ILVs

ILVs, or intraluminal vesicles, are membrane-bound vesicles formed inside multivesicular bodies (MVBs) of late endosomes. They arise by inward budding of the limiting membrane of the endosome and are contained within the lumen of the MVB. ILVs can be stored within cells or released into the extracellular space when the MVB fuses with the plasma membrane.

Formation of ILVs occurs mainly through two pathways. The best characterized is ESCRT-dependent budding, in which a series of protein complexes coordinate cargo selection, membrane bending, and vesicle scission. An ESCRT-independent route also exists, involving lipid-driven mechanisms such as ceramide formation and the activity of tetraspanin-enriched microdomains that influence cargo sorting and vesicle formation.

Most ILVs that are destined for release become exosomes, a class of small extracellular vesicles. Exosomes mediate intercellular communication by transferring a diverse cargo, including proteins, lipids, and nucleic acids, to recipient cells. The specific cargo reflects the cell type and physiological or pathological state and can influence immune responses, development, and disease progression.

In research and diagnostics, ILVs and exosomes are investigated for their roles in cancer, neurodegeneration, and immune regulation, as well as their potential as biomarkers or therapeutic vehicles. Analytical approaches to study ILVs include differential ultracentrifugation and density gradient separation, nanoparticle tracking analysis, electron microscopy, and profiling of surface and cargo proteins (for example, CD63, CD9, CD81, Alix, and TSG101).