Figure 1.

Biogenesis, secretion, uptake and the schematic presentation of exosomes. Endosomes are formed by the inward budding of the cell membrane. Multivesicular bodies (MVBs) originate in the lumen of the endosomes by an inward budding of the endosomal membrane, which has two outcomes: either fusing with the plasma membrane to release its intraluminal vesicles to the extracellular space (called exosomes) or fusing with lysosomes for lysosomal degradation. The three types of mechanisms of exosome uptake by recipient cells are fusion, binding, and endocytosis. In general, the exosomes are formed with the following molecules: tetraspanin family (CD9, CD63, and CD81), lipid rafts, integrin, tumor susceptibility gene 101 (TSG101), major histocompatibility complex (MHC) class II molecules, heat shock proteins (HSP60, HSP70, and HSP90), annexins, and nucleic acids.