Recipients of α₄β₇⁺ T cells have increased GVHD mortality and morbidity. Lethally irradiated (1300 cGy) CBA (A) and (1100-1200 cGy) C57BL/6 (B) recipients received transplants with B10.BR TCD-BM (5 × 10⁶) and splenic T cells (0.5-1 × 10⁶). T cells were included in the allograft as unsorted or α₄β₇⁺ CD3⁺ and α₄β₇^– CD3⁺ sorted populations from B10.BR donors. (A-B) Kaplan-Meier and clinical GVHD score (± SEM) curves are shown that represent 4 (BM only), 8 to 11 (BM + T cells), and 13 to 16 (BM + α₄β₇⁺ or α₄β₇^– T cells) recipients per group from 2 combined experiments. Statistical analysis is as follows: (A) left, ○ versus ♦ P = .007, □ versus ♦ P < .0001; right, ○ versus ♦ P < .01, □ versus ♦ P < .01. (B) Left, ○ versus ♦ P = .0179; right, ○ versus ♦ P < .02.