Fig 1: ILT2 blockade promotes natural killer (NK) cell-mediated cytotoxicity against glioblastoma. The cytotoxic activity of pretreated peripheral blood mononuclear cells (PBMCs) from healthy donors against glioblastoma cells was evaluated at three different E:T (effector:target) ratios by calcein-AM staining. Graphs depict the percentage of specific lysis (mean ± SEM). (A) PBMCs from healthy donors (n = 10) were treated with anti-ILT2 blocking antibodies or control IgG (10 µg/mL) for 72 h and then cocultured with glioblastoma cell lines for 4 h. (B) ILT2 binding was evaluated on glioblastoma cells after HLA-(A,B,C), HLA-E, or HLA-G blockade by flow cytometry (n = 3). Histograms illustrate a representative experiment employing LN-18 cells. Bars correspond to normalized MFI ± SEM. (C) PBMCs from healthy donors (n = 8) were cocultured with LN-18 cells in the presence of anti-ILT2 blocking antibodies or control IgG (10 µg/mL) for 24 h, followed by coculture with fresh LN-18 cells for 4 h. (D) PBMCs from healthy donors (n = 6) were treated with anti-ILT2 blocking antibodies or control IgG (10 µg/mL) for 72 h. LN-18 cells were treated with temozolomide (TMZ, 100 µM) for 72 h. Afterwards, cells were cocultured for 4 h. *p < 0.05; **p < 0.01