Donor (Ly-5.2⁺) bone marrow cells contain integrated provirus based on Southern analysis.

Clonal assays to determine the number of proviral integrants per cell were done on isolated day 8 CFU-S colonies and from single stem cells FACS-sorted onto a stromal feeder layer (AC-6) that supports cell growth and expansion so that sufficient amounts of DNA could be isolated for analysis. B, T, and myeloid cell populations were purified by magnetic bead enrichment as described previously. The Southern blot was probed with a randomly primed GFP fragment.