Description: Brefeldin A is an inhibitor of intracellular protein transport. Incubation of cells in culture with Brefeldin A leads to blockade of protein transport to the Golgi complex (GC) and accumulation of proteins in the endoplasmic reticulum (ER). Addition of Brefeldin A during the last hours of in vitro activation of cells results in enhanced detection of intracellular cytokines. Brefeldin A is effective for enhanced detection of a majority of mouse and human intracellular cytokines; however, it is advised that the investigators evaluate the use and efficacy of this reagent as well as other protein transport inhibitors such as Monensin in their specific assay system.