To further confirm that microglia induce A1 reactive astrocytes, we purified microglia by immunopanning and cultured astrocytes in control microglia conditioned medium (MCM) or MCM from microglia that had first been made reactive with LPS. LPS-activated MCM, but not resting MCM, strongly induced A1 reactive astrocytes (Fig. 1a). The level to which these transcripts were induced was comparable to that seen in vivo following systemic LPS injection5 (Extended Data Fig. 3).
