Directly loaded LPS-matured exosomes are more potent in stimulating T-cell proliferation in vitro than indirectly loaded exosomes. (A) Exosomes derived from LPS, IFN-γ–matured, or immature BMDCs were directly loaded with OVA_323-339 peptide by acid elution or (B) indirectly loaded by pulsing BMDCs with OVA or BSA protein and cocultured in different concentrations with CFSE-labeled CD4⁺ T cells, sorted from the splenocytes of DO11.10 mice. Proliferation was detected 5 days later by flow cytometry, and results are expressed as the mean percentage plus or minus SEM of proliferating cells cultured in triplicate according to the dimming intensity of the CFSE-positive cells. One representative experiment of 3 is displayed. (C) Representative FACS plots from experiments shown in panels A and B (shown for 10 μg/mL).