Figure 1.

Neurons expressing cleaved caspase-3 are poorly phagocytosed by microglial cells in ischemic-reperfused regions 24 h after MCAO. A, The characteristic DWI pattern of injury during MCAO is used for animal selection for the study. B–E, K, In contralateral tissue, the few neurons that express cleaved caspase-3 (red) have either multiple contacts with IB4-positive cells (green, arrowheads) or are engulfed by microglia (K). F–I, L, M, In injured tissue, neurons with activated caspase-3 (red) and apoptotic nuclei (blue, bis-benzimide, thin arrows) are abundant, and multiple microglial cells (green) with activated phenotype (thick arrows) are present in proximity to neurons undergoing caspase-3-dependent death. Remarkably few contacts between microglial cells and apoptotic neurons (arrowheads) are seen. J, NeuN (red)/IB4 (green). While microglia are sparse in normal tissue (left bottom corner), they accumulate in penumbra region (right top corner), but relatively few engulf neurons. Cont, Contralateral; Inj, injured. Magnification: B–I, L, M, 63×; J, 20×.