Exosomes are saucer-shaped vesicles of 30–100 nm in diameter, which are delimited by a lipid bi-layer and which float at a density of 1.13–1.19 g ml−1 in sucrose gradients. These vesicles are secreted by various cells in culture.
Analysis of the protein composition of exosomes that are secreted by various cells reveals the presence of some common proteins, which define exosomes as a bona fide secreted subcellular compartment, as well as the presence of some cell-type-specific proteins, which could mediate the different functions of exosomes that are produced by different cell types.
All of the proteins that have been identified in exosomes are localized in the cell cytosol or endosomal compartments, never in the endoplasmic reticulum, Golgi apparatus, mitochondria or nucleus. Exosomes also contain some plasma-membrane proteins, which have been described also in endosomal compartments. These observations are consistent with the proposed origin of exosomes as internal vesicles of late multivesicular compartments.
Formation of the internal vesicles of multivesicular bodies by inward budding from the limiting membrane involves a budding event of inverse membrane orientation compared with the classical intracellular budding events that take place in a cell. All inverse budding events seem to be correlated with an inversion of the transmembrane partition of the lipid phosphatidylserine.
Membrane exchanges between cells have been described during the interactions of T cells and antigen-presenting cells (from the T cell to the antigen-presenting cell, or reciprocally, depending on the analyses), or between dendritic cells. It is not clear whether such exchanges involve exosomes.
The biological functions of exosomes remain unclear. The original role of exosomes was most probably to eliminate undegraded endosomal or lysosomal proteins and membranes. Recent results indicate, however, that in different cell types, exosomes might have other functions, such as the stimulation or inactivation of T cells, or the transfer of antigens to dendritic cells.
Regardless of their putative physiological functions, exosomes have been used successfully in preclinical mouse and human tumour immunotherapy assays. A Phase I clinical trial in melanoma patients is ongoing.
Exosomes are small membrane vesicles of endocytic origin that are secreted by most cells in culture. Interest in exosomes has intensified after their recent description in antigen-presenting cells and the observation that they can stimulate immune responses in vivo. In the past few years, several groups have reported the secretion of exosomes by various cell types, and have discussed their potential biological functions. Here, we describe the physical properties that define exosomes as a specific population of secreted vesicles, we summarize their biological effects, particularly on the immune system, and we discuss the potential roles that secreted vesicles could have as intercellular messengers.
Subscribe to Journal
Get full journal access for 1 year
only $22.08 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Trams, E. G., Lauter, C. J., Salem, N. Jr & Heine, U. Exfoliation of membrane ecto-enzymes in the form of micro-vesicles. Biochim. Biophys. Acta 645, 63–70 (1981).
Pan, B. T., Teng, K., Wu, C., Adam, M. & Johnstone, R. M. Electron microscopic evidence for externalization of the transferrin receptor in vesicular form in sheep reticulocytes. J. Cell Biol. 101, 942–948 (1985).
Harding, C., Heuser, J. & Stahl, P. Receptor-mediated endocytosis of transferrin and recycling of the transferrin receptor in rat reticulocytes. J. Cell Biol. 97, 329–339 (1983).References 2 and 3 describe very detailed and careful electron-microscopy analyses of the fate of an endocytosed protein in reticulocytes, and point out, for the first time, the possible secretion of the content of multivesicular late endosomes into the extracellular space.
Johnstone, R. M., Adam, M., Hammond, J. R., Orr, L. & Turbide, C. Vesicle formation during reticulocyte maturation. Association of plasma-membrane activities with released vesicles (exosomes). J. Biol. Chem. 262, 9412–9420 (1987).
Peters, P. J. et al. Molecules relevant for T-cell–target-cell interaction are present in cytolytic granules of human T lymphocytes. Eur. J. Immunol. 19, 1469–1475 (1989).
Raposo, G. et al. B lymphocytes secrete antigen-presenting vesicles. J. Exp. Med. 183, 1161–1172 (1996).This study shows, for the first time, the secretion of vesicles that are derived from multivesicular late endosomes by an antigen-presenting cell, and the presence of functional MHC class II molecules on the released exosomes.
