Eleni Thanopoulou

Impaired generation of bone marrow CD34‐derived dendritic cells with low peripheral blood subsets in patients with myelodysplastic syndrome

Myelodysplastic syndrome (MDS) is a stem cell disorder characterized by ineffective haematopoiesis and blood cytopenias. The present study investigated the potential of bone marrow CD34+ progenitors in MDS patients to proliferate and differentiate into dendritic cells (DCs) in a cytokine‐supplemented liquid culture system and analysed the status of blood DC subsets in these patients. CD34+ progenitors had low potential to generate DCs in vitro, as the number of DCs obtained from one CD34+ cell was significantly lower compared with controls (median value 0·2 vs. 4, P = 0·003). In patients, the survival and proliferation of CD34+ cells in culture was not correlated to the degree of apoptosis. Phenotypically and functionally CD34+‐derived DCs were similar in MDS patients and normal subjects. The percentage of both circulating DC subsets in patients was extremely diminished compared with controls (myeloid DC: 0·10 ± 0·10% vs. 0·35 ± 0·13%, P < 0·001; plasmacytoid DC: 0·11 ± 0·10% vs. 0·37 ± 0·14%, P < 0·001). In cases with the 5q deletion both CD34‐derived DCs and blood DCs harboured the cytogenetic abnormality. Our results indicate that, in MDS, the production of DCs is affected by the neoplastic process resulting in ineffective ‘dendritopoiesis’ with low blood DC precursor numbers. This quantitative DC defect probably contributes to the poor immune response against infectious agents and to the escape of the malignant clone from immune recognition with disease progression towards acute leukaemia.

Disease-Related Anemia in Chronic Lymphocytic Leukemia Is Not Due to Intrinsic Defects of Erythroid Precursors: A Possible Pathogenetic Role for Tumor Necrosis Factor-Alpha

Background/Aims: Disease-related anemia in chronic lymphocytic leukemia (CLL) occurs when the obvious causes are excluded while its pathogenesis is still obscure. We investigated its underlying mechanisms in 56 untreated patients with CLL. Methods: Bone marrow (BM) lymphocytic infiltration was estimated in trephine biopsies. Serum erythropoietin (EPO) and tumor necrosis factor-α (TNF-α) levels were measured by ELISA. The potential of BM CD34+ to differentiate into erythroid cells was evaluated by methylcellulose-based assays and in liquid cultures supplemented with EPO, SCF, IL-3 ± TNF-α. The response of erythroid precursors to EPO ± TNF-α was assessed by detecting activated key proteins of EPO-EPO receptor signalling pathway using Western Blot and EMSA. Results: Bone marrow lymphocytic infiltration was not exclusively responsible for disease-related anemia and CD34+ cells were intrinsically capable of generating erythroid precursors. Also, no deficiency of serum erythropoietin (EPO) or defective intracellular response of erythroid precursors to EPO ± TNF-α stimulation was observed. Serum TNF-α levels were found increased in anemic CLL patients and TNF-α appeared to directly inhibit the erythroid development in early stages of erythropoiesis. Conclusion: We concluded that CLL-related anemia was not due to intrinsic defects of erythroid precursors, but might result from the direct suppressive effect of TNF-α on the erythroid production.