CX3CR1 and infection: In contrast, CX3CR1, reported by GFP in Cx3cr1gfp/+ mice, was expressed by all Ly6Chi monocytic cells in the liver of infected Cx3cr1gfp/+ mice (data not shown), and in these animals the majority of hepatic MerTK+CD64+ cells were also GFP+ (Fig. 3B), indicating a significant contribution of monocytes to the macrophage pool during infection.