Gliotoxin is an immunosuppressive mycotoxin produced by pathogenic strains of Aspergillus and other fungi with diverse biological activities.[1],[2],[3],[4],[5],[6],[7],[8] It inhibits 20S proteasomal chymotrypsin activity (IC50 = 10 μM), blocking the degradation of IκBα and preventing the activation of NF-κB.[2],[3] Gliotoxin induces apoptosis in monocytes and dendritic cells and reduces phagocytosis by neutrophils.[4],[5]It suppresses viral infection by Nipah and Hendra virus in HEK293T cells (IC50s = 149 and 579 nM, respectively).[6] Under reducing conditions, gliotoxin inhibits leukotriene A4 hydrolase epoxide hydrolase activity, but not aminopeptidase activity, and leukotriene B4 synthesis in neutrophils and monocytes.[7] In vivo, gliotoxin (5 mg/kg) reduces LTB4 plasma levels and blocks peritoneal neutrophil infiltration in a mouse model of peritonitis induced by zymosan A. It also inhibits geranylgeranyltransferase I and farnesyltransferase (IC50s = 17 and 80 μM, respectively).[8]