Submitted by Ana Maria Fiscina Sampaio (fiscina@bahia.fiocruz.br) on 2014-02-17T17:49:04Z No. of bitstreams: 1 Cintia Figueiredo de Araújo Investigação sobre uma atividade...2013.pdf: 1673861 bytes, checksum: b9ab47b2dff7a275b8deca0557230323 (MD5) / Made available in DSpace on 2014-02-17T17:49:04Z (GMT). No. of bitstreams: 1 Cintia Figueiredo de Araújo Investigação sobre uma atividade...2013.pdf: 1673861 bytes, checksum: b9ab47b2dff7a275b8deca0557230323 (MD5) Previous issue date: 2013 / Fundação Oswaldo Cruz. Centro de Pesquisa Gonçalo Moniz. Salvador, BA, Brasil / Os protozoários do gênero Leishmania são parasitos intracelulares que causam um conjunto de doenças, as leishmanioses, em milhões de pessoas no mundo. As leishmanias secretam moléculas que modulam o sistema imune do hospedeiro, contribuindo para o estabelecimento da infecção por interferirem na atividade microbicida do macrófago. Os objetivos desse trabalho foram identificar proteínas de Leishmania com atividade imunomoduladora e caracterizar essa imunomodulação. No trabalho foram avaliados os efeitos potenciadores de polipeptídeos da cinesina recombinante de Leishmania infantum, do extrato de Leishmania braziliensis (ELb) e de frações purificadas do extrato de Leishmania amazonensis (ELa), tratados ou não com inibidores de serina ou cisteína proteases, sobre a infecção por L. braziliensis, em camundongos BALB/c. Os animais foram acompanhados semanalmente, durante 6 semanas pós infecção, para a mensuração dos tamanhos das lesões. Após a eutanásia foi realizada a diluição limitante das lesões, a quantificação das concentrações de IL-4 e IL-10 da cultura em leucócitos estimulados com anti-CD3 e a semiquantificação de IgG1 e IgG2a do soro. Frações do ELa foram processadas por técnicas de espectrometria de massas para identificação de proteínas. Foi observado que frações de pesos moleculares aparentes de 28, 36, 45, 68 kDa do ELa foram capazes de potenciar a infecção por L. braziliensis, assim como um polipeptídeo da cinesina recombinante de L. infantum com motivos repetitivos e ELb contendo 5 μg de proteína. Quando as frações de 28 e 68 kDa foram tratadas com os inibidores de serina proteases, elas perderam a capacidade de potenciar a infecção por L. braziliensis, apesar de não terem sido identificadas serina proteases nessas frações por espectrometria de massas. / Leishmania are intracellular parasites that cause a group of diseases, the leishmaniases. Millions of people worldwide are infected with those protozoa. They secrete molecules that modulate the host immune system, allowing the establishment of the infection by interfering in the microbicidal activity of macrophages. The aims of this study were to identify proteins of Leishmania with immunomodulatory activity and characterize this immunomodulation. In this study the infection-enhancing effects of recombinant kinesin polypeptides of Leishmania infantum, Leishmania braziliensis extract (LbE) and purified fractions of the Leishmania amazonensis extract (LaE), treated or not with inhibitors of serine or cysteine proteases, on BALB/c mice infected with L. braziliensis. Animals were monitored weekly for 6 weeks post-infection for measuring the size of the lesion and after euthanasia were carried out at limiting dilution of the lesion, dose of IL-4 and IL-10 from culture supernatant of cells in draining lymph nodes lesion and determination of IgG1 and IgG2a serum. Fractions were processed by techniques of mass spectrometry for protein identification. Iit was seen that fractions of LaE with apparent molecular weights of 28, 36, 45, and 68 kDa were able to excarcebate the cutaneous disease caused by L. braziliensis, as were a recombinant kinesin polypeptide of L. infantum with repetitive motifs and LbE at a dose of 5 μg. However, when the fractions of 28 and 68 kDa were treated with inhibitors of serine proteases, they lost their ability to potentiate the infection by L. braziliensis, despite the fact that peptides of serine proteases were not identified in those fractions by mass spectrometry.

