(A) C57BL/6J mice were transplanted with BALB/c heart allografts and treated with mATG alone (1 mg i.p. on days 0 and 4), with mATG plus anti-CD122 mAb (0.2 mg i.p. on days –1, 3, 6, 9, and 12), or mATG plus control rat IgG (0.2 mg i.p. on days –1, 3, 6, 9, and 12). The results are representative of 2 experiments with n = 4–5 mice/group/experiment; error bars represent SD. *P < 0.05, ns, P ≥ 0.05 for the comparison of mATG plus anti-CD122 and mATG plus rIgG groups by multiple t tests. (B) B6.WT and B6.IL-15Rα–/– mice were transplanted with BALB/c heart allografts and treated with mATG (1 mg i.p. on days 0 and 4). n = 4–5 mice per group, error bars represent SD. *P < 0.05, ***P < 0.001; ns, P ≥ 0.05 by multiple t tests.