Distinct PBMC populations were enumerated by flow cytometry, as described (33 (link), 50 (link)). Phenotypic analyses were performed using Abs directed against CD3 (clone SP34-2), CD4 (L200), CD8 (RPA-T8), CD14 (M5E2), CD20 (2H2), CD45RA (5H9), CD56 (MY31) and CD127 (HIL-7R-M21) from BD Pharmingen (Franklin Lakes, NJ). Anti-CD159a (NKG2A) (Z199) was from Beckman Coulter and anti-CD28 (CD28.2) from Biolegend (San Diego, CA). Anti-CD25 (BC96) was from eBioscience (San Diego, CA) and anti-CD62L (SK11) from Becton Dickinson (Franklin Lakes, NJ). Data were acquired on a LSR II or LSR Fortessa (BD Bioscience) and analyzed with FlowJo software.