BALB/c mouse splenocytes were stained with CD4 Monoclonal Antibody, FITC (Product # 11-0042-82) and 0.25 µg of Rat IgG2a kappa Isotype Control, Super Bright 600 (Product # 63-4321-82) (left) or 0.25 µg of CD304 Monoclonal Antibody, Super Bright 600 (right), followed by intracellular staining with FoxP3 Monoclonal Antibody, PE (Product # 12-5773-82) using the Foxp3/Transcription Factor Staining Buffer Set (Product # 00-5523-00) and protocol. Viable CD4+ lymphocytes, as determined by Fixable Viability Dye eFluor® 780 (Product # 65-0865-14), were used for analysis.