Differentiation analysis of bovine T-lymphosarcoma.

The tumor cells from three different types (calf, skin and thymic) of bovine lymphosarcoma identified as sporadic bovine leukosis (SBL) were transplanted to nude mice and established as lymphoid tumor lines. To clarify the T-cell lineage, clonality and differentiation stage, these cell lines were examined for the immunophenotypic profile, the expression and the gene rearrangement of T-cell receptor (TCR) genes. The tumor cells from all three types showed alpha-naphthyl acetate esterase-positive staining and the absence of surface immunoglobulin (sIg). Moreover, the tumor cells appeared to be all BoCD5+ BoCD6+ BoCD4- BoCD8- cells in the FACS analysis with mAbs. Rearrangement of TCR-beta and -delta, but not of TCR-alpha and -gamma, genes was found to be unique for each tumor line showing T-cell clonality. Mature or truncated TCR-beta, -gamma and -delta transcripts were detected in the tumor cells, but all of them were found to be non-functional in cDNA cloning analysis. These results suggested that tumor cells from SBL are immature double-negative T-cells expressing non-functional TCR gamma delta transcripts to somewhat differentiated degrees.