Figure 1.

Possible means of synapse modification or elimination by quiescent microglia. In (A), a synapse between an axon terminal (blue) and a dendritic spine (pink) is simultaneously contacted by an astrocytic (green) and microglial (taupe) process. Note the astrocytic and microglial contacts with the synaptic cleft (arrowheads) and the pocket of microglia-associated extracellular space (asterisk), which suggests microglial remodeling of the extracellular environment in the vicinity of synapses. Surrounding elements of neuropil are shown in grey. (B) Microglial process displaying end-feet morphological specializations. Here, these end-feet contact a dendritic spine (end-foot 1) and an axon terminal (end-foot 2), at two different synapses. Such direct cell-cell interaction between microglia and synaptic elements could contribute to local remodeling of the actin cytoskeleton during episodes of plasticity. (C) Engulfment by a microglial process of an intact synapse between an axon terminal and a dendritic spine suggesting microglial phagocytosis of synaptic elements during experience-dependent plasticity.