Immunophenotypic characteristics of T-acute lymphoblastic leukemia cells in relation to DPP IV enzyme expression.

In the present study we have examined immunophenotypic characteristics ofT-acute lymphoblastic leukemia (T-ALL) cells in relation to the expression of enzyme dipeptidyl peptidase IV (DPP IV). Peripheral blood and bone marrow cells of T-ALL patients at diagnosis were estimated. Cell surface markers were detected by a standard immunofluorescence assay and FACStar flow cytometry using a broad panel of monoclonal antibodies to define T-cell immunophenotype. DPP IV activity was investigated in phenotypically defined T-lymphoblasts. Association between DPP IV expression and proliferation was monitored by the expression of CD71 and CD38, which could be considered as markers of activation and proliferation, and by the silver-staining of nucleolar organizer regions-related proteins (argyrophilic proteins). Lymphoblasts, divided according to the presence or absence of DPP IV activity revealed remarkable heterogeneity in the immunophenotypic features. The vast majority of DPP IV positive T-ALL cases expressed CD4, CD8, CD7, CD5, CD2 along with CD71 and CD38 antigens, but the cells were surface membrane CD3 antigen negative. The phenotype of DPP IV negative cases displayed membrane CD3 antigen and variable expression of CD4 and CD8. CD71 and CD38 were frequently negative. It appears, that DPP IV active cells form the population with immature phenotype, as evidenced by mCD3 antigen absence. Relation between DPP IV positive cells and proliferation activity of T-blasts was observed, given by the presence of CD71 and CD38 positivity and overexpression of argyrophilic proteins (AgNORs). In conclusion, our study indicates a close relationship between DPP IV activity and the features ofT-cell immaturity. Association among DPP IV, CD71, CD38 and AgNORs might reflect possible relationship between immature phenotype and proliferative ability of blast cells in T-ALL patients.