Expression of endogenous Mtv provirus transcripts in BALB/c splenic lymphocytes

The presence of antigen(s) related to the exogenous milk-transmitted murine mammary tumor virus on the surface of BALB/c splenic lymphocytes has been documented previously. Since the BALB/c strain lacks murine mammary tumor virus, the presence of murine mammary tumor virus-related antigen(s) on lymphocytes has been ascribed to expression of germinally transmitted Mtv transcripts and proviruses were characterized to evaluate this hypothesis. Transcripts from genomic size Mtv provirus(es) accumulated in the spleen in an age-dependent manner. Two novel Mtv transcripts of 7.8 and 6.4 kb were observed in the spleen. These observations indicate that the transcriptional and translational expression of an endogenous Mtv occurs in normal cells of the lymphoreticular lineage.