Role of dendritic cells in innate immunity. Genome-wide profiling of DC in response to pathogens Principal Investigator:
Paola Ricciardi-Castagnoli
Coworkers:
Andrea Splendiani, Norman Pavelka, Mattia Pellizzola, Ottavio Beretta, Maria Foti
Keywords:
Immunity, Dendritic cells, Functional genomics; Microarray, Bioinformatics;
Project Description
Complex interactions regulate living organism functions. Understanding how the constituents of a biological system interact each others, is as important as understanding their function in a reductionistic experimental model, which does not take into account the biological complexity. Microarray technology is used in our laboratory to identify genes involved in the regulation of many processes regarding the immune system. In particular we are interested to investigate the response of dendritic cells to pathogens.
Dendritic cells (DCs) are sentinels of the immune system. In their immature state, DC are mainly distributed in tissues where they survey incoming pathogens. Any encounter with microbial products initiates the migration of DCs to the lymph nodes where they interact with antigen-specific CD4 or CD8 T cells to initiate acquired immune responses. Key functions of DCs include uptake and processing of antigen and priming of naïve T cells, functions that are segregated in time. Immature resting DCs located in nonlymphoid tissues, such as skin and mucosae, take up antigen. Mature DCs loaded with antigen and capable of priming T cells migrate from nonlymphoid tissues to the T cell area of lymph nodes or spleen. Thus, when immature DCs come into contact with infectious agents, they undergo a maturation process that transforms them from phagocytic and migratory cells to nonphagocytic, highly efficient stimulators of naïve T cell responses. The plasticity of DCs can be reproduced in vitro. Immature monocyte-derived human DCs (hMDCs) or immature bone marrow–derived mouse DCs (mBMDCs) can be induced to mature in vitro with many different stimuli including live microorganisms that represent the most potent catalysts of the DC terminal differentiation process as they induce a rapid and effective DC phenotypic and functional maturation. A key part of the complexity of innate and acquired immunity to microorganisms relies on how they affect DC activation.
In order to study how DCs are conditioned by microbial encounter, we carried out a kinetic analysis of gene expression in immature mouse DCs stimulated at different time-points with live bacteria (such as E.Coli), live helminth (such as Shistosoma eggs) and live parasites (such as Leishmania mexicana).A comparative analysis of the various transcriptomes generated has been obtained. Many genes, which were differentially expressed during maturation, encoded transcription factors, signal transduction molecules and proteins involved in cytoskeletal rearrangements or in the activation and control of immune responses.
The function of these new candidates, identified by comparative analysis, will be validated in vitro using iRNA technology and a series of bio-assays that will measure DC biological responses.
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