*2.10. FACS*

HEK293 cells were trypsinized, resuspended in FACS buffer (PBS, 1% FCS, 2 mM EDTA, 0.02% sodium azide) and fixed immediately by adding an equal volume of pre-warmed (to 37 ◦C) BD Cellfix (BD Biosciences). Cells were permeabilized by adding chilled BD Phosflow Perm Buffer III (BD Biosciences) drop-by-drop while vortexing. Intracellular staining was performed with anti-p-STAT1 antibody (mouse anti-human p-STAT1, BD clone 4a (RUO)). Cellular debris and doublets were gated out using forward scatter and side scatter channels and 50,000 live single cells were analyzed per sample using an Attune Flow Cytometer (ThermoFisher Scientific).
