Southern blot of transgenic tail DNA. (A) Schematic representation of the DNA construct used for transgene derivation. (B) Southern blot analysis of transgenic lines. Tail DNA was extracted, digested with Bgl II, and analyzed by Southern blot as indicated in the Materials and Methods. Transgene levels were quantitated on a BioRad Scanning densitometer (BioRad, Richmond, CA) relative to the endogenous IFN-γ gene (upper band, all lanes).