DC review I

DC review I - Ariel Savina Sebastian Amigorena Phagocytosis...

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Ariel Savina Sebastian Amigorena Authors’ address Ariel Savina, Sebastian Amigorena Institut Curie, INSERM U653, Immunite ´ et Cancer, Paris, France. Correspondence to: Sebastian Amigorena Institut Curie INSERM U653 Immunite ´ et Cancer 26 rue d’Ulm 75248 Paris Cedex 05, France Tel.: 33 1 4234 6711 Fax: 33 1 4407 0785 E-mail: [email protected] Immunological Reviews 2007 Vol. 219: 143–156 Printed in Singapore. All rights reserved ª 2007 The Authors Journal compilation ª 2007 Blackwell Munksgaard Immunological Reviews 0105-2896 Phagocytosis and antigen presentation in dendritic cells Summary: Like macrophages and neutrophils, dendritic cells (DCs) are considered professional phagocytes. Even if the three cell types phagocytose parasites, bacteria, cell debris, or even intact cells very efficiently, the functional outcomes of the phagocytic event are quite different. Macrophages and neutrophils scavenge and destroy phagocy- tosed particles, a critical step in innate immunity. DCs, in contrast, have developed means to ‘preserve’ useful information from the ingested particles that serve to initiate adaptive immune responses. Thus, both phagosomal degradation and acidification are much lower in DCs than in macrophages or neutrophils. Reduced degradation results in the conser- vation of antigenic peptides and in their increased presentation on major histocompatibility complex class I and II molecules. In this article, we review the mechanisms that control this delicate equilibrium between phagosomal degradation/cytotoxicity and antigen presentation in the different families of phagocytes. Keywords: dendritic cells, antigen presentation, phagosomal pH, phagosomal degradation, cross-presentation Introduction Phagocytes represent a heterogeneous family of cells that includes neutrophils, macrophages, and dendritic cells (DCs). The first two cell types are critical effectors of innate immunity. They are both involved in the immediate clearance of pathogens through local inflammatory responses. DCs entered the exclusive club of phagocytes more recently. Unlike other phagocytes, DCs are not directly involved in immediate pathogen clearance. From this perspective, they cannot be considered ‘conventional’ effectors of innate immunity. Like macrophages, DCs are present in all peripheral tissues and accumulate at the sites of pathogen entry. DCs express a large array of phagocytic receptors and efficiently phagocytose pathogens. DCs also express a variety of Toll-like receptors (TLRs) and other pattern recognition receptors (PRRs). Various PRRs are selectively expressed in particular DC subpopulations, where they initiate different developmental programs (often 143
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referred to as ‘maturation’). During maturation, DCs produce cytokines and chemokines. They also undergo a series of phenotypic and functional modifications, depending on the type of PRRs they encounter (1). Contrary to other phagocytes, however, DCs are potent
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This note was uploaded on 01/03/2012 for the course BI 144 taught by Professor List during the Fall '10 term at Caltech.

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DC review I - Ariel Savina Sebastian Amigorena Phagocytosis...

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