What are the classifications of extracellular vehicles (Evs)?

EVs are classified based on size, formation, and release mechanism. 

Exosomes

Exosomes, also known as small EVs, range from 50 to150 nm in diameter. They are the smallest of the three types of extracellular vesicles. 

They are formed intracellularly by inward budding of the endosomal membrane and secreted via exocytosis from the late endosome multivesicular bodies or MVBs. When MVBs fuse with the plasma membrane, they release intraluminal vesicles (ILVs) as exosomes.

Exosomes carry proteins, nucleic acids, and lipids, and are involved in cell-to-cell communication. They are conserved across various cell types.

Microvesicles (MVs)

Micovesicles or medium EVs, range in diameter from 100 to1000 nm.

They are formed directly by outward budding of the plasma membrane.  

Like exosomes, microvesicles also carry bioactive molecules and are involved in cell-to-cell communication.

Apoptotic Bodies

Apoptotic bodies, also known as large EVs, range from 800 to 5000 nm in diameter. They are the largest of the three types of extracellular vesicles.

They are produced when cells undergo apoptosis (programmed cell death), leading to the fragmentation of the cell into smaller vesicles.

Though once thought to be mere cellular debris, apoptotic bodies are now recognized for their ability to deliver useful materials to healthy cells and serve as biomarkers.

Overlapping characteristics can make it challenging to clearly differentiate the three classes of EVs.