ICAM1 and glioblastoma: When maintained in serum-containing medium, fewer GBM cells expressed intercellular cell adhesion molecule-1 (ICAM-1) and were less susceptible to lysis by NK cells expressing αLβ2 integrin receptor (LFA-1), mediated through combination of inhibitory KIR–HLA ligand mismatch and diminished activation receptor–ligand interactions compared to cells maintained in stem cell media.