Made available in DSpace on 2014-06-11T19:27:56Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-18Bitstream added on 2014-06-13T20:17:30Z : No. of bitstreams: 1 bachiega_tf_me_botfm.pdf: 459615 bytes, checksum: ade6efe273ffa9cabd596ec413f8732b (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Nosso grupo tem se dedicado à investigação das ações biológicas da própolis, alecrim-do-campo, capim-limão e cravo-da-Índia. A própolis tem despertado a atenção dos pesquisadores em virtude de suas inúmeras propriedades biológicas, e o alecrim-do-campo é uma das principais fontes deste apiterápico em nossa região. Já o capim-limão e o cravo-da-Índia têm sido pouco avaliados no tocante à sua ação imunomoduladora. O objetivo deste trabalho foi avaliar o efeito imunomodulador do extrato e respectivos compostos isolados da: própolis (ácidos cumárico e cinâmico), do alecrim-do campo (ácido cafeico), do cravo-da-Índia (eugenol) e do capim-limão (citral) sobre a produção de citocinas (IL-1, IL-6 e IL-10) por macrófagos peritoneais de camundongos BALB/c. Em protocolos com LPS, macrófagos foram incubados ora com os produtos naturais supracitados em diferentes concentrações e posteriormente desafiados com LPS; ora desafiados com LPS e posteriormente incubados com os produtos naturais. A dosagem das citocinas foi realizada através da técnica de ELISA. A própolis exerceu ação moduladora sobre a resposta imune e inflamatória, e os ácidos cinâmico e cumárico podem estar envolvidos em sua ação imunomoduladora. O alecrim-do-campo e o ácido cafeico também demonstraram efeito imunomodulador quanto à produção de citocinas. O capim-limão exerceu efeito inibitório sobre a produção de citocinas, sendo este efeito mais pronunciado em ensaios com o citral. Resultados semelhantes foram observados com o cravo-da-Índia e o eugenol. Nossos resultados sugerem que o potencial imunomodulador dos produtos naturais merece ser melhor explorado em futuras investigações, avaliando sua eficiência em doenças inflamatórias / Our group has been investigating the biological action of propolis, “alecrim-do-campo”, lemongrass and clove. Propolis has attracted the researchers’ attention due to its several biological properties, and “alecrim-do-campo” is its main vegetal source in our region. However, little is known concerning lemongrass and clove immunomodulatory action. The goal of this work was to evaluate the immunomodulatory effect of the following extracts and isolated compounds: propolis (coumaric and cinnamic acids), “alecrim-do-campo” (caffeic acid), clove (eugenol) and lemongrass (citral) on cytokines production (IL-1, IL-6 and IL-10) by peritoneal macrophages of BALB/c mice. In LPS protocols, macrophages were incubated either with natural products in different concentrations and then challenged with LPS; or with LPS and then incubated with the natural products. Cytokine concentrations were measured by ELISA. Propolis exerted a modulatory action on the immune and inflammatory response and cinnamic and coumaric acids may be involved in its immunomodulatory action. “Alecrim-do-campo” and caffeic acid also exerted an immunomodulatory action on cytokines production. Lemongrass showed an inhibitory action on cytokines production, mainly in the assays with citral. Similar results were found using clove and eugenol. Our results suggest that the immunomodulatory potential of the natural products should be investigated in further studies, evaluating their efficacy in inflammatory diseases

