Elevated IL-17 and TGF-β Serum Levels: A Positive Correlation between T-helper 17 Cell-Related Pro-Inflammatory Responses with Major Depressive Disorder

Introduction: Depression is a mental disorder that highly associated with immune system.&nbsp;Therefore, this study compares the serum concentrations of IL-21, IL-17, and transforming&nbsp;growth factor &beta; (TGF-&beta;) between patients with major depressive disorder and healthy controls. Methods: Blood samples were collected from 41 patients with major depressive disorder and&nbsp;40 healthy age-matched controls with no history of malignancies or autoimmune disorders. The&nbsp;subjects were interviewed face to face according to DSM-IV diagnostic criteria. Depression&nbsp;score was measured using completed Beck Depression Inventory in both groups. The serum&nbsp;concentrations of IL-21, IL-17, and TGF-&beta; were assessed using ELISA. Results: The mean score of Beck Depression score in the patient and control groups was&nbsp;35.4&plusmn;5.5 and 11.1&plusmn;2.3. IL-17 serum concentrations in the patients and the control group were&nbsp;10.03&plusmn;0.6 and 7.6&plusmn;0.6 pg/mL, respectively (P=0.0002). TGF-&beta; level in the patients group was&nbsp;significantly higher than compare to the control group; 336.7&plusmn;20.19 vs. 174.8&plusmn;27.20 pg/mL,&nbsp;(P<0.0001). However, the level of IL-21 was not statistically different between the two groups&nbsp;84.30&plusmn;4.57 vs. 84.12&plusmn;4.15 pg/mL (P>0.05). Conclusion: Considering pro-inflammatory cytokines, current results support the associationof inflammatory response and depressive disorder. So, it seems that pro-inflammatory factors&nbsp;profile can be used as indicator in following of depression progress and its treatment impacts.