belimumab as early maintenance immunosuppression in kidney transplantation. In belimumab-treated subjects, we demonstrate a reduction in naïve and activated memory B cells, plasmablasts, IgG transcripts in peripheral blood and new antibody formation as well as evidence of reduced CD4 T cell activation and of a skewing of the residual B cell compartment towards an IL10-producing regulatory phenotype. This experimental medicine study highlights the potential of belimumab as a novel therapeutic agent in transplantation. In the second part of my project I performed a preclinical study investigating the potential efficacy of bromodomain inhibitors in reducing antibody-mediated immune cell activation. Immune complexed antigen can activate mononuclear phagocytes (MNP), comprising macrophages and dendritic cells (DCs), via ligation of Fc gamma receptors (FcγR), that bind the Fc region of IgG. FcγR-dependent MNP activation results in profound changes in gene expression that mediate antibody effector function in these cells. The resulting inflammatory response can be pathological in the setting of autoimmune diseases, such as systemic lupus erythematosus and in antibody-mediated rejection in transplantation. BET proteins are a family of histone modification 'readers' that bind acetylated lysine residues within histones and function as a scaffold for the assembly of complexes that regulate gene transcription. Bromodomain inhibitors (I-BET) selectively inhibit the transcription of a subset of inflammatory genes in macrophages following toll-like receptor stimulation. Since MNPs make a key contribution to antibody-mediated pathology, we sought to determine the extent to which I-BET inhibits macrophage and DC activation by IgG. We show that I-BET delays phagolysosome maturation associated with build-up of immune complex (IC) whilst selectively inhibiting IC induced cytokine production. I-BET changed MNP morphology, resulting in a less adherent phenotype, prompting an assessment of its impact on DC migration. In vitro, in a three-dimensional collagen matrix, IgG-IC induced augmentation of DC chemotaxis to chemokine (C-C motif) ligand 19 (CCL19) was abrogated by the addition of I-BET. In vivo, two photon imaging showed that systemic I-BET treatment reduced IC-induced dermal DC mobilisation. Tissue DCs and transferred DC also had reduced migration to draining lymph nodes following I-BET treatment. These observations provide mechanistic insight into the potential therapeutic benefit of I-BET in the setting of antibody-associated inflammation.

Thesis (Ph. D.)--University of Nevada, Reno, 2000. / Includes bibliographical references. Online version available on the World Wide Web.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Thesis (Ph.D. in Immunology) -- University of Colorado Denver, 2007. / Typescript. Non-Latin script record Includes bibliographical references (181-196). Free to UCD affiliates. Online version available via ProQuest Digital Dissertations;