Differential activation and granzyme B expression in purified human naive and memory CD4⁺ T lymphocytes. (A) FACS plot demonstrating the gates used to flow-purify CD4⁺CD45RA⁺ naive and CD4⁺CD45RO⁺ memory T lymphocytes. (B) Representative FACS plots demonstrating the differential kinetics of activation (FSC and SSC) between naive and memory CD4⁺ T lymphocytes at days 2 and 4. Modes of activation are indicated above each column of FACS plots. (C) Summary of granzyme B expression between naive and memory CD4⁺ T lymphocytes at days 2 and 4. T-cell subsets and modes of activation are indicated below each column. Data shown are representative of 3 or more independent donor samples.