Role of decreased production of interleukin-10 and interferon-gamma in spontaneous apoptosis of B-chronic lymphocytic leukemia lymphocytes in vitro.

Background And Aims: B-chronic lymphocytic leukemia (B-CLL) is characterized by the progressive accumulation of small B lymphocytes that do not undergo apoptosis due to an underlying defect. One potential mechanism of defective apoptosis may be irregular cytokine production. The goal of our investigation was to determine in vitro production of relevant cytokines by lymphocytes of B-CLL patients.

Methods: Thirty untreated (stage A) B-CLL patients, as well as 20 stage B and C patients and 30 healthy volunteers as a control group were examined. Interleukin-4 (IL-4), interferon-gamma (IFN-gamma), interleukin-10 (IL-10) and tumor necrosis factor-alpha (TNF-alpha) were measured by enzyme-linked immunosorbent assay (ELISA) in supernatants of lymphocyte cultures of all three investigated groups. The method applied for detecting apoptosis was fluorescence microscopic analysis using acridine orange/ethidium bromide (AO/EB) double staining.

Results: Investigation showed that in vitro lymphocyte production of IL-10 and IFN-gamma were significantly decreased in B-CLL patients, whereas there were no statistically significantly differences of IL-4 and TNF-alpha production among the tested groups. Compared with the spontaneous apoptosis observed in control subjects' lymphocytes, B-CLL lymphocytes showed increased percentages of apoptotic cells after incubation for 24h. Interestingly, increased spontaneous apoptosis of B-CLL lymphocytes was followed by decreased IL-10 and IFN-gamma production. Stage of disease did not influence B-CLL lymphocyte spontaneous apoptosis in vitro.

Conclusions: These changes in cytokine production in cultures of B-CLL lymphocytes may be one of the potential mechanisms in the pathogenesis of abnormal apoptosis.