Raposo, G. et al. Accumulation of major histocompatibility complex class II molecules in mast-cell secretory granules and their release upon degranulation. Mol. Biol. Cell 8, 2631–2645 (1997).
Zitvogel, L. et al. Eradication of established murine tumors using a novel cell-free vaccine: dendritic-cell-derived exosomes. Nature Med. 4, 594–600 (1998).This study shows that exosomes can be secreted by dendritic cells, and that such exosomes can induce antigen-dependent T-cell-mediated immune responses in mice.
Thery, C. et al. Molecular characterization of dendritic-cell-derived exosomes. Selective accumulation of the heat-shock protein hsc73. J. Cell Biol. 147, 599–610 (1999).
Heijnen, H. F., Schiel, A. E., Fijnheer, R., Geuze, H. J. & Sixma, J. J. Activated platelets release two types of membrane vesicles: microvesicles by surface shedding and exosomes derived from exocytosis of multivesicular bodies and α-granules. Blood 94, 3791–3799 (1999).
Davis, J. Q., Dansereau, D., Johnstone, R. M. & Bennett, V. Selective externalization of an ATP-binding protein structurally related to the clathrin-uncoating ATPase/heat-shock protein in vesicles containing terminal transferrin receptors during reticulocyte maturation. J. Biol. Chem. 261, 15368–15371 (1986).
Thery, C. et al. Proteomic analysis of dendritic-cell-derived exosomes: a secreted subcellular compartment distinct from apoptotic vesicles. J. Immunol. 166, 7309–7318 (2001).A detailed analysis, together with reference 9 , of the protein composition of dendritic-cell-derived exosomes, and a demonstration that they are distinct from apoptotic-cell-derived microvesicles.
Skokos, D. et al. Mast-cell-dependent B- and T-lymphocyte activation is mediated by the secretion of immunologically active exosomes. J. Immunol. 166, 868–876 (2001).
Martinez-Lorenzo, M. J. et al. Activated human T cells release bioactive Fas ligand and APO2 ligand in microvesicles. J. Immunol. 163, 1274–1281 (1999).
Blanchard, N. et al. TCR activation of human T cells induces the production of exosomes bearing the TCR/CD3/ζ complex. J. Immunol. 168, 3235–3241 (2002).
Wolfers, J. et al. Tumor-derived exosomes are a source of shared tumor rejection antigens for CTL cross-priming. Nature Med. 7, 297–303 (2001).
van Niel, G. et al. Intestinal epithelial cells secrete exosome-like vesicles. Gastroenterology 121, 337–349 (2001).
Nilsson, B. O., Lennartsson, L., Carlsson, L., Nilsson, S. & Ronquist, G. Expression of prostasome-like granules by the prostate cancer cell lines PC3, Du145 and LnCaP grown in monolayer. Ups. J. Med. Sci. 104, 199–206 (1999).
Hess, C., Sadallah, S., Hefti, A., Landmann, R. & Schifferli, J. A. Ectosomes released by human neutrophils are specialized functional units. J. Immunol. 163, 4564–4573 (1999).
Mack, M. et al. Transfer of the chemokine receptor CCR5 between cells by membrane-derived microparticles: a mechanism for cellular human immunodeficiency virus 1 infection. Nature Med. 6, 769–775 (2000).
MacKenzie, A. et al. Rapid secretion of interleukin-1β by microvesicle shedding. Immunity 15, 825–835 (2001).
Escola, J. M. et al. Selective enrichment of tetraspan proteins on the internal vesicles of multivesicular endosomes and on exosomes secreted by human B lymphocytes. J. Biol. Chem. 273, 20121–20127 (1998).
Rabesandratana, H., Toutant, J. P., Reggio, H. & Vidal, M. Decay-accelerating factor (CD55) and membrane inhibitor of reactive lysis (CD59) are released within exosomes during in vitro maturation of reticulocytes. Blood 91, 2573–2580 (1998).
Clayton, A. et al. Analysis of antigen-presenting-cell-derived exosomes, based on immuno-magnetic isolation and flow cytometry. J. Immunol. Methods 247, 163–174 (2001).
