Characteristics of Mammary Tumor Cultures from Four Mouse Strains Infected with Mammary Tumor Virus

The morphology and production of oncornaviruses in primary cell and explant mammary adenocarcinoma cultures derived from C3Hf, BALB/cNIV, BALB/cfC3H, and C3H mice were characterized. Cultures from the four mouse strains were morphologically similar; they were all epithelial and formed hemicysts and mounds. However, the numbers of cells containing mammary tumor virus (MTV) antigens and the production of cell-free MTV varied greatly among the established cultures. The percentages of MTV-positive cells in the cultures correlated with detection of cell-free MRV; immunodiffusion assays of virions from C3Hf and BALB/cNIV cultures were consistently negative for MTV antigens, whereas virions from BALB/cfC3H and C3H cultures were always positive. Synthesis of murine leukemia virus group-specific, soluble antigens was always observed in C3Hf, BALB/cNIV, and C3H cultures but only rarely observed in BALB/cfC3H cultures.