Analysis of ex vivo Apoptosis of B and T cells from Peripheral Blood and Bone Marrow of Patients with Chronic Lymphocytic Leukemia

Abstract

In this study we analyzed selected parameters of apoptosis in leukemic cells from peripheral blood and bone marrow of patients with chronic lymphocytic leukemia (CLL). The percentage of apoptotic leukemic B cells (Δψm^low/CD19⁺) was significantly lower in peripheral blood (median: 0.99%) than in bone marrow (median: 1.41%) (p<0.0001). These data can support the idea that these two compartments might have different proliferative statuses. There was an inverse correlation between the ex vivo percentage of apoptotic cells and lymphocytosis (R=-0.34; p<0.01), and a direct correlation between the percentage of PB apoptotic B cells and the Rai stage (R=0.42; p<0.05). The percentage of Δψm^low/CD19⁺ cells was significantly higher in ZAP-70-positive patients than from ZAP-70-negative patients (p<0.01). There was also a significant difference in the median percentage of apoptotic leukemic B cells between the patients carrying del(11q22.3) or/and del(17p13.1) (2.7%) and the patients without these unfavorable genetic aberrations (1.6%) (p<0.01). The B cells from ZAP-70-positive patients with more aggressive disease seem to be more susceptible to spontaneous apoptosis than those from ZAP-70-negative patients. We conclude that the evaluation of ex vivo apoptosis might provide new important information concerning the biology and prognosis of CLL.