NOS2 and infection: The four-fold increase in the L-arginine internal pool observed in arg− and arg−/+argΔSKL mutants, associated with their impaired infectivity, could indicate that one of the roles of ARG during infection is modulating the availability of L-arginine, and consequently regulating the host immune response via the iNOS pathway [8], [9] or the MAPK pathway, which recently was indicated as another L-arginine-dependent pathway [26].