Megakaryocyte Colony Formation Research Articles

Megakaryocyte and erythroid colony formation in essential thrombocythaemia and reactive thrombocytosis: diagnostic value and correlation to complications.

Megakaryocyte and erythroid colony formation in vitro by progenitors from the bone marrow and/or blood was studied in 61 patients with essential thrombocythaemia (ET) and 22 patients with reactive thrombocytosis (RT) using the methyl cellulose assay. 47 (77%) of the patients with ET showed megakaryocyte and/or erythroid spontaneous colony formation while 14 (23%) patients did not have any kind of spontaneous colonies. Spontaneous megakaryocyte colony formation was seen in 42 (69%) of the patients and 36 (59%) ET patients showed spontaneous erythroid growth. 31 patients had both types of spontaneous colonies. 11 patients showed only spontaneous megakaryocyte colony formation, and five patients only spontaneous erythroid growth. None of the patients with RT or of the normal controls showed either type of spontaneous growth. Neither the presence of spontaneous megakaryocyte colony formation nor the number of spontaneous colonies correlated with the platelet count. Patients with spontaneous megakaryocyte growth had significantly more often thromboembolic or haemorrhagic problems than those without spontaneous colony formation. In conclusion, it was found that a great majority of patients with ET but none of those with RT grow spontaneous megakaryocyte and/or erythroid colonies. Spontaneous colony formation is strong evidence for a myeloproliferative disorder. The presence of spontaneous colony growth is associated with an increased risk of thromboembolic or haemorrhagic complications regardless of the platelet count, particularly among young patients.

Human Interleukin-4 Inhibits Proliferation of Megakaryocyte Progenitor Cells in Culture

We studied the effects of recombinant human interleukin-4 (rhIL-4) on megakaryocyte colony formation from enriched hematopoietic progenitors. IL-4 strongly inhibited pure and mixed megakaryocyte colony formation in a dose-dependent manner. Formation of erythroid bursts, eosinophil colonies, and erythrocyte-containing mixed colonies was not affected by the addition of IL-4 as reported previously (Sonoda Y, et al; Blood 75:1615, 1990). Delayed addition experiments suggested that IL-4 acts on an early stage of proliferation of megakaryocyte progenitors. Neutralizing antibodies (antisera) prepared against transforming growth factor beta, tumor necrosis factor alpha, interferon alpha (IFN alpha), and IFN gamma did not affect the inhibitory effects of IL-4 on pure and mixed megakaryocyte colony formation. In addition, the inhibitory effects of IL-4 was also seen in serum-free cultures and in cultures containing highly enriched CD34+, HLA-DR+ cells as a target population. These results indicate that IL-4 may function as one of the negative regulators in human megakaryocytopoiesis in vitro.

Human interleukin-4 inhibits proliferation of megakaryocyte progenitor cells in culture

We studied the effects of recombinant human interleukin-4 (rhIL-4) on megakaryocyte colony formation from enriched hematopoietic progenitors. IL-4 strongly inhibited pure and mixed megakaryocyte colony formation in a dose-dependent manner. Formation of erythroid bursts, eosinophil colonies, and erythrocyte-containing mixed colonies was not affected by the addition of IL-4 as reported previously (Sonoda Y, et al; Blood 75:1615, 1990). Delayed addition experiments suggested that IL-4 acts on an early stage of proliferation of megakaryocyte progenitors. Neutralizing antibodies (antisera) prepared against transforming growth factor beta, tumor necrosis factor alpha, interferon alpha (IFN alpha), and IFN gamma did not affect the inhibitory effects of IL-4 on pure and mixed megakaryocyte colony formation. In addition, the inhibitory effects of IL-4 was also seen in serum-free cultures and in cultures containing highly enriched CD34+, HLA-DR+ cells as a target population. These results indicate that IL-4 may function as one of the negative regulators in human megakaryocytopoiesis in vitro.

