Brain-resident microglia are first activated within an hour of ischemic stroke (Planas, 2018): M1-type microglia secrete pro-inflammatory factors, including interleukin-1 (IL-1), IL-6, tumor necrosis factor α (TNF-α), and MMP-9, while M2-type microglia produce IL-10, transforming growth factor β (TGF-β), insulin-like growth factor, and VEGF, which are synergistically involved in the process of angiogenesis (Dabrowska et al., 2019). Here, TNF is linked to ischemic stroke.