Figure 1.

Formation of exosomes and microvesicles. Microvesicles (MVs) with irregular shapes are formed from the exocytosis of the plasma membrane and mainly contain cytoplasmic materials. By contrast, exosomes are formed from the endocytosis of the plasma membrane followed by the fusion of a multivesicular body and secondary exocytosis; the sizes of exosomes are smaller than those of MVs. The surface proteins of MVs mainly originate from the membranes of cells from which they are derived, and exosomes include CD63, CD81, and CD9.