In vitro suppression assay and Treg culture
Responder cells were labelled with 6 µM Cell trace violet (Thermo Fisher), then cultured with or without unlabeled Treg cells at a 1:1 ratio for 72 h in the presence of Dynabeads Mouse T-activator CD3/CD28 (1 bead/cells) in round-bottomed 96-well dishes. The proliferation inhibition rate on the responder was calculated as: (1-(Cell trace violet percentage Treg plus responder cells co-culture/responder cells alone)) x 100%.