TNF and major depressive disorder: In the last decade, several studies have shown that peripheral low-grade inflammation and neuroinflammation occurs in animal models of depression and at least in some depressed patients, which exhibit higher levels of pro-inflammatory cytokines in serum, such as: interleukin (IL)-4, IL-6, and tumor necrosis factor (TNF)-α (Felger and Lotrich, 2013; Obermanns et al., 2021; Chen et al., 2023), and higher frequencies of pathogenic Th17 proinflammatory cells (Chen et al., 2011; Davami et al., 2016; Beurel and Lowell, 2018).