Microglia, like astrocytes, play a critical role in synaptic pruning (Aguzzi et al., 2013; Paolicelli et al., 2011; Stephan et al., 2012). Because in vitro synaptosome phagocytosis assays are an established surrogate to study pruning, the ability of iMGLs to phagocytose human synaptosomes (hS) was quantitatively assessed. In comparison to MD-Mφ, iMGL phagocytosis of pHrodo-labeled hS was less robust (Figure 3F, G). However, iMGLs preferentially internalized hS when compared to E. coli particles and normalized to MD-Mφ (Figure S4D, E) supporting the notion that iMGLs and microglia are more polarized toward homeostatic functions than MD-Mφ.
