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Review
, 163 (1), 26-32

Ectosomes as Modulators of Inflammation and Immunity

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Review

Ectosomes as Modulators of Inflammation and Immunity

S Sadallah et al. Clin Exp Immunol.

Abstract

Vesicles released by cells have been described using various names, including exosomes, microparticles, microvesicles and ectosomes. Here we propose to differentiate clearly between ectosomes and exosomes according to their formation and release. Whereas exosomes are formed in multi-vesicular bodies, ectosomes are vesicles budding directly from the cell surface. Depending upon the proteins expressed, exosomes activate or inhibit the immune system. One of the major properties of exosomes released by antigen-presenting cells is to induce antigen-specific T cell activation. Thus, they have been used for tumour immunotherapy. By contrast, the major characteristics of ectosomes released by various cells, including tumour cells, polymorphonuclear leucocytes and erythrocytes, are the expression of phosphatidylserine and to have anti-inflammatory/immunosuppressive activities similarly to apoptotic cells.

Figures

Fig. 1
Fig. 1
Exosomes and ectosomes are microvesicles budding from a membrane. (a) Exosomes are produced by inward budding into the late endosomal compartment, called multi-vesicular bodies (MVB). When MVB fuse with the cell membrane, exosomes are released as preformed vesicles. (b) Ectosomes are small membrane vesicles shed by many cells by budding directly from the cell membrane.
Fig. 2
Fig. 2
Confocal microscopy of erythrocyte ectosomes phagocytosed by human macrophages. Human monocyte-derived macrophages were incubated with fluorescently labelled ectosomes for 30 min, fixed and analysed by confocal laser microscopy. (a) Macrophages bind and ingest erythrocyte-derived ectosomes in absence of cytochalasin D (CytD). (b) Alternatively, macrophages were preincubated with CytD prior to the addition of labelled ectosomes showing absence of intracellular fluorescence. Phagocytosis of erythrocyte ectosomes was blocked.

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