Morphology and surface phenotypes of stimulated and un-stimulated CD4+ T cells. A: CD4 + T cells stimulated with PHA/IL-2 (“P”) or CD3/CD28 coated beads (“B”) were observed on day 0 (un-stimulated (“R”)), day 3 and day 6. B: Flow cytometric analysis of cell surface phenotypes. “R”, “P” and “B” cells were stained with antibodies to CD25 (FITC), CD69 (PE-Cy5) and CD45RO (FITC). Numbers indicate the percentage of each subset. A majority population of cells emerged in “B” cells which expressed CD25, CD69 and CD45RO. We did the experiments in 19 biological replicates.