Donor Th2R cell abrogation of rejection reduces allospecific host T-cell effector function. BALB/c-into-B6 transplantation consisted of lethal irradiation (1100 cGy; day −2), and some combination, as indicated, of host T cells (day −1; 1:1 mix of 2C TCR-transgenic and CD45.1-congenic WT T cells; each population, 0.05 × 10⁶ cells); and BALB/c donor BM cells with or without donor Th2R cells (day 0). The ratio of donor Th2 cells to host T cells was either 100:1 (“BM/Th2R_lo”) or 500:1 (“BM/Th2R_hi”). On days 11 and 21 after BMT, spleen, and BM cells were isolated and stimulated with syngeneic (B6) or allogeneic (BALB/c) DCs for 24 hours. The total number of host Vβ8⁺CD8⁺ cells or CD4⁺CD45.1⁺ cells producing allospecific IFN-γ in the spleen (panels A and B, respectively) and BM (panels C and D, respectively) was evaluated by flow cytometry at both day 11 after BMT (left panels) and day 21 after BMT (right panels). Results shown are mean plus or minus SEM of n = 10 per cohort. *P < .05; **P < .01; ***P < .001.