IL6 and major depressive disorder: Moreover, immune-inflammatory responses happen in depression similar to IBD with common marker production, including an increase in the levels of proinflammatory cytokines such as interleukin (IL)-6, IL-1, IL-22, IL-17, interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), C-reactive protein (CRP), and Th-17-inducing cytokines [6, 7].