TNF and Stroke: Earlier studies suggested that in the very early state after stroke, microglia secrete predominantly toxic factors, such as pro-inflammatory cytokines [e.g., interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6)], and reactive oxygen species (ROS), resulting in the (simplified) classification of so-called M1-like phenotype (14).