Tumor-derived exosomes are a source of shared tumor rejection antigens forCTL cross-priming

The initiation of T-cell-mediated antitumor immune responses requires the u ptake and processing of tumor antigens by dendritic cells and their present ation on MHC-I molecules. Here we show in a human in vitro model system tha t exosomes, a population of small membrane vesicles secreted by living tumo r cells, contain and transfer tumor antigens to dendritic cells. After mous e tumor exosome uptake, dendritic cells induce potent CD8(+) T-cell-depende nt antitumor effects on syngeneic and allogeneic established mouse tumors. Therefore, exosomes represent a novel source of tumor-rejection antigens fo r T-cell cross priming, relevant for immunointerventions.