Monday , PM , John Q . Hammons Hall I , ENVIRONMENT AND MANAGEMENT 178

s of papers 41 tumor development, NO production by LPS activated AEC from RSVinjected AR and AP chickens was higher than NO production by LPS activated AEC from age-matched, vehicle-injected AP and AR controls. Macrophages isolated from regressing tumors had higher NO production and exhibited greater cytotoxicity than macrophages isolated from progressing tumors. Based on these data, the inability of AP chickens to regress RSV-induced tumors is not due to a general impairment of macrophage function. Functional differences between macrophages obtained from regressing or progressing tumors suggests a local, tumorspecific impairment of macrophage function in AP chickens.