Microsoft Word - AHA213BF

Dr. J. Dufer, J. Bernard, Laboratoire d’Hématologie, Institut Jean-Godinot, BP171, F-51056 Reims Cedex (France) Recently, Chilosi et al. [2] reported heterogeneous expression of the enzyme dipeptidyl-aminopepti-dase IV (DAP IV; EC 3.4.14.4.) in T-cell chronic lym-phocytic leukemia. The authors reached the conclusions that cytochemical demonstration of DAP IV correlates with the expression of the OKT4, FcμR markers, characterizing a human T-cell subpopula-tion which contains helper T lymphocytes. Furthermore, they stated that DAP IV was much more specific for T lymphocytes than other cytochemical markers such as non-specific esterase (NSE), /J-glucuronidase (BG) or acid phosphatase (AP). Using monoclonal antibodies, we obtained very similar results on peripheral blood lymphocytes from healthy donors. The identification of cell surface antigens was performed using a specific monoclonal antibody rosetting technique [1] which included an incubation of lymphoid cells with monoclonal antibodies and a subsequent treatment with ox erythro-cytes coated with affinity purified anti-mouse Ig antibody. Monoclonal antibodies used were OKT3 (Pan T-cell), OKT4 or Leu3a (Helper/inducer T cells) and OKT8 or Leu2a (Suppressor/cytotoxic T cells). The rosette suspensions obtained were cyto-centrifuged and stained for cytochemical detection of DAP IV [5], NSE, AP and BG [1]. An important point to emphasize is the ‘one step’ character of the technique used which does not require any isolation procedure of the lymphoid subsets and allows simultaneous detection of both enzyme and surface markers using conventional light microscopy. Table I. Cytochemical reactions of human peripheral blood T lymphocytes subsets Enzyme Lymphocyte subsets1 T3+ T3Leu3a+ Leu2a + AP 76 ± 2 75 ± 1 76 ± 3 77 ± 3 BG 85 ± 4 72 ± 4 82 ± 2 87 ± 3 ANAE2 64 ± 4 9 ± 3 76 ± 3 23 ± 4 DAP IV 56 ± 3 1 ± 1 83 ± 1 11 + 5 1 Results are expressed as percent of rosettes with apositive cytochemical reaction. Mean ± SEM of individual values from 5 subjects. 2 ANAE dot-like pattern of reaction only. Table I shows that, as we previously described [1], NSE activity in dot-like form is higher in helper/inducer T-cells (76% positive cells) than in suppressor/ cytotoxic T-cells (23% positive cells; p < 0.001). Nevertheless, a non-negligible fraction of T-cells described as devoid of any helper activity (T8+ cells) express this enzymatic pattern. On the other hand, the DAP IV activity