title: Dipeptidylaminopeptidase IV (DAP IV) activity in normal and malignant T-cell subsets as defined by monoclonal antibodies.
abstract: The activity of dipeptidylaminopeptidase IV (DAP IV) was investigated by a cytochemical method in isolated fractions of normal peripheral blood mononuclear cells and malignant cells from 9 patients with chronic T-cell leukaemia. A positive DAP IV reaction was observed in 52% of normal T cells, a consistent negative reaction in normal B cells and monocytes. 2 distinct T-cell subsets, helper/inducer cells (T4+/T8-) and cytotoxic/suppressor cells (T4-/T8+), were negatively selected by complement-mediated cytolysis utilizing the monoclonal antibodies OKT4 and OKT8. On examination of these T-cell subsets a positive DAP IV reaction was restricted to the majority of normal T4+/T8- cells. The malignant cells from 3 patients with T-chronic lymphocytic leukaemia, expressing the cytotoxic/suppressor phenotype (T4-/T8+) lacked DAP IV activities. In contrast, almost all leukaemic cells from 3 other cases, expressing the helper/inducer phenotype (T4+/T8-), were strongly positive. Despite their T4+/T8- phenotype, the malignant cells from 3 patients with Sézary syndrome were completely DAP IV negative. These findings suggest that the DAP IV reaction may be helpful in the further characterization of normal and malignant T-cell subsets.
mesh_terms: D000368:Aged; D000911:Antibodies, Monoclonal / Q000276:immunology*; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000097:blood*; D010450:Endopeptidases / Q000097:blood*; D005260:Female; D006801:Humans; D007938:Leukemia / Q000097:blood / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D012751:Sezary Syndrome / Q000201:enzymology; D013194:Staining and Labeling; D013601:T-Lymphocytes / Q000145:classification / Q000201:enzymology*; D006377:T-Lymphocytes, Helper-Inducer / Q000201:enzymology
chemical_list: D000911:Antibodies, Monoclonal; D010450:Endopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases