Live/Dead staining of cells

Prior to Live/dead staining, cells were washed three times with ice-cold 1×DPBS by spinning at 700× g in a 4 °C centrifuge. Live/Dead stain was prepared by mixing 2 μl of fixable far-red dead cell stain stock solution (Invitrogen/Thermo Fisher, Waltham, MA, USA) with one ml 1×DPBS. Cells were suspended in 50 μl of Live/Dead stain and then incubated at 4 °C for 30 min in the dark. Excess Live/Dead stain was removed by washing cells once in 1xDPSB, and then once in FACs buffer consisting of 1×DPBS and 5%FBS.