Anti-T–cell antibodies prevent GVHD. (A) Survival of sublethally irradiated NSG mice was monitored after tail vein injection of 20 million normal donor human PB MNCs/mouse. (B) Weights of the mice from A showed a characteristic decline over time. (C) PB from BU-conditioned NSGS and NRGS mice injected with 13 to 17 million antibody pretreated UCB cells showed significant human T cells only in control mouse PB 2 weeks after injection. (D) Survival of mice in C was monitored. (E) Analysis of the week 2 PB samples analyzed in C highlight the potential non-T–cell specific effects of ATG.