IL17A and major depressive disorder: Although this study found a reduction in the percentage of IL-17+ CD8+ T cells in depressed patients compared to healthy controls, several other studies have reported elevated levels of IL-17+ T cells in MDD, both in the CD4+ (Th17) and CD8+ (Tc17) subsets, linked to greater symptom severity and an increased risk of autoimmune comorbidities (do Sacramento et al., 2022; Alvarez-Mon et al., 2021a).