THYMIC TARGETS FOR ABELSON MURINE LEUKEMIA-VIRUS ARE EARLY GAMMA/DELTA LYMPHOCYTES-T

Molecular analysis has shown that the majority of Abelson murine leukemia virus (Ab-MuLV)-induced primary thymomas represent transformed gamma/delta-thymocytes. Many of these thymomas are of monoclonal origin as judged by provirus integration pattern and contain rearranged genes encoding T-cell receptor (TCR) gamma and delta-chains but germ-line immunoglobulin heavy-chain genes. Some of the monoclonal tumors contain multiple rearranged alleles encoding TCR gamma, delta, and beta-chains. Further, one Ab-MuLV thymoma cell line contained germ-line-configuration TCR gamma- and delta-chain genes, which became rearranged after in vitro propagation. Clones of this cell line were observed to rearrange these genes after intrathymic passage. Also, some subclones of this cell line underwent rearrangement of their immunoglobulin heavy-chain genes in culture. These observations suggest that the thymic targets for Ab-MuLV transformation are early gamma/delta-thymocytes, some of which continue to rearrange their TCR gamma- and delta-chain genes.