Supplementary Material for: Major Depressive Disorder Enhances Th2 and Th17 Cytokines in Patients Suffering from Allergic Rhinitis and Asthma

Introduction: Major depressive disorder (MDD) can impact the severity of allergic rhinitis (AR) and asthma (AA). Here, we evaluated the cytokine production by T-cells from AR and AA patients with or without MDD. The effect of serotonin on the in vitro T-cell response was also evaluated. Methods: The cytokines produced by activated T-cells were measured by Luminex and flow cytometry. In some cell cultures, serotonin was added. Results: MDD not only enhanced the production of Th2- and Th17-related cytokines, but also, the levels of interleukin (IL)-5 and IL-17 were directly correlated with the severity of depression and anxiety symptoms. As compared with AR, the levels of IL-17 were higher and the release of IL-10 was lower in activated T-cell cultures from AA patients, mainly those with MDD. In AA/MDD patients, the severity of anxiety symptoms and lung disease was directly correlated with Th17-like and hybrid Th2/Th17 cells, but inversely correlated with IL-10-secreting CD4⁺ T-cells. Finally, the addition of serotonin reduced the production of Th2- and Th17-related cytokines, but elevated IL-10 secretion in cell cultures from both AR and AA patients. Conclusions: Our findings suggest that not only the occurrence of MDD but also the severity of anxiety symptoms, may adversely affect the outcome of allergic reactions by favoring the production of cytokines implicated in the pathogenesis of AR and AA, a phenomenon that was attenuated by serotonin.