Cd28h

Redirected cytotoxicity assays were performed as described(4 (link)). Briefly, P815 cells were incubated with 5 μg/ml of the indicated combinations of mAbs to CD28H (R&D MAB83162), 2B4 (BioLegend 329502), NKp46 (BD 557847), NKG2D (R&D MAB139), CD2 (BD 555323), DNAM-1 (BD Biosciences 559787), CD16 (BD 555404) and CD56 (BD 555513) for 15 minutes at room temperature. Resting NK cells were added at an E:T ratio of 1:2, mixed and gently centrifuged at 300 rpm for 1 minute. After 2 hours at 37°C, cells were stained with Live/Dead-NIR (Thermo Fisher), anti–CD56-Bv421 (BD 562751) and anti–CD107a-PE (BD 555801) and analyzed by flow cytometry. Target cell lysis assays were either performed using the ToxiLight Non-Destructive Cytotoxicity BioAssay Kit (Lonza) following the manufacturer’s instruction, or through a flow-based assay. Briefly, NK cells were incubated with PKH67-labeled target cells for 6 hours in IMDM medium with 10% FCS at the indicated E:T ratios. Cells were stained with Live/Dead NIR, and the lysis of target cells were determined by flow cytometry. For CD28H blocking, NK cells were pre-incubated with 10 μg/ml CD28H antibody (R&D Systems) for 15 min before mixing with 221.B7H7 cells. KHYG-1 and NKL cells were rested in complete IMDM medium without IL-2 for 1 day, prior to use in cytotoxicity assays.