Mechanisms of FcεRI-IgE-Facilitated Allergen Presentation by Dendritic Cells
Dendritic cells (DC) are of key importance for the induction of antigen-specific T cell immunity. In their immature state, DC capture antigen at peripheral sites and, thereafter, migrate to secondary lymphoid organs where they, as matured cells, efficiently present antigen-derived peptides to naive T cells (1). It is obvious that the antigen recognition, capture and internalization functions of immature DC are of major biological relevance as they are the prerequisite for the occurrence, quantity and, perhaps, quality of antigen-specific T cell responses. For a long period, it was generally believed that antigen uptake by DC is mainly accomplished by micropinocytosis. In addition to this non-selective process, three other antigen uptake mechanisms of DC were recently discovered (2). The first is macropinocytosis, an actin-dependent type of fluid phase endocytosis that is mediated by membrane ruffling and characterized by the appearance of large cytoplasmic vesicles in which macrosolutes become concentrated (3). The two other uptake mechanisms are antigen/IgG complex- or glycosylation pattern-specific and rely on the presence of cell surface receptors. DC express FcγRII- and the mannose receptor that enable efficient capture of IgG complexed antigens (4, 5) and mannosylated/fucosylated antigens (3, 6), respectively. In rodents, DC express a further C-type lectin receptor, DEC-205, which recognizes specific glycosylation patterns on proteins and, thus, may be involved in the selective uptake and presentation of certain pathogens (7).
KeywordsDendritic Cell Mannose Receptor Immature Dendritic Cell Antigen Uptake Fluid Phase Endocytosis
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