CTLA4-CD28 chimera gene modification preferentially affects CD4 T cells over CD8 T cells in vitro. EV or CTC28 retrovirus was transduced into activated OT-II or OT-I T cells with respective antigenic peptide, OVA_323-339 (ISQAVHAAHAEINEAGR, 10 μg/mL) or OVA_257-264 (SIINFEKL, 1 μg/mL). After 2 days of resting in the absence of antigen, GFP-positive T cells were purified by cell sorting. GFP-positive OT-II T cells (A-B) or OT-I T cells (C-D) were stimulated with various concentrations of antigenic peptides in the presence of irradiated splenocytes for 48 hours. IL-2 (A,C) or IFN-γ (B,D) secreted into the culture supernatant was measured by ELISA. Results are representative of 3 independent experiments.