Specific lysis by chA21-28z chimeric antigen receptor T cells in vitro . (A) Antigen-specific killing of HER2+ tumor cells by chA21-28z chimeric antigen receptor (CAR) T cells was determined using a 4-hour chromium-51 release assay at the indicated effector-to-target (E/T) ratio. Nontransduced (NT) T cells and HER2− tumor cells served as controls. (B) NT or chA21-28z CAR T cells were seeded into cultures of SKOV3 cells expressing HER2. After about 24 hours in coculture, formation of T-cell clusters and elimination of the SKOV3 monolayer were visible.