Higher expression of IL-1β, IL-6, MIF and TNF-α and lower expression of IL-4 in patients with MDD compared with controls.IL-β, TNF-α and MIF expression predicted antidepressant response.Significant decrease in IL-6 expression after 8 weeks of antidepressant treatment (escitalopram or nortriptyline) in responders only. Here, IL6 is linked to major depressive disorder.