Up-regulation of activation markers on CD8 cells from chimeric and rejecting mice upon specific stimulation in vivo. (A) 2C/B6 mice were prepared 7 weeks before allo-BMT and received 3 Gy TBI on day −1 and allo-BM transplant on day 0. 2C/B6 mice received a transplant of either L^d+ (B10.A; H-2^a) or L^d− (A.SW or B10.S; H-2^s) BM and were injected with anti-CD154 on day 0 or received L^d+ (B10.A) BM without anti-CD154 (MR1). Activation markers were assessed on days 4 and 7 on 2C CD8⁺ and non-2C CD8⁺ splenocytes by FCM. Statistical analyses were performed with a Mann-Whitney U test to compare the “L^d+ group” with the “L^d− group” or the “L^d+ group” with “L^d+ no MR1 group”: * indicates P < .05; **P < .01; ***P < .001; and NS, not significant. Two experiments are shown for the day-4 analysis (n = 2-5 animals/group per experiment) and 3 experiments are shown for the day-7 analysis (n = 3-5 animals/group per experiment). (B) Expression of activation/memory markers on 2C CD8⁺ and non-2C CD8⁺ splenocytes by FCM is analyzed in 2C/B6 mice that did not receive conditioning or allogeneic BM transplant. The mean percentage of cells expressing the indicated markers 4 days after L^d+ BMT (with anti-CD154) in another experiment is represented by ■. One experiment is shown with 10 animals.