For example, it has been reported that phagocytic microglia in rats carrying ALS-linked mutations surround motor neurons already at the presymptomatic stage of the disease (i.e., preceding neuronal loss) [32], but microglial activation markers, such as CD11b and MHC class II upregulation, and TNF-α and MCP-1/CCL2 positivity, were used as surrogate markers of phagocytosis without formally probing the phagocytic function of microglia. This evidence concerns the gene CCL2 and amyotrophic lateral sclerosis.