The cytokine IL‐17A as a marker of treatment resistance in major depressive disorder?

Major depression is a complex disease and—among others, inflammation appears to play an important role in its pathophysiology. In this study, we investigated a broad range of cytokines in depressed patients. Plasma levels of interleukin (IL)‐12/ IL‐23p40, IL‐15, IL‐16, IL‐17A, IL‐1α, IL‐7, tumor necrosis factorβ and vascular endothelial growth factor were compared in 48 patients suffering from major depression before, after one and after six weeks of antidepressive treatment in relation to therapy response. Interestingly, the level of IL‐17A turned out to rise significantly in the non‐responder group compared to responder during antidepressive treatment. IL‐17A is a pro‐inflammatory cytokine that initiates the production of other cytokines, thereby inducing and mediating immune response. It is also involved in allergic and autoimmune‐related diseases. The database investigating the role of IL‐17A in major depressive disorder has grown within the last few years comparing levels of this cytokine in depressed patients versus healthy subjects. However, little is known about the expression of IL‐17A during the course of antidepressive treatment. In summary, our study provides valuable evidence that this cytokine might serve as a marker of therapy resistance to antidepressants