Brefeldin A (BFA) is a protein transport inhibitor commonly used to enhance intracellular cytokine staining signals by blocking transport processes during cell activation. Especially useful for the intracellular staining of cytokines, BFA leads to the accumulation of most cytokines at the Golgi Complex/Endoplasmic Reticulum (see Jung, et al., 1993). 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 (see references below for additional information). Brefeldin A Solution is supplied as a 1,000X solution, which should be diluted to 1X in cell culture medium.