Synergism between serum factor(s) and erythropoietin in inducing murine megakaryocyte colony formation: the synergistic factor in serum is distinct from interleukin-11 and stem cell factor (c-kit ligand) [letter

Synergism between serum factor(s) and erythropoietin in inducing murine megakaryocyte colony formation: the synergistic factor in serum is distinct from interleukin-11 and stem cell factor (c-kit ligand) [letter

A novel megakaryocyte potentiator produced by MC-1 human lung cancer cell line.

The hematopoietic stimulating activity of a human lung cancer cell line, MC-1, was investigated. The protein fraction (MC-1 protein) was prepared from the serum-free culture supernatant of MC-1 cells using hydroxyapatite and concanavalin A-agarose columns. In serum-containing cultures, MC-1 protein stimulated colony formation by megakaryocyte colony-forming units (CFU), erythroid burst-forming units and granulocyte/macrophage (GM) CFU. The stimulating effect was strongest for megakaryocyte CFU. The factor having megakaryocyte colony-stimulating activity was shown to be a protein whose molecular weight was determined to be 23,000 daltons by gel filtration. By various analyses, this protein was shown to be molecularly different from the heretofore-identified cytokines that may affect megakaryocytopoiesis, i.e., interleukin-1 (IL-1), IL-2, IL-3, IL-6, IL-7, IL-11, granulocyte colony-stimulating factor (CSF), macrophage CSF, GM-CSF, leukemia inhibitory factor, stem cell factor and tumor necrosis factor. Under serum-free conditions, MC-1 protein augmented murine megakaryocyte colony formation in the presence of murine IL-3 and increased the acetylcholinesterase activity of purified murine megakaryocytes. It was also shown that MC-1 protein stimulated human megakaryocyte colony formation. It was concluded that MC-1 cells produce a megakaryocyte potentiator which is molecularly different from any heretofore-identified cytokines.

Megakaryocyte, erythroid and granulocyte-macrophage colony formation in myelodysplastic syndromes.

Bone marrow progenitor cell assays of three cell lineages, i.e., colony-forming unit megakaryocytes (CFU-Meg), burst-forming unit erythrocytes (BFU-E) and colony-forming unit granulocyte-macrophages (CFU-GM), were performed for 21 patients with myelodysplastic syndromes (MDS). Markedly reduced or absent colony formation was found in 67% of the patients for CFU-Meg and all patients except 2 with refractory anemia (RA) for BFU-E. Abnormal CFU-GM colony formation was found in only 5 of 12 patients with RA and RA with ring sideroblasts, in contrast to all of the RA patients with excess of blasts and excess of blasts in transformation. Defective colony formation of all three cell lineages was seen in 63% of the MDS patients. The colony number of CFU-Meg correlated significantly with the numbers of both BFU-E and CFU-GM. These findings indicate that hematopoiesis in MDS patients is disturbed due to a qualitative or quantitative defect at the multipotent stem cell level.

Interaction of fibroblast growth factor (FGF) with megakaryocytopoiesis and demonstration of FGF receptor expression in megakaryocytes and megakaryocytic-like cells

We have investigated the interaction of fibroblast growth factor (FGF) with megakaryocytopoiesis. Acidic FGF (aFGF) stimulated the proliferation of murine megakaryocytes and human erythroleukemia (HEL) cells in a concentration-dependent manner. The concentrations of aFGF required to elicit half-maximum and maximum effects were similar for HEL and megakaryocytic colony formation. The effect of aFGF was comparable to that of basic FGF (bFGF) in both cell types. The effect of both FGFs was found to be synergistic with interleukin-3 (IL-3), and was abrogated by a monoclonal anti-IL-6 antibody. A specific cell surface receptor complex of approximately 120 Kd was detected for FGF by crosslinking experiments on HEL cells and total bone marrow (BM) cells. Single-cell autoradiography of megakaryocytes in BM smears and BM cultures showed binding sites for 125I-aFGF. Northern blot analysis of messenger RNA (mRNA) from total BM and HEL cells showed a 4.4-kb mRNA specific for FGF receptors type 1 (flg) and type 2 (bek). This was confirmed by polymerase chain reaction, which also showed the presence of FGF receptor mRNA in megakaryocytic-like cells, normal megakaryocytes, and platelets. Together, these results indicate that FGF is involved in megakaryocytopoiesis and suggest that this interaction may be mediated via FGF receptor type 1 and type 2 located on the megakaryocytic lineage or on accessory cells responsible for the release of megakaryocytic growth-promoting activities.

