Different mechanisms by which PDMVs may interact with target cells. PDMVs may (1) stimulate target cells directly via surface-expressed ligands acting as a kind of signaling complex (eg, CD154), (2) transfer surface receptors from one cell to another (eg, CD41, CXCR4), or (3) deliver proteins, mRNA, and bioactive lipids, and even serve as a vehicle (“Trojan horse” mechanism) to transfer infectious particles between cells (eg, prions).