Fluorochrome-labeled inhibitors of caspase-1 require membrane permeabilization to efficiently access caspase-1 in macrophages.

Caspase-1 location in cells has been studied with fluorochrome-labeled inhibitors of caspase-1 (FLICA reagents). We report that FLICA reagents have limited cell-membrane permeability. This impacts experimental design as cells with intact membranes, including caspase-1 knockout cells, are not appropriate controls for cells with inflammasome-induced gasdermin D membrane pores.