Fig. 1

Biogenesis, characterization, and uptake of vesicle subtypes. The early endosomal membrane is depressed to form intraluminal vesicles, which aggregate to generate intracellular multivesicular bodies (MVBs). In turn, the MVBs isolate specific proteins, lipids, and other components in the cytoplasm and then generate exosomes (50–150 nm) via fusion with the plasma membrane or transport lysosomes for degradation. The released exosomes can enter the recipient cells via three routes: ligand–receptor binding on the receptor cell surface, endocytosis, and membrane fusion. Other types of vesicles include microvesicles and apoptotic bodies. Microvesicles (100–1000 nm) are released directly from living cells; they bud from the plasma membrane, are released into the extracellular environment after cell activation, and enter recipient cells through vesicle fusion or endocytosis. Meanwhile, apoptotic bodies (> 1000 nm) are released from dead cells without direct fusion to the plasma membrane