The role of Th17 cells in the pathophysiology of pregnancy and perinatal mood and anxiety disorders.

T cells play a key role in adaptive immune responses, and shifts among T cell classes occur in normal pregnancy. There is evidence for the role of T17 cells and dysregulation of the T17/T cell balance in morbidities and autoimmune diseases during pregnancy. Because T17 responses may play a role in depression and anxiety outside of pregnancy, we hypothesize that T17 responses and the balance of T17/T activity may also contribute to the development of depression and anxiety during pregnancy. To explore this hypothesis, this review has three main aims: 1) to evaluate systematically the role of T17 cells and cytokines during pregnancy; 2) to compare changes in the ratio of T17/T cells during pregnancy morbidities with the changes that occur in depression and anxiety outside of pregnancy; and 3) to provide a basis for further research on T17 cells in perinatal mood and anxiety disorders, with an eye toward the development of novel therapeutics. We also review the limited literature concerning perinatal mood and anxiety disorders, and hypothesize about the potential role of T17 cells in these illnesses. Understanding the pathophysiology of perinatal mood and anxiety disorders will aid development of novel therapeutics that address immunological mechanisms, in addition to the serotonin system, which are targetable molecules in treating depression and anxiety during pregnancy.