To compare the role of various stimulation and cell culture protocols on the activation and anti-tumor function of CAR T cells, we generated primary human T cells that express a CAR with an FRP5 scFv-based HER2-specific recognition domain, an IgG1 short hinge, a CD28 transmembrane domain, and CD28.CD3ζ (HER2.CD28.z) or 41BB.CD3ζ (HER2.41BB.z) costimulatory and effector endodomains (Figure 1a). The gene discussed is CD28; the disease is neoplasm.