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Blood Cells Mol Dis. 2005 Jul-Aug;35(1):17-20.

Direct stimulation of naïve T cells by antigen-presenting cell vesicles.

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Department of Immunology, IMM4, The Scripps Research Institute, 10550 N. Torrey Pines Road, La Jolla, CA 92037, USA.


T cells are activated through T cell receptor (TCR) recognition of peptidic fragments of antigen bound to major histocompatibility complex (MHC) molecules on antigen-presenting cells (APC). In addition, T cells require a costimulatory signal delivered through contact with other ligands on APC, especially B7 and ICAM-1 which bind to CD28 and LFA-1, respectively, on T cells. Under physiological conditions, T cell activation requires contact with viable APC. Under defined conditions, however, T cells can be activated by exosomes secreted by APC. Evidence will be presented that exosomes can be directly immunogenic for CD8(+) T cells in the absence of normal APC with the proviso that exosomes express a high density of MHC I/peptide complexes as well as B7 and ICAM-1. Similar findings apply to plasma membrane fragments prepared from APC sonicates.

[Indexed for MEDLINE]

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