High terminal deoxynucleotidyl transferase activity in a new T-cell line (RPMI 8402) of acute lymphoblastic leukemia origin.

High activity of terminal deoxynucleotidyl transferase (terminal transferase) was found in a new "thymus-dependent" cell line (RPMI 8402) which is of acute lymphoblastic leukemia origin. This enzyme resembled the terminal transferase from other human cells in all its properties including Km (0.7 x 10(-6) m for dGTP). The high activity of this enzyme in RPMI 8402 and fresh acute leukemia lymphoblasts, in contrast to the low activity of this enzyme reported for "thymus-independent' cells, suggested that this cell line may have originated from leukemia cells. Moreover, the high activity of terminal transferase in RPMI 8402 cells should make feasible large-scale purification of this enzyme for detailed studies.