(A) Western blot analysis of PD-L1 expression in exosomes (top panel) and membrane extractions (detergent phase). Exosome markers (Tsg101 and Alix) were blotted as loading controls. (B) Flow cytometry analysis of isolated exosomes (in brown box) labeled with a violet dye (PB450 channel) and sizing beads (0.03–2.0 µm) labeled with a green dye (FITC channel). (C) Western blot analysis of the binding assay of exosomes with purified PN-1 [43]. The wildtype prostasin in exosomes is active and able to form a covalent bound with its cognitive inhibitor PN-1 shifting the molecular weight of prostasin from 35 kDa (prostasin alone) to 75 kDa (prostasin and PN-1 complex). HSP70 and CD63 were blotted as loading controls for exosomes.