Fig. 5.

Time-dependent loss of recall proliferation by donor-reactive tolerant T cells with prolonged graft antigen exposure. Relative recovery of TCR75 cells in rechallenged vs. nonrechallenged mice 5 to 6 d post rechallenge with DST in secondary naïve hosts. To account for any possible impact of senescence, all groups were normalized to recall proliferation by TCR75 cells harvested from time-matched untransplanted controls that received DST on the same day their matched experimental group received a transplant (DST = 100). These values are plotted against the number of days that the hearts (and DST for the respective control mice) were present in the animals. Tolerant animals are the same as those shown in Figs. 1, 3, and 4. Tol d7 graft removal (7-d exposure to alloantigen, analysis on d35) n = 7; Tol d21 graft removal (21-d exposure to alloantigen, analysis on d35) n = 3; Tol d35 (35-d exposure to alloantigen, analysis on d35) n = 15; Tol d42 (42-d exposure to alloantigen, analysis on d42) n = 4; Tol d60 (60-d exposure to alloantigen, analysis on d60) n = 7. These data are from 8 independent experiments. The relative recovery of the cells was negatively correlated with the duration of antigen exposure, Pearson’s r = −0.73, ****P < 0.0001.