Dipeptidyl peptidase IV activity in cells of T-lymphoid origin is decreased in cultures with 12-0-tetradecanoylphorbol-13-acetate (TPA).

Dipeptidyl peptidase IV (DPP IV) is a specific enzyme for cells of T-lymphocytic lineage. It has been attempted to induce DPP IV activity in DPP IV negative T-lymphoid leukaemias by 12-o-tetradecanoylphrobol-13-acetate (TPA). Isolated cells from peripheral blood of 6 healthy blood donors and 22 patients with various types of leukaemia were cultivated in RPMI-1640 medium with 20% fetal calf serum alone (control) or supplemented with 20% human placenta conditioned medium (HPCM) or with 16 nmol/l TPA for 3 days. The percentage of DPP IV positive lymphocytes from blood donors remained unchanged in control and HPCM cultures, but decreased significantly in TPA cultures. Leukemic cells from three DPP IV positive cases of acute T-lymphoblastic leukaemia (T-ALL) reacted to the TPA treatment in a similar manner. Leukaemic cells of two DPP IV negative T-ALL cases remained negative in all three types of cultures, thus no induction of DPP IV activity was found. Other normal blood cells as well as leukaemic cells of 7 null-ALL, 1 preB-ALL, 3 B-CLL and 6 AML patients were DPP IV negative before and after cultivation in all types of culture. These findings showed that DPP IV is specifically expressed in cells of T-lymphocytic lineage even after short-term cultivation. HPCM was found to have no effect on DPP IV activity in T-lymphoid cells.