Figure 1. Sequential steps necessary for exosome-mediated communication. Intralumenal vesicles (ILV) are formed after the invagination of the multivesicular endosome membrane. These ILVs are loaded with specific cargo originated from the plasma membrane and/ or the cytoplasm (A). Notice that the internal face of an ILV membrane corresponds to the cytoplasmic face of the endosome limiting membrane, and the ILV is loaded with cytosolic components. Upon fusion of the MVE with the plasma membrane (B), ILV are secreted as exosomes (C). Exosomes can be lost (D) or taken up by target cells (E) by fusion, or internalization mediated by surface molecules or by macropinocytosis. Additional abbreviation: ESCRT, endosomal sorting complex required for transport.