biostudies-literatureAlawar NEuropean Research CouncilDeutsche Forschungsgemeinschafte70239https://www.ebi.ac.uk/biostudies/studies/S-EPMC12919372biostudies-literatureUnknown15(2)Small extracellular vesicles (sEVs) derived from cytotoxic T lymphocytes (CTLs) are emerging as potential mediators of antitumor immunity; however, their subcellular origins and functional properties remain incompletely defined. In this study, we investigated the intracellular routes and cytotoxic potential of CTL-derived exosomes. Using correlative light and electron microscopy, we discovered that CTL-derived exosomes originate from both classical multivesicular bodies (MVBs) and the recently identified multi core granules (MCGs). Through total internal reflection fluorescence microscopy, we demonstrated that, in contrast to MVB-derived exosomes, MCG-derived exosomes are released at the immunological synapse in a stimulus-dependent manner. To enable functional characterization, we developJournal of extracellular vesiclesT-Cell-Derived Exosomes From Multi Core Granules Exhibit Superior Caspase-3-Mediated Tumor-Suppressive Activity Compared to Those From Multivesicular Bodies.PMC12919372ERC-2021-SyG_951329ID number 469256325ID number 203827099SFB 894ID number 157660137Rettig JKeller ASchirra CDustin MLFecher-Trost CMeyer MRFlockerzi VRasuli RBecherer UAlawar NWeins LfalseT-Cell-Derived Exosomes From Multi Core Granules Exhibit Superior Caspase-3-Mediated Tumor-Suppressive Activity Compared to Those From Multivesicular Bodies.Small extracellular vesicles (sEVs) derived from cytotoxic T lymphocytes (CTLs) are emerging as potential mediators of antitumor immunity; however, their subcellular origins and functional properties remain incompletely defined. In this study, we investigated the intracellular routes and cytotoxic potential of CTL-derived exosomes. Using correlative light and electron microscopy, we discovered that CTL-derived exosomes originate from both classical multivesicular bodies (MVBs) and the recently identified multi core granules (MCGs). Through total internal reflection fluorescence microscopy, we demonstrated that, in contrast to MVB-derived exosomes, MCG-derived exosomes are released at the immunological synapse in a stimulus-dependent manner. To enable functional characterization, we develop2026-01-01T00:00:00Z2026 Feb2026-07-16T11:55:15.277Z2026-07-09T10:52:01.401ZS-EPMC129193724171163310.1002/jev2.70239