title: Dipeptidylaminopeptidase IV activity in normal and leukemic T-cell subpopulations.
abstract: Dipeptidylaminopeptidase IV (DAP IV) cytochemical reactivity was investigated in monoclonal antibody defined T-lymphocyte subpopulations from normal blood and in cells from a series of T-cell leukemias of defined immunologic phenotype. A combined monoclonal antibody/immunocolloidal gold technic, which enabled simultaneous visualisation of immunogold label and DAP IV reactivity, was used to study enzyme reactivity in normal T-cell subpopulations. Single or several discrete granules of DAP IV reaction product were observed in 72% of OKT3+ and OKT4+ cells, whereas a significantly (P less than 0.01) lower percentage of OKT8+ cells (41%) displayed positivity; B-cells were invariably DAP IV negative. In the T-cell leukemias, DAP IV reactivity was strongest in T-lymphoblastic lymphoma and T-prolymphocytic leukemia cells. In contrast, DAP IV activity was absent or expressed in a minority of cells of the more immature T-acute lymphoblastic leukemia. The enzyme reaction also was negative in lymphocytes from other mature T-cell leukemias: T-chronic lymphocytic leukemia (OKT8+), adult T-cell lymphoma-leukemia, and Sezary syndrome (both OKT4+). DAP IV expression did not parallel that of acid phosphatase or alpha-naphthyl acetate esterase in leukemic T-lymphoid cells except in T-lymphoblastic lymphoma and T-prolymphocytic leukemia, where a strong reaction with the three hydrolytic enzymes was observed.
mesh_terms: D000911:Antibodies, Monoclonal; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000097:blood*; D010450:Endopeptidases / Q000097:blood*; D006046:Gold / Q000378:metabolism; D006801:Humans; D007938:Leukemia / Q000097:blood* / Q000201:enzymology; D009283:Naphthol AS D Esterase / Q000097:blood; D013601:T-Lymphocytes / Q000145:classification / Q000201:enzymology*
chemical_list: D000911:Antibodies, Monoclonal; D006046:Gold; D009283:Naphthol AS D Esterase; D010450:Endopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases