The importance of NO production and its release in pathogen-directed defense mechanisms has been confirmed by the effect of NOS inhibitors (Boom, 1996; Flynn et al., 1998; Sciorati et al., 1999) and NOS knock-out mice on enhancing the severity of infection and of exacerbations in-vivo and ex-vivo (Cooper et al., 2000; Kuo et al., 2000). This evidence concerns the gene NOS2 and infection.