These data and our own work suggest that if there is a role of IL-17 in the onset of depression, this cytokine does not solely originate from CD4 + cells or is produced by alternative cell type (ILC3s, \documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\mathrm{\gamma \delta }$$\end{document}γδ T cells, or others). This evidence concerns the gene CD4 and major depressive disorder.