Lung surfactant protein D (SP-D) is a soluble pattern recognition and innate immune molecule, which has been shown to be protective against lung infection, allergy, asthma and inflammation. SP-D is composed of an N-terminal collagen region and a homotrimeric, C-terminal carbohydrate binding domain (CRD). A recombinant form of trimeric CRD region (rhSP-D) has been shown to offer protection against asthma and inflammation in murine models by bringing down IgE levels, eosinophilia, and causing T helper cell polarisation from a pathogenic Th2 to a protective Th1 phenotype. Thus, rhSP-D can provide a therapeutic effect by dampening asthmatic symptoms in mice. The therapeutic mechanisms include inhibition of allergen-IgE binding and histamine release by sensitized mast cells, downregulation of allergen/antigen-specific IgG and IgE antibodies, pulmonary and peripheral eosinophilia, a shift from Th2 to Th1 cytokine response, interference with airway remodelling processes, and apoptosis- induction in sensitised eosinophils from allergic patients. The majority of the ex vivo and in vivo studies where a therapeutic effect of rhSP-D has been reported can not be explained by hitherto described candidate receptor involvement, especially CD91-calreticulin complex that requires collagen region for its cellular response. Thus, it is pertinent to examine at the cellular and molecular level how a trimeric lectin domain of human SP-D modulates immune cells. This was achieved by firstly expressing, purifying and characterising the recombinant rhSP-D and examining the interaction of rhSP-D with various immune cells such as macrophages, which are potent antigen presenting cells and play a crucial role in the maintenance of the inflammatory and humoral response to allergens. The highlight of this study is the demonstration that rhSP-D interferes with the co-operative binding of allergen-IgE complexes to B cells, and also downregulates expression of CD23, a low affinity IgE receptor (FcεRII), found on B cells. This suggests that inhibition of IgE-facilitated antigen presentation may represent a mechanism whereby SP-D suppresses Th2-driven allergic inflammation. In addition, this study is also the first to establish the calcium-dependent interactions between rhSP-D, CD23 and CD21. The possibility of formation of a trimolecular complex on the B cell surface may account for the suppression of IgE in therapeutic murine models since rhSP-D may interfere with CD21-CD23 mediated IgE production by primed B cells.

Orientador: Carlos Rossa Junior / Banca: Alexandra Ivo de Medeiros / Banca: Luis Carlos Spolidorio / Banca: Ricardo Della Coletta / Banca: Roseanas Almeida Freitas / Resumo: Carcinoma espinocelular de cabeça e pescoço (HNSCC, squamous cell carcinoma of the head and neck) é uma neoplasia caracterizada mais comumente por invasão local/regional de prognóstico sombrio quando diagnosticada em estágios avançados e uma característica imunossupressão local ou sistêmica associada. A taxa de sobrevivência em casos avançados é inferior à de câncer de mama ou próstata, e seu tratamento usualmente causa morbidade severa. A resposta ao tratamento é altamente variável mesmo entre pacientes em estágios iniciais da doença e apesar do tratamento implementado seguir o padrão de cuidados vigente. Assim, há grande necessidade de identificar biomarcadores que indiquem um fenótipo agressivo e possa proporcionar informações de utilidade no desenvolvimento de novas terapias específicas. Nossa hipótese foi de que produtos secretados por células de HNSCC ou o contato direto das mesmas com células imunológicas podem induzir uma modulação no sentido de causar a evasão do tumor da resposta imune. Observamos que a literatura mostra diversos trabalhos onde células tumorais exercem efeito imunossupressor em diversos tipos celulares da resposta imune. O estímulo de PBMC com meio condicionado (CM) de células de HNSCC induziu uma diminuição na proliferação, bem como modulou a polarização para fenótipos anti-inflamatórios e em co-cultura de HNSCC e PBMC, o tratamento prévio com CM das PBMC conferiu vantagem às células tumorais. Por último avaliamos um possível biomarcador, a galanin... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Squamous cell carcinoma of head and neck (HNSCC) is a cancer characterized commonly by local/regional invasion of poor prognosis when diagnosed in advanced stages and are associated with local or systemic immunosuppression. The survival rate for advanced cases is below the breast or prostate cancer, and treatment usually causes severe morbidity. The response to the treatment is highly variable among patients even in the early stages of the disease, despite the treatment implemented following the current standard care. Thus, there is great need to identify biomarkers that indicate an aggressive phenotype and can provide useful information on the development of new target therapies. Our hypothesis was that secreted products by HNSCC cells or direct contact with immune cells can induce a modulation in order to cause tumor evasion of the immune response. We note that the literature shows several studies where tumor cells exert immunosuppressive effect in different cell types of the immune response. The stimulation of PBMC with conditioned medium (CM) of HNSCC cells induced a decrease in proliferation, and modulates a polarization toward anti-inflammatory phenotypes and in co-culture of HNSCC and PBMC pre-treatead with CM caused advantage to tumor cells. Finally we evaluate a possible biomarker, galanin, in modulating the immune response. The absence of galanin induced higher levels of proliferation as well a more bias towards proinflammatory phenotypes. Increase of galanin expres... (Complete abstract click electronic access below) / Doutor