TNF and major depressive disorder: For example, preclinical studies showed that Knockout (KO) mice with TNF-α receptor 1 or 2 (TNFR1-2 KO) showed increased depression-like behaviors compared to wild-type mice (Ma et al., 2016) while lateral ventricle injection of TNF-α in mice can induced mood disorders (Haji et al., 2012).