Stress enhances the immunosuppressive effect of NKG2DL-bearing exosomes.

<p>NK-cell cytotoxicity assay using PBMC from healthy donors and K562 targets at an E∶T ratio 40∶1. The cytotoxic effect was measured in the presence or absence of exosomes released from cells cultured under steady state or stressed conditions. The cytotoxic response of untreated or antibody-blocked effector and target cells are shown in blue staples. The suppression of cytotoxicity by native exosomes released from cells cultured in various conditions is shown in red staples. Gray staples underlayed under the red staples show reversal of cytotoxicity to normal levels when the exosomes were blocked with a cocktail of Abs against NKG2DL or with Abs against the exosomal marker CD63. Green staple shows the level of cytotoxicity in the presence of used supernatant after exosome isolation indicating that the suppressive effect was associated with the exosomal fraction. * and ^# indicates statistical significance, p<0.05.