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Quantitative and qualitative studies of leukaemic cell dipeptidylpeptidases II and IV
C S Scott1, A N Stark, J Minowada
1Department of Haematology, Cookridge Hospital, Leeds, U.K.
Abstract:
Cellular concentrations of dipeptidylpeptidases (DAP) II and IV were determined by fluorimetric assay in 152 cases of leukaemia and 24 permanent T-cell lines. Whilst its estimation appears to have few diagnostic applications, it was found that DAPII levels were generally higher in prolymphocytoid CLL variants (CLL-Pro) compared with "typical" CLL cases. Qualitatively, DAPII extracted from leukaemic B- and T-cells did not differ significantly with respect to molecular weight (Mr 82 kD: FPLC gel filtration) or substrate affinity (Km). Similarly, a single molecular weight species (Mr 189 kD) of DAPIV was also detected in all leukaemic sonicates examined although, in quantitative terms, increased DAPIV levels were primarily associated with a subgroup of CD4-positive postthymic malignancies. Studies of immature T-cell proliferations however indicated that DAPIV expression was unrelated to either stage of immunological differentiation or CD4 expression. No evidence of lineage restriction was found for either enzyme and it is concluded that variations in DAP cytochemical staining patterns reflect quantitative rather than qualitative differences.
Insights
Dipeptidylpeptidases II and IV levels in leukemia cells showed variations. DAP II was higher in CLL-Pro variants, while DAP IV increased in CD4-positive malignancies, suggesting quantitative differences.
Area of Science:
- Biochemistry
- Hematology
- Immunology
Background:
- Dipeptidylpeptidases (DAP) II and IV are enzymes with roles in cellular processes.
- Leukemia involves abnormal proliferation of blood cells, and enzyme expression can be altered.
Purpose of the Study:
- To determine cellular concentrations of DAP II and IV in leukemia and T-cell lines.
- To investigate potential diagnostic applications and correlations with specific leukemia subtypes.
Main Methods:
- Fluorimetric assay was used to quantify DAP II and IV.
- 152 leukemia cases and 24 T-cell lines were analyzed.
- Fast Protein Liquid Chromatography (FPLC) gel filtration was used to assess molecular weight.
Main Results:
- DAP II levels were generally higher in prolymphocytoid chronic lymphocytic leukemia (CLL-Pro) compared to typical CLL.
- DAP II from leukaemic cells showed consistent molecular weight and substrate affinity.
- Increased DAP IV levels were associated with CD4-positive postthymic malignancies.
- DAP IV expression in immature T-cells was independent of differentiation stage or CD4 expression.
Conclusions:
- Variations in DAP II and IV levels in leukemia appear to be quantitative rather than qualitative.
- DAP cytochemical staining patterns likely reflect these quantitative differences.
- No evidence of lineage restriction was found for either enzyme.