Phenotype of Tregs in ADA-SCID patients after different treatments. (A) Representative FACS staining and gating strategy of Tregs in a pediatric HD, GT, and PEG-ADA–treated patient. Total PBMCs were stained for CD4, CD25, CD127, and FOXP3. Gates were established on the basis of isotype-identical monoclonal antibody controls. Treg frequencies are indicated. (B) Percentage of CD25⁺FOXP3⁺ Tregs in the CD4⁺ gate of 22 HD, 11 GT, and 7 PEG-ADA–treated patients. Horizontal bars indicate mean values. *P < .05. **P < .005. (C) Percentage of Tregs identified by the low or absent expression of CD127 in the CD25⁺FOXP3⁺ gate. Horizontal bars indicate mean values. **P < .005.