Fig. 1 Retroviral gene vector and expression of GFP in CD4+ T lymphocytes. a, Retroviral vector construct pLGFPSN used to transduce CD4+ T lymphocytes. 5′ LTR, long terminal repeat sequences (5′) driving expression of the transgene; SD and SA, splice donor and splice acceptor sequences; SV40, simian virus 40 promoter driving neomycin resistance gene NEO; 3′ LTR, long terminal repeat sequences (3′) containing polyadenylation sequence. b, Phase contrast (left) and fluorescence microscopy of MBP-specific T-lymphocyte blasts after transduction with GFP (green, middle panel). The cells were spread over an object slide and stained with a monoclonal mouse antibody against rat-CD4 (red, right panel). PE-labeled goat anti-mouse serum was used as secondary antibody. c, Activation-dependent GFP expression of CD4+ T lymphocytes. Histograms and dot plots of activated (upper) and resting (lower) transduced and non-transduced T lymphocytes. Dot plots show GFP-transduced T cells stained for CD4. A representative cell line of more than 15 tested is shown.