Cytotypically specific transfecting activity of DNA from C57BL/Ka mouse cells producing thymotropic in contrast to nonthymotropic retroviruses

A comparative study has been made of the susceptibility of fibroblastic cells to transfection by DNA from C57BL/Ka mouse lines producing either fibrotropic or thymotropic retroviruses. DNA isolated from fibroblasts that release a B-ecotropic, fibrotropic virus, BL/Ka(B), was found to transfect fibroblasts of Fv-1bb genotype with release of virus similar to BL/Ka(B). Fv-1nn fibroblasts were also susceptible but expression was delayed, and xenotypic mink lung cells were refractory. In contrast, DNA prepared from a murine T-cell lymphoma line producing a B-ecotropic, thymotropic virus failed to transfect mouse fibroblasts though it transfected a nonproducer T-cell lymphoma line. The data suggest that the Fv-1 and differentiation-specific restriction mechanisms operate at different molecular levels.