Interaction of Fibroblast Growth Factor (FGF) With Megakaryocytopoiesis and Demonstration of FGF Receptor Expression in Megakaryocytes and Megakaryocytic-Like Cells

AbstractWe have investigated the interaction of fibroblast growth factor (FGF) with megakaryocytopoiesis. Acidic FGF (aFGF) stimulated the proliferation of murine megakaryocytes and human erythroleukemia (HEL) cells in a concentration-dependent manner. The concentrations of aFGF required to elicit half-maximum and maximum effects were similar for HEL and megakaryocytic colony formation. The effect of aFGF was comparable to that of basic FGF (bFGF) in both cell types. The effect of both FGFs was found to be synergistic with interleukin-3 (IL-3), and was abrogated by a monoclonal anti–IL-6 antibody. A specific cell surface receptor complex of ~120 Kd was detected for FGF by cross-linking experiments on HEL cells and total bone marrow (BM) cells. Single-cell autoradiography of megakaryocytes in BM smears and BM cultures showed binding sites for 125I-aFGF. Northern blot analysis of messenger RNA (mRNA) from total BM and HEL cells showed a 4.4-kb mRNA specific for FGF receptors type 1 (flg) and type 2 (bek). This was confirmed by polymerase chain reaction, which also showed the presence of FGF receptor mRNA in megakaryocytic-like cells, normal megakaryocytes, and platelets. Together, these results indicate that FGF is involved in megakaryocytopoiesis and suggest that this interaction may be mediated via FGF receptor type 1 and type 2 located on the megakaryocytic lineage or on accessory cells responsible for the release of megakaryocytic growth-promoting activities.

Interactions between recombinant human erythropoietin and serum factor(s) on murine megakaryocyte colony formation

We investigated the interactions between human erythropoietin (hEpo) and serum factor(s) on murine megakaryocyte (MK) colony formation. Serum-free cultures supported the growth of a large number of murine MK colonies in the presence of murine interleukin-3 (mIL-3). The addition of fetal calf serum (FCS) to mIL-3-containing cultures resulted in only a minimal increase in the number of murine MK colonies. In contrast, hEpo alone had no murine MK colony-stimulating activities in serum-free cultures. hEpo required the presence of FCS, murine serum, or human serum in cultures to promote murine MK colony growth and synergized with these sera to stimulate murine MK colony formation. Furthermore, sera from patients with aplastic anemia showed higher synergistic activities with hEpo than sera from hematologically normal persons (normal human serum). When normal human serum was fractionated by gel- filtration chromatography, two peaks with the synergistic activity were observed in the eluent. However, serum did not show any synergistic effects with hEpo on the growth of murine GM colonies or murine colony- forming unit-erythroid-derived colonies. Although human serum synergized with hEpo to stimulate murine MK colony formation, human cytokines such as IL-3, IL-4, IL-6, granulocyte-macrophage colony- stimulating factor (GM-CSF) and granulocyte-CSF (G-CSF) failed to induce murine MK colony formation in Epo-containing cultures. In cultures containing human IL-1 alpha + human IL-6 + hEpo as well as in cultures containing hEpo, human IL-3 and human GM-CSF failed to show stimulatory effects on murine MK colony formation. Moreover, the synergistic activity of human serum with hEpo could not be neutralized by antibodies such as antihuman IL-1 alpha, antihuman IL-3, antihuman IL-4, antihuman IL-6, antihuman G-CSF, and antihuman GM-CSF. Our data show that serum contains a growth factor(s) that synergizes with Epo to stimulate the proliferation and differentiation of MK precursors, and strongly suggest that this factor(s) is an unique growth factor(s) that is distinct from IL-1 alpha, IL-3, IL-4, IL-6, G-CSF, and GM-CSF.

