Possible prognostic significance of the assessment of dipeptidylpeptidase II in peripheral blood lymphocytes of patients with chronic lymphocytic leukemia.
In 115 patients with chronic lymphocytic leukemia (CLL), grouped according to the staging system as proposed by Rai et al., dipeptidylpeptidase II (DPP II) reaction was carried out in smears of peripheral blood using Lys-Pro-MNA and Lys-Ala-MNA as substrates and Fast Blue B (FBB) as the coupling agent in cacodylate buffer, pH 5.5. In patients with stable disease a significantly lower number of DPP II positive lymphocytes was found. On the other hand, a high number of DPP II positive lymphocytes indicated a progressive disease. Lys-Ala-MNA proved to be a better substrate for these purposes. When comparing these results with the stage of the disease proposed by Rai et al., a good correlation was found for Stages 0, I and II. However, in the Stages III, and particularly in the Stage IV, there was a wide range of DPP II values, although the average value calculated from the data of all patients of this group was high. Patients with low DPP II values had usually a stable disease in spite of thrombocytopenia which precluded them from allocation to Stage IV. It is concluded that the assessment of the number of DPP II positive lymphocytes represents a simple and reliable prognostic criteria in patients with B type CLL.