The role of arginase in the immune response

Arginase activity — mainly known for its involvement in urea formation in the liver — inhibits DNA synthesis in cultured mammalian cells1. Arginase is synthesised and released by activated macrophages mediating immunosuppression during mixed leucocyte culture2 and may be implicated in macrophage cytotoxicity during the anti-tumor3, anti-parasite4 and anti-viral5 responses. Here Elke Schneider and Michel Dy discuss these aspects of arginase activity as well as more recent indications that arginase may be involved in the cell differentiation and/or proliferation taking place during the immune responses6,7. A lymphokine with arginase-enhancing activity has been identified. By producing ornithine, arginase provides the unique precursor of polyamines which are essential for DNA synthesis8.