Flow cytometry analysis of B7H6 expression on tumor cells were performed by staining cells with anti-B7H6 mAbs,8 (link) followed by DyLight 649-conjugated goat anti-mouse IgG (clone: Poly4053, Biolegend, San Diego, CA). For staining of mouse cells, the samples were pre-incubated with FcR block antibody (anti-mouse CD16/CD32, 2.4G2; Bio X Cell, Lebanon, NH), and for staining of human cells, samples were pre-incubated with human gamma globulin (Cohn fraction, Sigma-Aldrich). Samples were analyzed by Accuri C6 cytometer (BD Biosciences, San Jose, CA) and data was analyzed by Accuri or FlowJo software (TreeStar Inc, Ashland, OR).