Srivastava, P. Interaction of heat-shock proteins with peptides and antigen-presenting cells: chaperoning of the innate and adaptive immune responses. Annu. Rev. Immunol. 20, 395–425 (2002).
Stubbs, J. D. et al. cDNA cloning of a mouse mammary epithelial cell surface protein reveals the existence of epidermal growth factor-like domains linked to factor VIII-like sequences. Proc. Natl Acad. Sci. USA 87, 8417–8421 (1990).
Denzer, K. et al. Follicular dendritic cells carry MHC class-II-expressing microvesicles at their surface. J. Immunol. 165, 1259–1265 (2000).The first direct observation of exosomes in a human tissue (tonsils) in the absence of any in vitro culture step. Most of the other data in this paper, however, are obtained after the in vitro culture of B cells.
Mobius, W. et al. Immunoelectron microscopic localization of cholesterol using biotinylated and non-cytolytic perfringolysin O. J. Histochem. Cytochem. 50, 43–55 (2002).
Gruenberg, J. & Maxfield, F. R. Membrane transport in the endocytic pathway. Curr. Opin. Cell Biol. 7, 552–563 (1995).
Babst, M., Odorizzi, G., Estepa, E. J. & Emr, S. D. Mammalian tumor susceptibility gene 101 (TSG101) and the yeast homologue, Vps23p, both function in late endosomal trafficking. Traffic 1, 248–258 (2000).
Vincent-Schneider, H. et al. Exosomes bearing HLA–DR1 molecules need dendritic cells to efficiently stimulate specific T cells. Int. Immunol. 14, 713–722 (2002).
Katzmann, D. J., Babst, M. & Emr, S. D. Ubiquitin-dependent sorting into the multivesicular body pathway requires the function of a conserved endosomal protein sorting complex, ESCRT-I. Cell 106, 145–155 (2001).
Hicke, L. A new ticket for entry into budding vesicles — ubiquitin. Cell 106, 527–530 (2001).
Reggiori, F. & Pelham, H. R. Sorting of proteins into multivesicular bodies: ubiquitin-dependent and -independent targeting. EMBO J. 20, 5176–5186 (2001).
Aupeix, K. et al. The significance of shed membrane particles during programmed cell death in vitro, and in vivo, in HIV-1 infection. J. Clin. Invest. 99, 1546–1554 (1997).
Mather, I. H. in The Mammary Gland (eds Neville, M. C. & Daniel, C. W.) 217–267 (Plenum, New York, 1987).
Peterson, J. A., Patton, S. & Hamosh, M. Glycoproteins of the human milk fat globule in the protection of the breast-fed infant against infections. Biol. Neonate 74, 143–162 (1998).
Garrus, J. E. et al. Tsg101 and the vacuolar protein sorting pathway are essential for HIV-1 budding. Cell 107, 55–65 (2001).
VerPlank, L. et al. Tsg101, a homologue of ubiquitin-conjugating (E2) enzymes, binds the L domain in HIV type 1 Pr55(Gag). Proc. Natl Acad. Sci. USA 98, 7724–7729 (2001).
Martin-Serrano, J., Zang, T. & Bieniasz, P. D. HIV-1 and Ebola virus encode small peptide motifs that recruit Tsg101 to sites of particle assembly to facilitate egress. Nature Med. 7, 1313–1319 (2001).
Blott, E. J. & Griffiths, G. M. Secretory lysosomes. Nature Rev. Mol. Cell Biol. 3, 122–131 (2002).
Pelham, H. R. SNAREs and the specificity of membrane fusion. Trends Cell Biol. 11, 99–101 (2001).
Paumet, F. et al. Soluble NSF attachment protein receptors (SNAREs) in RBL-2H3 mast cells: functional role of syntaxin 4 in exocytosis and identification of a vesicle-associated membrane protein-8-containing secretory compartment. J. Immunol. 164, 5850–5857 (2000).
Hibi, T., Hirashima, N. & Nakanishi, M. Rat basophilic leukemia cells express syntaxin-3 and VAMP-7 in granule membranes. Biochem. Biophys. Res. Commun. 271, 36–41 (2000).
