Detection of IRF5 in Human PBMCs Monocytes by Flow Cytometry. Human peripheral blood monocytes were stained with Sheep Anti-Human IRF5 PE-conjugated Antigen Affinity-purified Polyclonal Antibody (Catalog # IC4508P, filled histogram) or isotype control antibody (Catalog # IC016P , 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 .