TS1 T_N and T_CM cause severe GVHD whereas TS1 T_EM cause only mild GVHD. HA104 mice received 750cGy and 8 × 10⁶ RAG^−/− BM cells alone or in combination with 9000 or 3000 TS1 T_N, T_CM or T_EM. Mice were killed at day 60 and tissues were taken for histopathologic analysis. Survival and weight loss are shown in panel A. P < .0001 comparing weight loss in recipients of T_N or T_CM vs recipients of BM alone on days 7 to 60. P < .0001 comparing weight loss in T_EM vs T_N recipients on days 13-60. P < .0001 on days 9-23 and P < .05 on days 46-60 comparing weight loss in recipients of 9000 T_EM vs recipients of BM alone. Weight data in recipients of 3000 TS1 cells are representative of > 3 independent experiments; weight loss in recipients of 9000 TS1 T_EM is from one experiment. Mice were killed at the conclusion of the experiment and histopathology was scored in panel B. Pathology is from one experiment with n = 9-10 per group. See text for details.