Enhanced cytotoxic responses to exosomal-protein in CD169^−/−mice. C57BL/6 or CD169^−/− mice were immunized (A) IV or (B) SC with PBS, pellet from exosome sucrose cushion purification (IV: B6 Sucr. Pellet), 50 μg sucrose cushion purified Exo-pro or 100 µg Exo-pro (purified by ultracentrifugation), 10⁵ DC-pro, or 10⁵ parental B cell-pro. Seven days after immunization, mice were adoptively transferred with unpulsed (CFSE low) or OVA_257-264-pulsed (CFSE high) target cells. In vivo killing was analyzed 18 hours later by flow cytometry. Results representative of ≥6 mice per group. One-way ANOVA with Bonferroni postcorrection was performed: *P < .05; ****P < .0001.