Liddlelow et al. [51] showed that activated microglia induce neurotoxic reactive astrocytes, i.e., glial fibrillary acidic protein (GFAP)- and S100 calcium-binding protein B (S100β)-positive A1 astrocytes with high expression of complement component C3, which are abundant in neurodegenerative diseases. The gene discussed is S100B; the disease is neurodegenerative disease.