Flow cytometric analysis of human peripheral blood monocytes, resting (open histogram), or treated overnight with 1 µg/mL LPS (filled histogram), were stained with mouse Anti-human IL-15 APC-conjugated Monoclonal Antibody (Product # MA5-23627) or isotype control antibodydata not shown). To facilitate intracellular staining, cells were fixed with Flow Cytometry Fixation Buffer and permeabilized with Flow Cytometry Permeabilization/Wash Buffer I.