Treatment of NOD mice with anti-TCRβ mAb significantly impairs allogeneic engraftment. NOD mice received vehicle (□; n = 7) or anti-TCRβ mAb (▪; n = 8) on day -3 prior to conditioning with 700 cGy TBI. Allogeneic B10.BR BMCs were subsequently administered, and the mice were monitored for engraftment and chimerism. Chimerism data presented is from 28 days after transplantation. Data represents the means ± SD of combined data obtained from 2 separate experiments.