Use of EGFRt as a target for Erbitux-mediated ADCC of engineered cells. (A) ⁵¹Cr-labeled huEGFRt-selected T cells (inset depicts huEGFRt expression) were mixed with 1 μg/mL of Erbitux or Rituxan as a negative control before addition of GM-CSF–stimulated human PBMCs as effectors. The percentage ⁵¹Cr-release was then determined after a 4-hour incubation. Data are representative of 2 separate experiments. (B) NOD/scid mice were inoculated intravenously with ffLuc⁺huEGFRt⁺ CTLL-2 cells. On successful engraftment (day 0), the mice were divided into 2 groups (n = 5) and then treated with either Erbitux (Ctxmb) or Rituxan (Rtxn) intraperitoneally daily for 6 days. Data are ± SE; total flux levels of luciferase activity were measured by Xenogen imaging. *P = .0159, the flux of Erbitux versus Rituxan-treated mice at day 6 using the Mann-Whitney test. (C) Representative bioluminescence images of NOD/scid mice from (B) at day 6.