IL6 and major depressive disorder: Increased cytokine mobilization in the peripheral blood, for example, increased levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6), is a common immunological finding in MDD patients70, 71 or a subgroup thereof.72 Inflammation-related genes have also been found to be upregulated in postmortem frontal cortex of medication-free MDD patients,73 suggesting focal inflammatory processes in the CNS.