ATG negatively affects SRC activity whereas OKT3 does not. (A) Human CD45⁺ cell engraftment in the BM of NSG mice 8 weeks after injection of purified UCB CD34⁺ cells was not affected by pretreatment with OKT3 but was completely eliminated by ATG. (B) The lineage distribution of these BM grafts was also not affected by OKT3 relative to controls. (C) Normal donor human PB-NK cells engrafted NSGS mice and were present at high levels in the PB with or without OKT3 pretreatment. Cell preparations were incubated with a low (LD) or high dose (HD) of OKT3 in vitro or mice were injected (IP) with a single 10-mg/kg dose of antibody 24 hours after cell transfer.