Dendritic cell-derived exosomes in cancer immunotherapy: exploiting nature's antigen delivery pathway.

Dendritic cells release large quantities of exosomes, known as dexosomes. These dexosomes are heat-stable, small vesicles (60–90 nm in diameter) made up of a lipid bilayer displaying an enrichment in sphingomyelin and a decrease in phosphatidylcholine content with no measurable asymmetry. They incorporate a characteristic set of proteins, including a large quantity of tetraspanins such as CD9 and CD81, all the known antigen presenting molecules (major histocompatibility complex class I and II, CD1 a, b, c and d) and the costimulatory molecule CD86. The function of dexosomes is to transfer - antigen-loaded major histocompatibility complex class I and II molecules, and other associated molecules, to naive dendritic cells, potentially leading to the amplification of the cellular immune response. In preclinical mouse models, antigen-loaded dexosomes elicit strong antitumor activity. Human dexosomes can be prepared ex vivo relatively easily from dendritic cells derived from monocytes isolated by leukapheresis ...