Allospecific host T cells adopt a Th2 cytokine phenotype during rejection abrogation by donor Th2 cells. BALB/c-into-B6 transplantation consisted of lethal host irradiation (1100 cGy; day −2), and a 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”). Spleen cells were harvested on day 8 after BMT (A) and day 11 after BMT (B), and allospecific host T cells were purified by flow sorting for H-2K^b+CD8⁺Vβ8⁺CD45.1⁻ cells. Purified host T cells were stimulated with anti–CD3/CD28-coated beads for 24 hours; resultant supernatants were tested for cytokine content (pg/mL). Results shown are mean plus or minus SEM of n = 5 per cohort for each time point. *P < .05; **P < .01; ***P < .001.