Microglia respond to inflammatory molecules, e.g., TNF and CSF1, released from activated astrocytes and to aggregated proteins that accumulate in the CNS in neurodegenerative diseases, e.g., mutant SOD1 in ALS, beta-amyloid in Alzheimer’s disease, and alpha-synuclein in Parkinson’s disease. Here, SOD1 is linked to amyotrophic lateral sclerosis.