Interactions Between Recombinant Human Erythropoietin and Serum Factor(s) on Murine Megakaryocyte Colony Formation

We investigated the interactions between human erythropoietin (hEpo) and serum factor(s) on murine megakaryocyte (MK) colony formation. Serum-free cultures supported the growth of a large number of murine MK colonies in the presence of murine interleukin-3 (mIL-3). The addition of fetal calf serum (FCS) to mIL-3-containing cultures resulted in only a minimal increase in the number of murine MK colonies. In contrast, hEpo alone had no murine MK colony-stimulating activities in serum-free cultures. hEpo required the presence of FCS, murine serum, or human serum in cultures to promote murine MK colony growth and synergized with these sera to stimulate murine MK colony formation. Furthermore, sera from patients with aplastic anemia showed higher synergistic activities with hEpo than sera from hematologically normal persons (normal human serum). When normal human serum was fractionated by gel-filtration chromatography, two peaks with the synergistic activity were observed in the eluent. However, serum did not show any synergistic effects with hEpo on the growth of murine GM colonies or murine colony-forming unit-erythroid-derived colonies. Although human serum synergized with hEpo to stimulate murine MK colony formation, human cytokines such as IL-3, IL-4, IL-6, granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte-CSF (G-CSF) failed to induce murine MK colony formation in Epo-containing cultures. In cultures containing human IL-1 alpha + human IL-6 + hEpo as well as in cultures containing hEpo, human IL-3 and human GM-CSF failed to show stimulatory effects on murine MK colony formation. Moreover, the synergistic activity of human serum with hEpo could not be neutralized by antibodies such as antihuman IL-1 alpha, antihuman IL-3, antihuman IL-4, antihuman IL-6, antihuman G-CSF, and antihuman GM-CSF. Our data show that serum contains a growth factor(s) that synergizes with Epo to stimulate the proliferation and differentiation of MK precursors, and strongly suggest that this factor(s) is an unique growth factor(s) that is distinct from IL-1 alpha, IL-3, IL-4, IL-6, G-CSF, and GM-CSF.

Impaired in vitro growth of purified (CD34+) hematopoietic progenitors in human immunodeficiency virus-1 seropositive thrombocytopenic individuals

In this report the role played by human immunodeficiency virus type-1 (HIV-1) in the pathogenesis of HIV-1-related thrombocytopenia was investigated. CD34+ hematopoietic stem/progenitor cells were purified from the bone marrow (BM) of HIV-1(+) thrombocytopenic patients, HIV- 1(+) nonthrombocytopenic individuals, HIV-1(-) patients with immune thrombocytopenic purpura, and HIV-1(-) normal donors. CD34+ cells from HIV-1(+) thrombocytopenic individuals alone showed a reduced capacity to give rise to megakaryocytic colonies (CFU-Meg) and also a progressive and significant decline in cell number when placed in liquid culture containing recombinant human interleukin-3 (rIL-3). This decline involved not only megakaryocyte but also erythroid and granulocyte/macrophage progenitors. The defects in megakaryocyte colony formation and CD34+ cell growth did not result from a productive HIV-1 infection of CD34+ cells. Moreover, HIV-1 DNA was absent from CD34+ cells in 10 of 12 thrombocytopenic patients examined. On the other hand, the decreased survival/proliferation of CD34+ cells in liquid culture, within the HIV-1(+) thrombocytopenic patients, was correlated with the presence of HIV-1 p24 antigen in BM plasma. These results demonstrate an impairment of CD34+ cells in HIV-1(+) individuals presenting thrombocytopenia as the only hematologic manifestation. Furthermore, these findings suggest that increased viral replication in the BM microenvironment may cause this impairment and possibly contributes to HIV-induced thrombocytopenia.

