NOS2 and infection: While NOS was upregulated 1- to 2-fold following STS (Fig. 5B) (that correlated with an approximately 0.2-fold increase in total cellular NO concentration [Fig. 1F]), infection of these STS flies with E coli led to a 35-fold increase in NOS expression in wild-type flies that was not observed in rel flies (Fig. 5B).