IL4 and major depressive disorder: In blood samples, the plasma concentrations of different cytokines (IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, TNFα, epidermal growth factor (EGF), and vascular endothelial growth factor (VEGF)) were analyzed using an ELISA assay, in suicide attempters with a history of MDD.