Despite the success of modern medicine in treating infections, infectious diseases remain a major source of morbidity and mortality worldwide. The evolution of antibiotic resistant strains of bacteria means that new innovations in therapeutics must be pursued to combat this emerging threat. A novel approach is to utilize the anti-infective properties of endogenous host defense peptides by creating smaller synthetic peptides with enhanced protective activities. Some of these peptides directly kill bacteria and many display varied immunomodulatory activities, enhancing the host innate immune response to more effectively clear an infection. Here I examined the efficacy of several synthetic peptides in a murine model of invasive bacterial infection, induced by the Gram positive bacterium Staphylococcus aureus. Several peptides were able to significantly reduce peritoneal bacterial load in vivo by up to 4-logs relative to the controls, either through direct antibacterial killing or immunomodulatory activity. The latter class was studied in more detail; in particular, the peptides IDR-1 and 1002 displayed significant immunomodulatory effects in vivo. Both peptides were able to significantly induce the proinflammatory chemokines MCP-1, RANTES and KC, as well as increased recruitment of neutrophils and monocytes to the site of infection. These effects were not dependent on live bacteria, as heat inactivated S. aureus was also able to induce chemokines and cell migration. Mice that had been depleted of macrophages did not respond to peptide treatment, indicating that macrophages are an important effector cells through which immunomodulatory peptides counter infections. These results suggest that synthetic peptides have the potential to become a viable treatment option for bacterial infections. / Science, Faculty of / Microbiology and Immunology, Department of / Graduate

These studies evaluated the effects treatment with glucan phosphate, a soluble polysaccharide immunomodulator, on the inflammatory response induced by burn injury and on resistance to Pseudomonas aeruginosa burn wound infection. Mice were exposed to 35% total body surface area burns and were resuscitated with lactated Ringer's (LR) solution alone or LR supplemented with glucan phosphate (40 mg/kg). Glucan phosphate treatment attenuated burn-induced expression of interleukin (IL)-1β, IL-6, and IL-10 mRNAs in spleen, lung, and heart. Plasma concentrations of IL-1β, IL-6, macrophage inflammatory protein (MIP)-2, and IL-10 were also decreased in burned mice treated with glucan phosphate compared with vehicle-treated controls. Early postburn mortality was not significantly different between control (20%) and glucan phosphate-treated (10%) mice, but there was a small improvement in acid-base balance in the glucan phosphate-treated group. Mice received a second injection of glucan phosphate or LR on day 4 postburn and were infected by topical application of P. aeruginosa to the burn wound on day 5. Glucan phosphate treatment significantly improved survival in mice exposed to P. aeruginosa burn wound infection. The improved survival correlated with lower bacterial burden in the burn wound, attenuated production of proinflammatory cytokines, and enhanced production of Th1 cytokines. These studies show that glucan phosphate treatment attenuates burn-induced inflammation and increases resistance to P. aeruginosa burn wound infection in an experimental model of burn injury.

Glucans are microbial cell wall carbohydrates that are shed into the circulation of patients with infections. Glucans are immunomodulatory and have structures that are influenced by bacterial or fungal species and growth conditions. We developed a method to covalently label carbohydrates with a fluorophore on the reducing terminus, and used the method to study the pharmacokinetics following intravenous administration of three highly purified and characterized glucans (glucan phosphate, laminarin and scleroglucan) that varied according to molecular size, branching frequency and solution conformation. Elimination half-life was longer (3.8±0.8 vs. 2.6±0.2 and 3.1±0.6 h) and volume of distribution lower (350±88 ml/kg vs. 540±146 and 612±154 ml/kg) for glucan phosphate than for laminarin and scleroglucan. Clearance was lower for glucan phosphate (42±6 ml/kg h) than for laminarin (103±17 ml/kg h) and scleroglucan (117±19 ml/kg h). Since plasma levels at steady state are inversely related to clearance, these differences suggest that pharmacokinetics could favor higher blood levels of glucans with certain physicochemical properties.

