The present study focused on whether it is possible to expand monocytic cells from CD34+ progenitor cells by using macrophage colony-stimulating factor (M-CSF) in the absence and presence of mast cell growth factor (MGF) and IL-6. It was demonstrated that CD34+ cells differentiate without expansion to functional mature monocytic cells in the presence of M-CSF or combinations of M-CSF plus IL-6 and MGF. A different response pattern was observed for the number of clonogenic cells. The addition of IL-6 or both IL-6 and MGF to M-CSF containing cultures resulted in significant higher numbers of colony-forming unit-macrophage (CFU-M) as tested in clonogenic and 3H-thymidine assays. Furthermore, M-CSF plus both IL-6 and MGF appeared to be the most potent combination to preserve the monocytic precursor in cell suspension culture assays. These results indicate that IL-6 and MGF in conjunction with M-CSF affect CD34+ cells especially at precursor level without distinct effect on the more mature stages. Secondly we studied whether M-CSF is only critical for the monocytic lineage or also affects dendritic cell (DC) development. Indeed, we were able to culture CD83+ DC from CD34+ progenitor cells in the presence of M-CSF in conjunction with TNF-alpha, IL-4, and MGF although their absolute number is almost threefold lower than the number of CD83+ cells yielded from GM-CSF plus TNF-alpha, IL-4, and MGF stimulated CD34+ cells.
Interleukin-4 (IL-4) modulates the survival, proliferation, and differentiation of a variety of hematopoietic cells. The effects are mediated through a single class of high-affinity receptors for IL-4. To understand the biologic effects of IL-4 on human T cells, we studied the regulation of IL-4 receptor (IL-4R) gene expression. We showed that IL-4R mRNA accumulation in human T cells is enhanced fourfold after activation of different secondary signaling pathways by concanavalin A (Con A), phorbol myristate acetate (PMA), the calcium ionophore A23187, and combinations of these factors. This could be ascribed to an increase in the IL-4R transcription rate and to stabilization of IL-4R mRNA resulting in a half-life of 80 to 90 minutes (v 35 to 40 minutes in resting T cells). IL-4 did enhance the IL-4R mRNA accumulation by a factor 10, which was caused by an increase in the IL-4R transcription rate and prolonging the half-life of IL-4R transcripts to 140 to 160 minutes. Finally, it was shown that A23187 induced IL-4R mRNA expression is a protein synthesis-dependent process. In contrast, Con A- , PMA-, Con A + PMA-, and Con A + A23187-induced expression of IL-4R mRNA is protein-synthesis independent. Cyclosporine A inhibited the A23187- and Con A + A23187-induced IL-4R mRNA accumulation, whereas Con A-, PMA-, and Con A + PMA-induced IL-4R mRNA expression was not affected by this drug. These data indicate that expression of IL-4 receptors on human T cells can be modulated by different intracellular signaling pathways at both transcriptional and posttranscriptional levels.
In refractory anemia (RA) and refractory anemia with ringed sideroblasts (RARS) a discrepancy is observed between the decreased in vitro erythroid colony formation and the normal or increased number of normoblasts in the bone marrow.
05). Most of the cases (73%) with increased ETU valuesshowed an augmented percentage of erythroblasts in the bone marrow, which was inversely related with the serum Epo levels (P Ͻ 0.05, r ؍ 0.51). However no correlation was found between the ETU values and the in vitro erythroid colony formation. Transfusion dependency was associated with normal to increased ETU levels (P Ͻ 0.05) and cytogenetic abnormalities (P Ͻ 0.05). These observations demonstrate that different patterns of defects can be observed in the erythropoiesis of RA and RARS patients whereby normal to increased ETU levels and the presence of cytogenetic abnormalities differentiate between cases of RA with ineffective erythropoiesis associated with regular transfusions and cases who are relatively transfusion independent.
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