Effect of coadministration of donor splenocytes plus a single injection of MR1 on cardiac allograft survival in WT, STAT4^–/–, and STAT6^–/– recipients. C57BL/6 hearts were transplanted into WT, STAT4^–/–, or STAT6^–/– BALB/c recipients. Recipients were treated with MR1 (250 μg intraperitoneally) plus 5 × 10⁶ donor splenocytes intravenously on the day of transplantation. There were no significant differences between the three recipient types.