Terminal deoxynucleotidyl transferase (TdT) in RadLV-induced C57BL thymomas

Newborn C57BL mice exposed to RadLV at birth were followed and periodically sampled for thymus and bone marrow TdT activity. Tumors detected at or before 100 days had mostly low TdT levels. Large thymic lymphocytic tumors detected after 100 days had elevated total TdT content per gland. Serial samples showed a changing TdT pattern with time. The mid period shifted from low levels to normal-to-high levels for both TdT content and total TdT per gland. No unusual bone marrow TdT activity change preceded the appearance of thymomas. TdT marks a unique precursor cell highly sensitive to RadLV associated with lymphomagenesis. RadLV induced both TdT+ and TdT- thymic lymphomas and both types were found to occur after lymphoma initiation by injection of RadLV into newborns.