Previously believed to be no more than garbage disposal systems of the cell, evidence is rapidly accumulating to the role of exosomes as messengers conveying information between cells. As small membrane vesicles released by endocytosis, exosomes carry proteins, lipids, miRNA and mRNA specific to the type of cell from which they originate, be it T cells, B cells, dendritic cells, platelets, neurons, or epithelial cells. They transport this payload as they travel in biological fluids to distant tissues.
Due to their small size (≤150 nm), capturing and examining exosomes has proven challenging. Detection of single exosomes is very difficult via flow cytometry, but it is possible to gain insights about a population of exosomes. Proteins on the surface of exosomes can be stained with fluorochrome-conjugated antibodies to characterize populations originating from a particular cell type.