Traffic of exosomes in vivo. (A) Six hours after intravenous injection, PKH67-labeled allogeneic exosomes (BALB/c) were captured by MOMA-1⁺ macrophages (panel A, detail in insert), ER-TR9⁺ macrophages (B) and CD11c⁺ DCs (C) of the splenic MZ. (D, E) PKH67 and donor MHC-I from internalized exosomes colocalized in the cytoplasm of splenic DCs (D) and were found within LAMP-1⁺ vesicles (E). Scale bar equals 5 μm. (F) CD11c⁺ DCs (red) with PKH67⁺ (green) inclusions (yellow due to overlap, arrows) close to the arteriole of the splenic follicle (asterisk, inset). (G) Internalization of PKH67-labeled exosomes by subsets of splenic DCs assessed by flow cytometry at different time points. Numbers indicate percentage of cells. (H) Capture of circulating PKH67⁺ exosomes by the liver. (I, J) PKH67-labeled exosomes were captured by hepatic F4/80⁺ Kupffer cells (I) and were not detected in CD11c⁺ DCs (arrows). Nuclei were stained with DAPI. × 200. Panels D, E, and inserts in A and F are magnified at × 1000. Data representative of 3 independent experiments.