Figure 3.

Microglial phagocytosis in health. Motile, ramified, unchallenged microglia phagocytose neurites (A, dendritic spines, axons) and developmentally apoptotic neurons (B) in physiological conditions in the adult and developing brain. (A) Surface-rendered CX3CR1⁺/EGFP microglia (M; green) from the dorsolateral geniculate nucleus engulfing ipsi- (blue, labeled with cholera-toxin (B) conjugated to Alexa 647) and contralateral (red, labeled labeled with cholera-toxin (B) conjugated to Alexa 594) inputs from retinal ganglion cells at postnatal day 5, when robust pruning occurs. The insert is shown at higher magnification on the right panel. (B) Iba-1 labeled microglia (M; cyan) branching a phagocytic pouch which engulfs a newborn apoptotic/pycnotic cell (A; labeled with the DNA dye DAPI, white), containing immunoreactivity for the neuroblast marker polysialic acid neural cell adhesion molecule (red). The cell is located in the subgranular zone of the hippocampus, where neural stem cells (visualized in nestin-GFP mice) are located and proliferate throughout adulthood. Images (A) and (B) are reprinted with permission from Elsevier. (A) is reprinted from Schafer et al. (2012). (B) is reprinted from Sierra et al. (2010).