BCL-2 expression in radioresistant populations. H2K-BCL-2/1038 transgenic and wild-type mice (littermates) were analyzed for expression of endogenous (mBCL-2) and transgenic (hBCL-2) protein 2 days after lethal irradiation (9.2-Gy split dose). Staining of CD4⁺ splenocytes is depicted. Filled gray histogram, staining in untreated animals; thick line, staining after lethal irradiation. (Top) Background staining of the secondary antibody (goat–anti-hamster-FITC) used to detect hamster–anti-mouse BCL-2 or autofluorescence (mouse–anti-human BCL-2 was FITC-conjugated). (Left) Mouse BCL-2 expression in a wild-type mouse. (Middle) Mouse BCL-2 expression in a H2K-BCL-2 transgenic mouse. (Right) Expression of the transgene (human BCL-2) in a H2K-BCL-2 transgenic mouse. One representative experiment (out of four) is shown.