Detection by Southern blot analysis of a vector sequence in sorted human primary T lymphocytes. Cells infected with GaLV-virions bearing the NTP vector were sorted based on binding of the 20.4 monoclonal antibody. See text for transduction and staining conditions. Genomic DNA was digested with Nhe I. Blots were probed with radiolabeled NTP cDNA. In control lanes (left), the signal corresponds to 1 vector copy per cell in NIH 3T3 fibroblasts (A, noninfected NIH 3T3; B, NTP). In the right lanes, the signal found in noninfected human T lymphocytes (C) and in sorted NTP⁺ lymphocytes (D). The endogenous bands (EB), which differ between mouse and human DNA, show the even loading of each sample.