L-NIL is a relatively selective inhibitor of iNOS. It exhibits IC50 values of 0.4-3.3 µM for iNOS as opposed to 8-38 and 17-92 µM for eNOS and nNOS, respectively. L-NIL effectively inhibits iNOS both in vitro and in vivo. L-NIL has been used to demonstrate a critical role for iNOS in the immune response to infection...