NOS2 and infection: We observed that infection of BMMΦ with the more virulent T. cruzi isolate (QRO) importantly diminished NOS2 expression and nitric oxide (NO) production in CAMΦ, allowing parasite survival, while infection with the less virulent isolate (CI2) did not diminish NOS2 activity and NO production in CAMΦ to a great extent, which resulted in parasite killing.