SAMEN-PL5.04 retroviral vector. The T-cell receptor (TCR) α and β chains molecularly cloned from the PL5.04 cytotoxic T-cell lymphocyte (CTL) clone were transferred into the SAMEN vector, and infectious retroviral supernatant produced by transfection of the Phoenix cell line. Expression for the TCR α chain is from the 5′ long terminal repeat (LTR), whereas the TCR β chain is expressed from the SRα promoter, a strong promoter derived from human T-cell leukemia virus (HTLV)-I and SV-40 sequences. The neomycin resistance gene is expressed on the same transcript as the TCR α chain by virtue of an internal ribosome entry site (IRES). SD, splice donor site; SA, splice acceptor site; ψ+ is the retroviral packaging signal17. Both the α and β chain are flanked by restriction endonuclease sites allowing the rapid introduction of new TCR sequences.