WT or CD70-/- C57BL/6 mice received 965 cGy irradiation on day -1 and were subsequently transplanted day 0 with 4×106 BALB/c BM ± PanT. For early time points (days 3, 4, and 5), 5×106 PanT were injected in order to harvest sufficient T cells for reliable analysis. For the late time point (day 7), 2×106 PanT were injected to minimize untimely host lethality. At days 3, 4, 5, and 7 following allo-HCT, spleens were harvested, counted and stained for flow cytometry. Absolute numbers of donor-derived CD4+ (A) and CD8+ (B) T cells in WT and CD70-/- hosts receiving BM + PanT were acquired via the following equation: (total number of splenocytes) × (percentage of live H-2Kd+CD3+CD4+ or H-2Kd+CD3+CD8+ T cells). Summary data from three individual experiments are shown (n=2-5 for each time point). Statistical significance was analyzed by student's t test. **P<.01; ***P<.001.