BDNF and ischemic stroke: In contrast to the M1 phenotype, the M2 phenotype generates anti-inflammatory cytokines, such as transforming growth factor (TGF)-β, IL-4, IL-10 and IL-13, as well as increases the levels of growth factors, such as vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF) for neuronal repair at the late stage of ischemic stroke (Qin et al., 2019; Lyu et al., 2021).