Figure 4.

Confocal light micrographs of CX3CR1^−/− control retinas and 1 day after light exposure (view onto flat mount retinas at different layers). A–C: Microglial cells expressing GFP under control of the Cx3CR1 promoter in the NFL, IPL, and OPL were characterized by small cell bodies and extensive, fine arborizations of their processes. D–G: In the hot spot area, a remarkable lack of microglial cells occurred in the NFL and IPL, whereas the OPL showed activated microglia with shortened, thick processes showing initial signs of phagocytosis (white arrow) and rounded cell bodies. In the hot spot, microglial cells displayed macrophage-like morphology with some cells still displaying glia-like morphology with thickened processes (G). H–J: Microglia in the contralateral unexposed retina (from the light-exposed eye) showed already signs of activation in NFL, IPL, and OPL compared with controls. PRL, photoreceptor layer.