The numerous benefits associated with natural products isolated from the environmental sources, including soil bacteria, plants and fungi, are long known and well appreciated. Interestingly, the immense number of microorganisms that reside within our bodies and whose cell counts greatly outnumber our own represents a potentially new and practically untapped reservoir of bioactive compounds. With the advent of next generation sequencing we are only now starting to realize the complexity and biological diversity of the human microbiome. With this ever-increasing flow of genomic information, more bioactive potential in these microbes can be identified. For instance, biosynthetic assembly lines responsible for the production of two largest classes of bioactive compounds, polyketides and nonribosomal peptides, can be readily identified within the microbial genomes, providing us with a view of their bioactive profiles. In addition to the identification of biosynthetic assembly lines, the building blocks of polyketide and nonribosomal peptide products can also be accurately predicted, given the well-understood logic of assembly line operations. Nonetheless, the identification of actual products is still lagging behind. The discovery of these bioactive molecules can be achieved, however, by establishing a unique connection between genomes and molecules. Using several concrete examples, this thesis demonstrates how both metabolomic and biochemoinformatic platforms can assist in discovery of bioactive small molecules. More specifically, investigations involving three members of the human microbiome, Streptococcus mutans, Lactobacillus plantarum and Pseudomonas aeruginosa, provide distinct examples of identification of bioactive agents and assessment of their immunomodulatory potential. Interrogating the human microbiome form the angle of small molecules is critical for evaluation of microbial effects on our cells, and ultimately our health. Studying these agents will hopefully reveal interesting principles on how microorganisms speak to human cells and how this communication could lead to therapeutic strategies or downstream mechanistic revelations. / Thesis / Master of Science (MSc) / The numerous benefits associated with natural products isolated from the environmental sources, including soil bacteria, plants and fungi, are long known and well appreciated. Interestingly, the immense number of microorganisms that reside within our bodies and whose cell counts greatly outnumber our own represents a potentially new and practically untapped reservoir of bioactive compounds. With the advent of next generation sequencing we are only now starting to realize the complexity and biological diversity of the human microbiome. With this ever-increasing flow of genomic information, more bioactive potential in these microbes can be identified. For instance, biosynthetic assembly lines responsible for the production of two largest classes of bioactive compounds, polyketides and nonribosomal peptides, can be readily identified within the microbial genomes, providing us with a view of their bioactive profiles. In addition to the identification of biosynthetic assembly lines, the building blocks of polyketide and nonribosomal peptide products can also be accurately predicted, given the well-understood logic of assembly line operations. Nonetheless, the identification of actual products is still lagging behind. The discovery of these bioactive molecules can be achieved, however, by establishing a unique connection between genomes and molecules. Using several concrete examples, this thesis demonstrates how both metabolomic and biochemoinformatic platforms can assist in discovery of bioactive small molecules. More specifically, investigations involving three members of the human microbiome, Streptococcus mutans, Lactobacillus plantarum and Pseudomonas aeruginosa, provide distinct examples of identification of bioactive agents and assessment of their immunomodulatory potential. Interrogating the human microbiome form the angle of small molecules is critical for evaluation of microbial effects on our cells, and ultimately our health. Studying these agents will hopefully reveal interesting principles on how microorganisms speak to human cells and how this communication could lead to therapeutic strategies or downstream mechanistic revelations.

