The idea that immune system activation may also be associated with stress and depression pathophysiology (Figure 1) is supported by clinical findings showing elevated blood levels of proinflammatory cytokines (PICs), primarily interleukin- (IL-) 1β, IL-6, and tumor necrosis factor alpha (TNFα), in depressed patients [41, 42]. The gene discussed is TNF; the disease is major depressive disorder.