TNF and depressive disorder: Within studies using animal models of depression, significant elevations in some critical proinflammatory cytokines including interleukin-1β (IL-1β), interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α) were present, whereas treatments with some putative antidepressant drugs or neuroprotective reagents reduced the levels of these proinflammatory cytokines to varying degrees while also producing antidepressant-like effects [10, 11].