Figure 7 Enhanced activation of T cells from a colorectal cancer patient against autologous tumour cells by the combined CD3ζ‐CD28 costimulatory receptor. Lymphocytes from peripheral blood (PBL) of colorectal cancer patient No 3 were grafted by retroviral gene transfer with the carcinoembryonic antigen (CEA) specific receptors BW431/26‐scFv‐Fc‐ζ.(#439) and BW431/26‐scFv‐Fc‐CD28‐ζ (#607), respectively (see fig 6B). Receptor grafted lymphocytes (PBL‐439; PBL‐607) as well as non‐transduced lymphocytes (PBL) from the same patient (1×10⁵ cells/well) were coincubated for 48 hours with autologous primary CEA⁺ colon cells (A, B), CEA⁺ LS174Τ colorectal tumour cells (C, D), and CEA⁻ Colo201 (E, F) (5×10⁴ cells/well each), respectively. Interferon γ (IFN‐γ) (A, C, E) and interleukin 2 (IL‐2) (B, D, F) were monitored in the culture supernatants by ELISA.