Physiological consequence of CD80 acquisition by T cells in vivo. (A) PKH-stained CD4⁺CD80^{acq hi} T cells were adoptively transferred into PCC/TCR-Tg mice, and the proliferative response of these cells was measured by BrdU incorporation 2 days after adoptive transfer of these cells. PKH-positive and -negative cells were analyzed for BrdU incorporation using 3-color FACS analysis. (B) A total of 6 × 10⁶ CFSE-stained CD4⁺CD80^{acq hi} T cells were adoptively transferred into PCC/TCR-Tg mice. Proliferative response of CFSE-stained CD4⁺CD80^{acq hi} T cells was examined 24 and 48 hours after adoptive transfer using FACS analysis. Percentages are the percent positive Brd U positive T cells.