FLT1 and age-related macular degeneration: Indeed, circulating human monocytes, which participate in mononuclear phagocyte infiltration in AMD, express VEGFR1 but not VEGFR2, and a VEGFR1-neutralizing monoclonal antibody has been shown to significantly suppress VEGF-A-induced migration of microglial cells (Sawano et al., 2001).