Journal of Cell Science 113, 3365-3374 (2000) 3365
Printed in Great Britain © The Company of Biologists Limited 2000
JCS1498
COMMENTARY
Exosome: from internal vesicle of the multivesicular body to intercellular signaling device
Kristin Denzer, Monique J. Kleijmeer, Harry F. G. Heijnen, Willem Stoorvogel and Hans J. Geuze*
Department of Cell Biology, Institute of Biomembranes and Centre for Biomedical Genetics, University Medical Center Utrecht, The Netherlands
*Author for correspondence (e-mail: h.j.geuze@lab.azu.nl)
Published on WWW 13 September 2000
Summary
Exosomes are small membrane vesicles that are secreted by a multitude of cell types as a consequence of fusion of multivesicular late endosomes/lysosomes with the plasma membrane. Depending on their origin, exosomes can play roles in different physiological processes. Maturing reticulocytes externalize obsolete membrane proteins such as the transferrin receptor by means of exosomes, whereas activated platelets release exosomes whose function is not yet known. Exosomes are also secreted by cytotoxic T cells, and these might ensure specific and efficient targeting of cytolytic substances to target cells. Antigen presenting cells, such as B lymphocytes and dendritic cells, secrete MHC class-I- and class-II-carrying exosomes that stimulate T cell proliferation in vitro. In addition, dendritic-cell-derived exosomes, when used as a cell-free vaccine, can eradicate established murine tumors. Although the precise physiological target(s) and functions of exosomes remain largely to be resolved, follicular dendritic cells (accessory cells in the germinal centers of secondary lymphoid organs) have recently been shown to bind B-lymphocyte-derived exosomes at their cell surface, which supports the notion that exosomes play an immunoregulatory role. Finally, since exosomes are derived from multivesicular bodies, their molecular composition might provide clues to the mechanism of protein and lipid sorting in endosomes.
Key words: Exosome, Multivesicular body, Sorting, Antigenpresentation
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