Figure 2

Immuno-magnetic isolation of exosomes secreted by EBV-positive NPC cells expressing LMP1 (C15) or not (C17). Upper panel: electron-microscopy examination of magnetic beads following incubation with low density vesicles derived from C15 and C17 cell culture supernatant (× 90,000). The beads have a 4.5 μm diameter. Numerous vesicules of about 70 nm in diameter are bound to magnetic beads coated with anti-HLA II antibodies. In contrast Ig-coated beads did not yield any bound exosomes. Insert : One exosome at high magnification with a typical 7–8 nm lipid bilayer (× 135,000). Lower panel: Western blot analysis of bead-bound proteins. LMP1 is contained in C15 but not C17 exosomes whereas galectin 9 is contained in exosomes from both tumor lines, although less abundant in C17 exosomes. In addition to exosome material, light Ig chains are released from control beads as well as HLA class II beads confirming that both types of beads have been subjected to the same conditions of elution (in contrast heavy chains covalently bound to the beads are not released by boiling in gel loading buffer).