Guo, Z., Turner, C. & Castle, D. Relocation of the t-SNARE SNAP-23 from lamellipodia-like cell-surface projections regulates compound exocytosis in mast cells. Cell 94, 537–548 (1998).
Martinez, I. et al. Synaptotagmin VII regulates Ca2+-dependent exocytosis of lysosomes in fibroblasts. J. Cell Biol. 148, 1141–1149 (2000).
Baram, D. et al. Synaptotagmin II negatively regulates Ca2+-triggered exocytosis of lysosomes in mast cells. J. Exp. Med. 189, 1649–1658 (1999).
Hwang, I. et al. T cells can use either T-cell receptor or CD28 receptors to absorb and internalize cell-surface molecules derived from antigen-presenting cells. J. Exp. Med. 191, 1137–1148 (2000).
Huang, J. F. et al. TCR-mediated internalization of peptide–MHC complexes acquired by T cells. Science 286, 952–954 (1999).
Hudrisier, D., Riond, J., Mazarguil, H., Gairin, J. E. & Joly, E. Cutting edge: CTLs rapidly capture membrane fragments from target cells in a TCR signaling-dependent manner. J. Immunol. 166, 3645–3649 (2001).
Stinchcombe, J. C., Bossi, G., Booth, S. & Griffiths, G. M. The immunological synapse of CTL contains a secretory domain and membrane bridges. Immunity 15, 751–761 (2001).
Brezinschek, R. I., Oppenheimer-Marks, N. & Lipsky, P. E. Activated T cells acquire endothelial cell-surface determinants during transendothelial migration. J. Immunol. 162, 1677–1684 (1999).
Russo, V. et al. Acquisition of intact allogeneic human leukocyte antigen molecules by human dendritic cells. Blood 95, 3473–3477 (2000).
Batista, F. D., Iber, D. & Neuberger, M. S. B cells acquire antigen from target cells after synapse formation. Nature 411, 489–494 (2001).
Patel, D. M., Arnold, P. Y., White, G. A., Nardella, J. P. & Mannie, M. D. Class II MHC/peptide complexes are released from APC and are acquired by T-cell responders during specific antigen recognition. J. Immunol. 163, 5201–5210 (1999).
Arnold, P. Y. & Mannie, M. D. Vesicles bearing MHC class II molecules mediate transfer of antigen from antigen-presenting cells to CD4+ T cells. Eur. J. Immunol. 29, 1363–1373 (1999).
Bedford, P., Garner, K. & Knight, S. C. MHC class II molecules transferred between allogeneic dendritic cells stimulate primary mixed leukocyte reactions. Int. Immunol. 11, 1739–1744 (1999).
Knight, S. C., Iqball, S., Roberts, M. S., Macatonia, S. & Bedford, P. A. Transfer of antigen between dendritic cells in the stimulation of primary T-cell proliferation. Eur. J. Immunol. 28, 1636–1644 (1998).
Sharrow, S. O., Mathieson, B. J. & Singer, A. Cell-surface appearance of unexpected host MHC determinants on thymocytes from radiation bone-marrow chimeras. J. Immunol. 126, 1327–1335 (1981).
Gray, D., Kosco, M. & Stockinger, B. Novel pathways of antigen presentation for the maintenance of memory. Int. Immunol. 3, 141–148 (1991).
Greco, V., Hannus, M. & Eaton, S. Argosomes: a potential vehicle for the spread of morphogens through epithelia. Cell 106, 633–645 (2001).This study shows a visualization in vivo in embryonic tissues of the transfer of membrane structures that are labelled with a fluorescent lipid between adjacent cells. The membrane structures that are involved have not been characterized.
Pan, B. T. & Johnstone, R. M. Fate of the transferrin receptor during maturation of sheep reticulocytes in vitro: selective externalization of the receptor. Cell 33, 967–978 (1983).
Karlsson, M. et al. 'Tolerosomes' are produced by intestinal epithelial cells. Eur. J. Immunol. 31, 2892–2900 (2001).
