Although immune activation has not been confirmed in the postmortem brain and cerebrospinal fluid of suicides, Snijders et al. reported the protein and mRNA levels of microglial activation markers, such as HLA-DRA, IL6, and IL1β, as well as the inflammatory responses to lipopolysaccharide and dexamethasone in patients with MDD, suggesting that microglia affect homeostatic functions that are essential for brain circuit development and maintenance and may be relevant for suicides [95]. Here, IL1B is linked to major depressive disorder.