For example activated macrophage-derived NO or NO donors such as SNAP reducedTrypanosoma brucei proliferationin vitro175,176 whereas endogenous iNOS-derived NO suppressed protozoa-antigen specific T-cell proliferative responses and so worsened infection, at least in infected mice.176 Intracellular protozoal infections are unlikely to be affected in this manner since macrophage-derived NO would be able to act directly on pathogens such asLeishmania major.177. Here, NOS2 is linked to infection.