Increased parasite/macrophage ratios leads to an increased intensity of macrophages associated with CFSE marked parasites. The intensity of fluorescence increases in accordace with the number of parasites per macrophage used. Macrophages and parasites were combined as described in Materials and Methods and analyzed for fluorescent intensity using flow cytometry. The data represent the mean flourescent intensity of posive macrophage populations from cultures at each ratio studied. These studies are representative of 4 experiments.