text: Flow cytometry.
  One million splenocytes were stained with the appropriate primary antibody unconjugated or conjugated to FITC, PE, or APC diluted in stain buffer (PBS with 3% FBS). For BrdU detection, the FITC-BrdU flow kit was used as instructed by the manufacturer (BD Bioscience). Briefly, cells were exposed to EMA (Molecular Probes) for exclusion of dead cells, stained for surface antigens, fixed in paraformaldehyde, and permeabilized with saponin. To expose BrdU epitopes, cells were treated with Dnase and stained with FITC-conjugated anti-BrdU antibody. Flow cytometry was performed on FACScalibur using the CellQuest program (Becton Dickinson). Further analysis was conducted on the Summit v4.2 program (Dako). 
  