IL2 and depressive disorder: Several inflammatory cytokines, including interleukin (IL)-2, IL-6, and inferteron-alpha, are assumed to generate the kynurenine neurotoxic metabolite in individuals with suicidal tendencies [18–20] and affect the serotonin system [21], which is a pathway well-known for its influence of depressive disorders [22, 23]: dysregulation of the serotonin system by inflammatory cytokines could partially explain suicidal ideation or behavior among people [24].