Studies on cell lines derived from calf, thymic and skin forms of bovine lymphosarcoma.

The etiology of sporadic bovine leukosis (SBL) is not known. Long-term monolayer cultures were made from calf (CLS), thymic (TLS) and skin (SLS) forms, and serological tests, electron microscopic observations and reverse transcriptase assays were employed for the detection of an etiological agent. Bovine leukosis virus (BLV) antigen and reverse transcriptase activities remained negative in cultures from SBL cases. Treatment of a culture from CLS 3178 with 5'-iodo-2'-deoxyuridine and dexamethasone resulted in production of BLV which may have been acquired from the BLV-infected dam of CLS 3178, and in an alteration of cell morphology. Focus formation in monolayer cultures and colony formation in soft agar cultures were observed in this treated cell line. Human fetal lung fibroblast cells cocultivated with the cultures from SBL resulted in rapid proliferation of cells with an increased focus formation.