Gating strategy for CD4 T-cell proliferation using carboxy fluorescein succinimidyl ester (CFSE) dye. (A) Total lymphocyte gate, (B) live/dead lymphocytes, (C) the CD3+ CD4+ T-cell gate, (D) unlabeled CD3+ CD4+ T-cells, (E) unstimulated CD3+ CD4+ T-cells (CFSE negative control) and (F) CD4 T-cell proliferation (CD3+ CD4+ CFSE−). T-cells, with PHA stimulation as a positive control.