2.1. ISD017, ISD017-derivatives, H-151, RU.521, and treatment of cells

ISD017 and derived peptides were obtained from Schafer-N. H-151 and RU.521 were obtained from InvivoGen. To dissolve ISD017 a panel of solvents were tested, namely: H₂O; 0.9% NaCl; TBS (pH 7.3); PBS (pH 7.4); HEPES; PBS (pH7.4) + 1 M NaOH. For the latter, which was most successful, 194 uL of PBS mixed with 6 uL 1 M NaOH was added to 1 mg ISD017 or mutant peptides. H-151 was dissolved in DMSO and diluted in PBS + 10% tween80, and RU.521 was dissolved in DMSO. For in vitro experiments, primary cells and cell lines were treated with cGAS/STING antagonists one h prior to stimulation unless otherwise stated. The antagonists were administered by direct addition to the culture medium. For stimulations, we used 60‐mer dsDNA (DNA technology) [47], 2′3′ cGAMP, and poly(I:C) (both from InvivoGen). The agonists were delivered with Lipofectamine 2000 (ThermoFischer). Liposomes were prepared as described using lipid blends containing DOTAP, DOPE and lissamine–rhodamine DOPE in the w/w/w ratio 1/1/0.1 Avanti Polar Lipids [48].