Osteosarcoma (OS) is the most common primary bone tumor with an annual incidence rate of 3-4 individuals per million particularly affecting children and young adults. The 5-year survival rate stands at 60-80% with the current standard of care for human OS patients who do not have metastatic disease at presentation, but this drops to 20% for patients with metastatic disease which frequently occurs in the lungs. OS is much more common in canines, with metastasis being the major contributor to mortality, the same as in humans. Metastatic OS warrants novel treatment strategies to improve prognosis and survival. High-frequency irreversible electroporation (H-FIRE) is a promising, non-thermal, minimally invasive technique that induces cell death by applying pulsed electric fields in targeted regions, potentially triggering an anti-tumor immune response that could also target and prevent metastases. Such a dual functionality of H-FIRE is uniquely suited to treat pulmonary metastatic OS. The goal of this thesis was to study the ablative and immunomodulatory effects of H-FIRE on OS in-vitro with the overall hypothesis that H-FIRE completely ablates OS cells, induces the release of damage-associated molecular patterns (DAMPs), and promotes pro-inflammatory immune activating signatures in macrophages and T cells. Using an in-vitro model, my master's thesis focused on 1) Determining the electric field strength that completely ablates OS cells 2) Evaluating the immunomodulatory effects of H-FIRE by co-culturing H-FIRE treated OS cells with macrophages and T cells separately. Our study has utilized murine, canine, and human OS and immune cells, thus demonstrating a unique cross-species approach, 3) Evaluating DAMPs (ATP, calreticulin, and HMGB1) post-H-FIRE ablation of human OS cells. Overall, our study showed that H-FIRE successfully ablated OS cells in-vitro, induced the release of DAMPs from treated cells, and promoted activation signatures in immune cells. This thesis provides foundational data for future investigations developing H-FIRE as an immunomodulatory strategy for treating metastatic OS. / Master of Science / Osteosarcoma (OS) is the most common primary bone tumor that majorly affects young adults and children with an incidence rate of 3-4 individuals per million per year. When metastasis occurs (i.e. OS spreads from its site of origin to other organs in the body), most frequently to the lungs, patients experience poor chances of recovery and survival. Currently, the treatment protocol followed for patients with metastatic OS largely includes complete surgical removal and chemotherapy both of which can be very grueling for patients. No significant improvement in the overall 5-year survival rate with current mainstay treatment has led to the urgent need of novel treatment modalities for treating patients with pulmonary metastatic OS. High-Frequency Irreversible Electroporation (H-FIRE) is a novel non-thermal tumor ablation strategy that utilizes electrical pulses to create pores on the cell membrane, thus leading to irreversible damage and cell death. These dying tumor cells release certain molecules and proteins that send danger signals to activate the body's own immune system against the tumor. H-FIRE with its dual function of destroying the targeted tumor region via electroporation and distant metastases via activating immune system is uniquely suited to treat pulmonary metastatic OS. This thesis is the first to investigate H-FIRE ablation and immunomodulation for OS. We hypothesized that H-FIRE can completely destructs OS cells, promotes the release of danger signals, and causes immune activation. Using an in-vitro model, this thesis focused on 1) Determining the electric field strength needed for complete OS cell destruction by H-FIRE 2) Evaluating the immune activation potential of H-FIRE by exposing these H-FIRE treated cells to immune cells like macrophages and T cells separately. We utilized human, mouse, and dog-derived OS cells to increase the biological and clinical relevance of our study. 3) Evaluating certain proteins that act as danger signals post-H-FIRE treatment of human OS cells. Overall, our results indicated that H-FIRE can successfully destruct OS cells in-vitro, promotes the release of danger signals, and induces immune activation. This thesis contributes to providing crucial preliminary data in the development of H-FIRE as a novel ablation and immunomodulation treatment strategy for pulmonary metastatic OS.

