CD4 and major depressive disorder: - Untreated MDD patients had: ​ ● Lower frequencies of FOXP3 and pSTAT5 in peripheral Treg cells when compared with healthy control and SSRI-treated patients ​ ● Higher in vitro proliferation of CD4+ T cells when compared with healthy control - MDD patients in general had: ​ ● Similar numbers of CD45RA-expressing Treg cells as healthy controls