J774A.1 mouse reticulum cell sarcoma macrophage cell line treated with LPS was stained with Rat Anti-Mouse IL-6 Fluorescein-conjugated Monoclonal Antibody (Catalog # IC406F, filled histogram) or isotype control antibody (Catalog # IC005F, open histogram). To facilitate intracellular staining, cells were fixed with Flow Cytometry Fixation Buffer (Catalog # FC004) and permeabilized with Flow Cytometry Permeabilization/Wash Buffer I (Catalog # FC005). View our protocol for Staining Intracellular Molecules.