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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Identificação de peptídeos de Escherichia coli capazes de inibir a própria fagocitose em sepse / Identification of Escherichia coli peptides that can inhibit its own phagocytosis in sepsis

Jaqueline Beppler 22 May 2015 (has links)
Introdução: Sepse é uma síndrome complexa definida por resposta inflamatória sistêmica, de origem infecciosa e caracterizada por manifestações múltiplas que podem determinar disfunção ou falência de um ou mais órgãos ou sistemas. É a principal causa de morte em unidades de terapia intensiva em pacientes críticos e tem representado uma fonte constante de preocupação para os sistemas de saúde em todo o mundo, devido, principalmente, às taxas elevadas de morbimortalidade. O tratamento da sepse é um desafio e continua a ser uma tarefa difícil devido a inúmeros fatores interferentes. Um estudo do nosso grupo demonstrou que a Escherichia coli (E. coli) é capaz de se ligar CD16 de um modo independente de opsonina, levando a um aumento na resposta inflamatória e a inibição da sua própria fagocitose, por conseguinte, procurou-se identificar os peptídeos no proteoma da E. coli envolvidos neste cenário. Metodologia: Utilizando a metodologia de Phage Display, que consiste numa técnica de clonagem, que permite a expressão de diversas sequências de peptídeos na superfície de bacteriófagos, nós identificamos 2 peptídeos que obtiveram interação com CD16. Após a seleção dos peptídeos identificamos uma proteína de membrana de E.coli que possui alta similaridade com um de nossos peptídeos selecionados. Nós acreditamos que esta proteína de membrana possa estar envolvida no processo de evasão imune desenvolvida pela E.coli e parece ser um forte candidato como uma nova opção terapêutica para controlar infecções por E. coli. Conclusão: A identificação de proteínas capazes de induzir inibição de fagocitose, através do receptor CD16, pode ser usada como uma nova forma de tratamento da sepse, assim como explorada no tratamento de doenças autoimunes / Introduction: Sepsis is a complex syndrome defined by a systemic inflammatory response of infectious origin and characterized by multiple manifestations that can determine dysfunction/failure of one or more organs and systems. It is the leading cause of death in intensive care units and represents a major health problem around the world, mainly due to its high mortality and morbidity rates. The treatment of sepsis is challenging and remains a difficult task due to numerous interfering factors. A study from our group demonstrated that Escherichia coli (E. coli) is able to bind CD16 in an opsoninindependent manner, leading to an increase in the inflammatory response and inhibition of its own phagocytosis, therefore we sought to identify the peptides in the E. coli proteome involved in this scenario. Methods and Results: Using the Phage Display technique, which is a cloning technique that allows the expression of various peptide sequences on the surface of bacteriophages (phages) and selecting these on the basis of affinity for a target molecule, we identified two peptides that interact with CD16. Next, using bioinformatic tools, we found an E. coli membrane protein that has high similarity with one of our selected peptides. We believe this membrane protein is involved in the process of immune evasion developed by E. coli and it is a strong candidate as a new therapeutic option to control E. coli infections. Conclusion: The identification of proteins capable of inducing inhibition of phagocytosis through the CD16 receptor, can be used as a new treatment of sepsis, as well as exploited in the treatment of autoimmune diseases
42

Feedback Enhancement of Antibody Responses via Complement and Fc Receptors

Dahlström, Jörgen January 2001 (has links)
<p>IgG, IgM and IgE in complex with antigen have the capacity to regulate specific immune responses. In this investigation, the role of Fc receptors for IgG (FcγRI, FcγRII and FcγRIII) and complement receptors 1 and 2 (CR1/2) for antibody-mediated enhancement of antibody responses are investigated.</p><p>IgM is known to efficiently activate complement and thereby enhance specific antibody responses but it is not known if this involves binding to CR1/2. Using CR1/2 deficient mice, immunized with sheep erythrocytes alone or together with specific IgM, we present evidence that IgM-mediated enhancement is completely dependent on CR1/2 expression, whereas IgG or IgE in complex with bovine serum albumin (BSA) induce strong antibody responses in CR1/2-deficient mice. Enhancement by IgE is mediated via the low affinity receptor for IgE (FcεRII, CD23). However, the receptors which are involved in IgG-mediated enhancement are not known. We find that γ-chain-deficient mice (lacking FcγRI and FcγRIII) have impaired antibody responses to IgG/BSA complexes. In contrast, FcγRIII deficient mice have normal responses, suggesting that FcγRI mediates the effect. Furthermore, IgG/BSA complexes induce up to 189-fold stronger antibody responses in FcγRIIB-deficient mice than in wild-type mice. The threshold dose of IgG/BSA required was lower, the response was sustained for longer and initiated earlier in FcγRIIB-deficient than in wild-type animals. The findings suggest that FcγRIIB acts as a "safety-valve" preventing excessive antibody production during an immune response. We show for the first time that IgG3/BSA complexes can mediate enhancement of specific antibody responses. Their effect does not involve known Fcγ receptors.</p>
43

Feedback Enhancement of Antibody Responses via Complement and Fc Receptors

Dahlström, Jörgen January 2001 (has links)
IgG, IgM and IgE in complex with antigen have the capacity to regulate specific immune responses. In this investigation, the role of Fc receptors for IgG (FcγRI, FcγRII and FcγRIII) and complement receptors 1 and 2 (CR1/2) for antibody-mediated enhancement of antibody responses are investigated. IgM is known to efficiently activate complement and thereby enhance specific antibody responses but it is not known if this involves binding to CR1/2. Using CR1/2 deficient mice, immunized with sheep erythrocytes alone or together with specific IgM, we present evidence that IgM-mediated enhancement is completely dependent on CR1/2 expression, whereas IgG or IgE in complex with bovine serum albumin (BSA) induce strong antibody responses in CR1/2-deficient mice. Enhancement by IgE is mediated via the low affinity receptor for IgE (FcεRII, CD23). However, the receptors which are involved in IgG-mediated enhancement are not known. We find that γ-chain-deficient mice (lacking FcγRI and FcγRIII) have impaired antibody responses to IgG/BSA complexes. In contrast, FcγRIII deficient mice have normal responses, suggesting that FcγRI mediates the effect. Furthermore, IgG/BSA complexes induce up to 189-fold stronger antibody responses in FcγRIIB-deficient mice than in wild-type mice. The threshold dose of IgG/BSA required was lower, the response was sustained for longer and initiated earlier in FcγRIIB-deficient than in wild-type animals. The findings suggest that FcγRIIB acts as a "safety-valve" preventing excessive antibody production during an immune response. We show for the first time that IgG3/BSA complexes can mediate enhancement of specific antibody responses. Their effect does not involve known Fcγ receptors.

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