PD-1 is an important immune checkpoint inhibitor that shows great promise in the clinic, particularly for melanoma and lung cancers. Since PD-1 is also expressed on infiltrating Tregs in glioblastoma, we sought to better understand the role of PD-1 on these infiltrating Tregs. To this end, we performed functional and transcriptional profiling using Tregs isolated from healthy donors and glioblastoma patients (from both tumors and blood).