Mouse splenocytes, untreated (open histogram), or treated with LPS for 48 hours (filled histogram) were stained with Rat Anti-Mouse IL-1 beta /IL-1F2 Fluorescein-conjugated Monoclonal Antibody (Catalog # IC4013F, filled histogram) or isotype control antibody (Catalog # IC013F, data not shown). Histograms were gated on blasting splenocytes. 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.