CD4 and type 1 diabetes mellitus: The first clinical trial using polyclonal Treg cell therapy for patients with T1D dates back to 2012, which showed that infusing ex vivo–expanded autologous CD4+CD127loCD25+ polyclonal Treg cells into newly diagnosed patients with T1D was well tolerated and significantly increased the percentage of circulating Treg cells and improved plasma C-peptide levels (6).