Fig. 4

The exosomes from ER-stressed OSCC cells upregulate macrophage PD-L1 expression and induce macrophage polarization toward the M2 subtype in vitro. A TEM image of the exosomes isolated from IFN-γ-stimulated (ER-stressed model) HN4 cells (Exo-ER) (scale = 200 nm). B Equal amounts of proteins from the exosomes secreted by IFN-γ-stimulated (Exo-ER) or untreated HN4 cells (Exo-Con) were analyzed using western blotting for exosome-enriched protein CD63, TSG101, and CD81. C Zeta potential measurements for the Exo-ER. D PD-L1 protein levels in Exo-ER and Exo-Con. E Quantification of the PD-L1 protein levels in panel (D). F PKH26-labeled Exo-ER were incubated with THP-1 macrophages and examined using confocal microscopy (scale bar = 50 μm), and the representative images are shown. G–I The PD-L1 mRNA and protein levels were detected using qRT-PCR (G) and western blot (H and I) analyses in THP-1 macrophages incubated with Exo-ER and Exo-Con. J The M2 macrophage markers were detected using qRT-PCR in the THP-1 macrophages incubated with Exo-ER and Exo-Con (n = 2–3) (*P < 0.05, **P < 0.01, and ***P < 0.001)