Monensin is a protein transport inhibitor that increases intracellular cytokine staining signals by blocking transport processes during activation of a cell. This leads to the accumulation of most cytokines at the Golgi Complex/Endoplasmic Reticulum, and makes Monensin useful in intracellular staining of cytokines. Optimal conditions for use are cell type and time-dependent. Typically, protein transport inhibitors are included during in vitro cell activation cultures for 4-24 hours prior to harvest. Monensin Solution is supplied as a 1,000X solution, which should be diluted to 1X in cell culture medium.