Dukers, D. F. et al. Direct immunosuppressive effects of EBV-encoded latent membrane protein 1. J. Immunol. 165, 663–670 (2000).
Monleon, I. et al. Differential secretion of Fas ligand- or APO2 ligand/TNF-related apoptosis-inducing ligand-carrying microvesicles during activation-induced death of human T cells. J. Immunol. 167, 6736–6744 (2001).
Andreola, G. et al. Induction of lymphocyte apoptosis by tumor-cell secretion of FasL-bearing microvesicles. J. Exp. Med. 195, 1303–1316 (2002).
André, F. et al. Malignant ascitis accumulate immunogenic tumor-derived exosomes: novel approach for cancer immunotherapy. Lancet (in the press).
Kleijmeer, M. J. et al. Antigen loading of MHC class I molecules in the endocytic tract. Traffic 2, 124–137 (2001).
Rieu, S., Geminard, C., Rabesandratana, H., Sainte-Marie, J. & Vidal, M. Exosomes released during reticulocyte maturation bind to fibronectin via integrin α4β1. Eur. J. Biochem. 267, 583–590 (2000).
We thank C. Hivroz and P. Benaroch for helpful comments on the manuscript. S.A. and L.Z. were supported by European Community grants.
A family of cytosolic proteins that have phospholipid-binding domains, the association of which with intracellular membranes is regulated by Ca2+. Several annexins are involved in membrane-fusion events between intracellular compartments.
- RAB PROTEINS
Cytosolic proteins that have GTPase activity, which, in their GTP-bound form, associate with membranes. Different RAB proteins associate with different intracellular compartments — for example, RAB5 associates with early endosomes, RAB7 with late endosomes and RAB11 with recycling endosomes.
- HEAT-SHOCK PROTEINS
(HSPs). A family of proteins that are involved in the binding of other misfolded proteins, and transporting them to the cellular degradation machinery. Several HSPs are synthesized only in conditions of stress, such as heat shock, but a few family members — such as endoplasmic-reticulum-resident gp96, and cytosolic HSC70 and HSP84 — are expressed constitutively.
A family of transmembrane proteins that have four transmembrane domains and two extracellular domains of different sizes, which are defined by several conserved amino acids in the transmembrane domains. Their function is not known clearly, but they seem to interact with many other transmembrane proteins and to form large multimeric protein networks.
In mastocytes and cytotoxic T lymphocytes, this term refers to the activation-induced fusion of secretory granules with the plasma membrane, and to the subsequent release of the content of these granules into the extracellular space.
- FOLLICULAR DENDRITIC CELLS
(FDCs). Cells with a dendritic morphology that are present in the lymph nodes, where they present intact antigens held in immune complexes to B cells. FDCs are of non-haematopoietic origin, and are not related to dendritic cells.
This term refers to the ability of certain antigen-presenting cells (APCs) to load peptides that are derived from exogenous antigens onto MHC class I molecules. This property is atypical, as most cells present exclusively peptides from their endogenous proteins on MHC class I molecules. Cross-presentation is essential for the initiation of immune responses against viruses that do not infect APCs.
About this article
Cite this article
Théry, C., Zitvogel, L. & Amigorena, S. Exosomes: composition, biogenesis and function. Nat Rev Immunol 2, 569–579 (2002). https://doi.org/10.1038/nri855
Signal transducer and activator of transcription 3 in myeloid-derived suppressor cells: an opportunity for cancer therapy
Altered Biogenesis and MicroRNA Content of Hippocampal Exosomes Following Experimental Status Epilepticus
Frontiers in Neuroscience (2020)
Tumor‐Exocytosed Exosome/Aggregation‐Induced Emission Luminogen Hybrid Nanovesicles Facilitate Efficient Tumor Penetration and Photodynamic Therapy
Angewandte Chemie (2020)
Journal of Extracellular Vesicles (2020)
Polymer-Based Precipitation of Extracellular Vesicular miRNAs from Serum Improve Gastric Cancer miRNA Biomarker Performance
The Journal of Molecular Diagnostics (2020)