Notre équipe a démontré précédemment que les cellules dendritiques (DC) traitées par l’Acide Mycophénolique (DC-MPA) induisaient des lymphocytes T (LT) CD4+ régulateurs (iTreg). Dans ce travail, nous avons démontré que les iTreg supprimaient l’allocytotoxicité des LT CD8+ indépendants des LT CD4+. D’autre part, nous avons montré que des LT préactivés en conditions inflammatoires induisaient via CTLA-4 la synthèse d’IL-12 par les DC. Le blocage de CD28 dans les mêmes conditions inhibait la production d’IL-10 et d’Interferon-g mais n’affectait pas celle d’IL-12. Enfin, des LT préactivés par des DC allogéniques différenciées en présence d’IL-10 (DC-10) étaient hyporéactifs, mais de façon surprenante, étaient dénués d’activité régulatrice. Ce travail a montré pour la première fois chez l’homme la capacité des Treg induits à réguler l’allocytotoxicité des LT CD8+. Il suggère aussi que CTLA-4 exprimée par des LT préactivés orientait la réponse immunitaire vers Th1, via un ligand sur la DC, non commun avec CD28. / This work has studied several aspects of the regulation of the immune response in human. Works in our laboratory have previously demonstrated that Mycophenolic Acid-Treated Dendritic Cells (MPA-DC) induced CD4+ regulatory T cells (iTreg). In this work and for the first time in human, we demonstrated that allospecific iTreg suppressed helpless CD8+ T-Cells allocytotoxicity. On the other hand, we have shown that preactivated T-Cells in inflammatory conditions induce IL-12 synthesis by DC through CTLA-4 engagement. Blockade of CD28 in this interaction inhibited the production of IL-10 and Interferon-g without affecting that of IL-12. Finally, allogeneic DC differentiated in the presence of IL-10 (DC-10) induced T cell hyporesponsiveness without any regulatory activity. This work has highlighted the ability of allospecific iTreg to regulate CD8+ T-Cells allocytotoxicity and suggested that the engagement of CTLA-4 expressed by preactivated T cells polarized the immune response towards Th1, via a ligand on DC, different from that of CD28.

Les cellules dendritiques (DCs) possèdent des rôles clés dans la modulation de la réponse inflammatoire. Leur implication dans la réponse inflammatoire post-ischémie/reperfusion semble claire. Cependant, leurs rôles spécifiques restent encore à élucider. Nous avons émis l’hypothèse selon laquelle la modulation de la réponse des cellules dendritiques suite à la séquence d’ischémie/reperfusion pourrait diminuer les lésions du greffon cardiaque. L’objectif de ce travail a donc consisté en l’exploration et l’identification d’un mécanisme immunomodulateur dans la DC. Un modèle cellulaire d’hypoxie/réoxygénation (H/R) et un modèle de co-culture DCs / cardiomyocytes ont été utilisés. / Dendritic cells (DCs) play key roles during the inflammatory process. Although their involvement in ischemia/reperfusion (I/R)-related inflammation is known, their specific role in such a context remain to be elucidated.We hypothesized that the modulation of DC phenotype during I/R might decrease cardiac graft injuries. In this study, we aimed to explore and identify an immunomodulatory mechanism in DCs. An in vitro model of hypoxia/reoxygenation (H/R) and a co-culture model were used. Our results highlight that the purinergic receptor P2Y11 (P2Y11R) exhibits an immunosuppressive role in DCs. This effect was lost when cells were subjected to a H/R insult, due to P2Y11R downregulation during hypoxia.

