Antigen-specific CTLs are thought to be an important effector mechanism in the elimination of cells infected with a wide number of intracellular pathogens via recognition of pathogen specific antigens complexed with self MHC molecules. CTL induction usually follows antigen processing via endogenous pathway, although exceptions have been reported. Using different antigen delivery systems, we demonstrated that intraperitoneal immunization with formalin-inactivated influenza virus (50ng/mouse) incorporated into poly(DL-lactide-co-glycolide)(DL-PLG) microspheres,
