Production of B‐cell growth factor interleukin 2 and gamma interferon by peripheral blood lymphocytes from patients with chronic lymphocytic leukemia of B‐cell type

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Abstract
Chronic lymphocytic leukemia of B‐cell type (B‐CLL) is a malignant disease characterized by monoclonal proliferation of small lymphocytes of B‐cell origin, usually associated with suppression of polyclonal B‐cell activation (i.e., proliferation and differentiation). Normal human B‐cell proliferation is controlled by different T‐cell‐derived lymphokines, including interleukin 2 (IL2) and gamma interferon (γ‐IFN), that account for the majority of the B‐cell growth factor (BCGF) activity produced by mitogen‐activated peripheral blood mononuclear cells (PBMCs). We have previously shown an increased and dysregulated secretion of IL2 in peripheral blood from patients with BCLL. BCGF, IL2, and γ‐IFN productions by phytohemagglutinin (PHA)‐stimulated PBMCs were investigated in 13 patients with active untreated B‐CLL and 11 healthy donors. BCLL PBMCs produced a significant amount of BCGF (6 U/ml) despite the low percentage of T cells (10%) associated with this disease as compared with that found in healthy donors (61%). BCGF production in normal controls and B‐CLL patients was tripled after irradiation of PBMCs or addition of indomethacin. γ‐IFN secretion in B‐CLL patients was decreased when compared with normal controls. Therefore, when γ‐IFN was calculated per fixed number of T cells, production was significantly higher in B‐CLL patients than in normal controls, showing a dilution of the productive cells. This study suggests that T cells from B‐CLL patients are functional in terms of BCGF production despite their decreased percentage and abnormalities in surface markers.