LPS-induced neuronal loss is reduced in the absence of MFG-E8 in vivo. A, LPS injection induces a large increase in activated microglia (stained with isolectin-B4) after 3 d, which recedes by 7 d. Mfge8 knock-out animals show a slight reduction in the number of activated microglia after 3 d. B, C, Neuronal loss after 3 and 7 d is reduced in Mfge8 knock-out animals (MFG-E8−/−) compared with wild-type controls (please note: the apparently smaller neuronal loss at 7 vs 3 d may be a result of tissue contraction; unpublished observation). Data are means ± SEM. D, Expression of the β-galactosidase gene through the Mfge8 promoter in knock-out animals allows for visualization of MFG-E8 expression by β-gal immunostaining (confocal images). MFG-E8 is only expressed in LPS-injected brain, but not on the saline-injected contralateral side (data not shown). Costaining with GFAP and isolectin-B4 reveals expression in both astrocytes and microglia, respectively, but not with the neuronal marker NeuN. Scale bar, 10 μm (all images).