L’immunoglobuline A (IgA) est l’immunoglobuline la plus abondamment synthétisée chez les mammifères. Ses propriétés ambivalentes l’impliquent non seulement dans des fonctions de protection contre les agents pathogènes mais aussi dans des phénomènes de tolérance immunitaire vis-à-vis des germes commensaux du microbiote. Toutefois, les IgA peuvent développer des propriétés pathogènes. Dans la première partie de mon travail de thèse, nous avons étudié les effets pathogènes de l’IgA. Les dépôts d’IgA sur le mésangium sont la caractéristique de l’IgAN. La physiopathologie de cette maladie est mal connue. L’hypothèse d’un défaut de glycosylation de l’IgA est souvent retenue ; ce défaut peut être la cause de sa polymérisation et de son antigénicité, il peut aussi favoriser le clivage du récepteur CD89. Nous avons analysé l’effet du défaut d’affinité de la région variable des IgA, de la substitution de la chaîne légère ainsi que de l’association des IgA à leur récepteur, le CD89 sur l’induction des lésions et le dysfonctionnement rénal chez quatre modèles murins différents générés au laboratoire et suivis pendant 12 mois. Nous avons également étudié les propriétés physico-chimiques des IgA de 28 patients ayant une dysglobulinémie et de 28 IgA produites par des hybridomes ; la relation entre ces propriétés et la capacité des IgA à se déposer a été observée. Dans une seconde partie, nous avons étudié l’aspect immunomodulateur et les propriétés antiinflammatoires conférées par l’IgA humaine surexprimée chez un modèle murin de lupus systémique (souris MRL/lpr). Dans la dernière partie du travail, nous avons contribué à la caractérisation d’un modèle de souris transgénique exprimant l’IgA de classe 2 et à l’étude de l’effet de signalisation médiée par cette IgA2 sur le développement des populations lymphocytaires. L’ensemble de ces travaux a montré l’effet pathogène des IgA naturelles ayant une faible affinité sur le développement de la néphropathie à IgA ; ainsi les analyses des IgA des patients et des hybridomes montrent que c’est la stabilité moléculaire de préférence au profil de glycosylation qui joue un rôle crucial dans leur capacité de dépôt. L’expression des IgA humaines chez les souris lupiques a considérablement prolongé leur durée de vie et a ralenti la survenue de l’auto-immunité et de l’atteinte rénale ce qui témoigne du rôle anti-inflammatoire des IgA. L’étude du modèle murin exprimant l’IgA2 humaine a montré que la signalisation via l’IgA2 joue un rôle inhibiteur sur le développement précoce de certaines sous-populations de cellules B. L’ensemble de ces résultats montrent la multitude d’effets de l’IgA lui permettant d’intervenir d’une part dans la pathogenèse d’une maladie complexe (l’IgAN) et d’autre part dans la protection de l’auto-immunité, témoignant de la complexité des interactions mises en jeu et du caractère régulateur de cette immunoglobuline. / Immunoglobulin A (IgA) is the most synthetized immunoglobulin in mammals. IgA has ambivalent properties: it is implicated in the mechanisms of defense against pathogens but also in the immune tolerance of commensal microbiota. However, IgA can develop pathogenic properties. In the first part of my thesis, we studied the pathogenic effects of IgA. IgA deposits are the main characteristic of IgA nephropathy (IgAN). IgAN physiopathology is not yet clearly understood. The hypothesis of a glycosylation defect is strongly adapted. This defect can be due to IgA polymerization or antigenicity. It can also induce shedding of CD89 (IgA Fc receptor) or other factors. We studied the effect of variable region altered affinity, the light chain substitution and the association of IgA with CD89 on the development of kidney lesions and impairment of kidney function in four mouse models followed up during 12 months. In addition, we studied the physico-chemical properties of 28 IgA purified from patients with dysglobulinaemia and 28 chimeric IgA produced by hybridomas. The effect of these properties on the propensity of IgA for mesangial deposition was explored. In the second part, we studied the immunomodulatory and anti-inflammatory properties conferred by the overexpression of human IgA in a mouse model with systemic lupus (MRL/lpr model). In the last part, we contributed to the characterization of a transgenic mouse model producing IgA class 2 and to the study of the effect of IgA2-mediated signaling on B lymphocyte development. Altogether, obtained results show the pathogenic effect of low affinity-IgA on the development of IgA nephropathy. In addition, different analyses showed that molecular stability but not glycosylation profile is the determining factor for IgA deposition. On the other hand, IgA expression in lupus-prone mice extended their survival, delayed the onset of auto-immunity and ameliorated kidney functions in these animals which supports IgA anti-inflammatory properties. The study of IgA2-mediated signaling in the transgenic model showed the inhibitory effect of IgA2 on the early development of several B cell sub-populations. All of these results show the multiple effects of IgA which contribute on one hand to the pathogenesis of a complex disease (IgAN) and on the other hand to protection from autoimmunity, demonstrating the complexity of interactions and the regulatory character of this immunoglobulin.