Impaired In Vitro Growth of Purified (CD34+) Hematopoietic Progenitors in Human Immunodeficiency Virus-1 Seropositive Thrombocytopenic Individuals

In this report the role played by human immunodeficiency virus type-1 (HIV-1) in the pathogenesis of HIV-1-related thrombocytopenia was investigated. CD34+ hematopoietic stem/progenitor cells were purified from the bone marrow (BM) of HIV-1(+) thrombocytopenic patients, HIV-1(+) nonthrombocytopenic individuals, HIV-1(-) patients with immune thrombocytopenic purpura, and HIV-1(-) normal donors. CD34+ cells from HIV-1(+) thrombocytopenic individuals alone showed a reduced capacity to give rise to megakaryocytic colonies (CFU-Meg) and also a progressive and significant decline in cell number when placed in liquid culture containing recombinant human interleukin-3 (rIL-3). This decline involved not only megakaryocyte but also erythroid and granulocyte/macrophage progenitors. The defects in megakaryocyte colony formation and CD34+ cell growth did not result from a productive HIV-1 infection of CD34+ cells. Moreover, HIV-1 DNA was absent from CD34+ cells in 10 of 12 thrombocytopenic patients examined. On the other hand, the decreased survival/proliferation of CD34+ cells in liquid culture, within the HIV-1(+) thrombocytopenic patients, was correlated with the presence of HIV-1 p24 antigen in BM plasma. These results demonstrate an impairment of CD34+ cells in HIV-1(+) individuals presenting thrombocytopenia as the only hematologic manifestation. Furthermore, these findings suggest that increased viral replication in the BM microenvironment may cause this impairment and possibly contributes to HIV-induced thrombocytopenia.

Suppressive effect of LD78 on the proliferation of human hemopoietic progenitors.

LD78 is a cDNA newly isolated front human stimulated tonsillar lymphocytes. The expression of LD78 is related to inflammatory responses and its structure has a homology with macrophage inflammatory protein 1‐α, which is known to have an inhibitory effect on murine CFU‐S. Using a colony assay technique, we examined the effects of LD78 on human hemopoietic progenitors. The addition of doses of 100 ng/ml or more of LD78 suppressed the colony formation of KMT‐2, a factor‐dependent myelomonocytic cell line established from cord blood cells; this suppressive activity was neutralized by the addition of antibody against LD78. The same doses of LD78 suppressed the formation of neutrophil, macrophage, and megakaryocytic colonies which were supported by human interleukin3 and erythropoietin; however, LD78 did not affect colony formation by either non‐phagocytic mono‐nuclear cells or sorted CD34+ cells. The conditioned medium of KMT‐2 cells or peripheral blood mononuclear cells cultured with LD78 suppressed colony formation by CD34+ cells. From these findings, it is suggested that LD78 affects phagocytic cells and induces factors that are inhibitory for hemopoiesis. We consider LD78 to be a new cytokine that plays an inhibitory role in hemopoiesis.

New insights into the regulation of megakaryocytopoiesis by haematopoietic and fibroblastic growth factors and transforming growth factor beta 1.

Effects of cytokines on murine megakaryocyte (MK) colony formation from either unfractionated marrow cells or purified early haematopoietic cells were studied. Recombinant interleukin-3 (IL3), interleukin-6 (IL6), granulocyte-macrophage colony-stimulating factor (GM-CSF), erythropoietin (Epo) and acidic and basic fibroblast growth factor (aFGF and bFGF) each was able to stimulate MK colony growth although they varied somewhat in their potential. IL6 and FGFs, in addition to their effect on MK colony growth, increased the size of individual MK. The combination of IL3 with IL6 or FGF resulted in an additive action. Monoclonal anti-IL6 antibody completely neutralized the activity of mouse IL6 and FGFs but had no effect on human IL6, mouse IL3 and GM-CSF. When using purified lineage negative marrow cells, only IL3 and IL6 promoted MK colony formation. Transforming growth factor beta 1 (TGF-beta 1) at 10-200 pg/ml selectively inhibited IL3-induced MK colony formation, and at 0.2-0.5 ng/ml it still had no obvious effect on the activity of IL6 or GM-CSF but caused an inhibition of FGF-induced MK colony formation. These data suggest that differential mechanisms are involved in the regulation of megakaryocytopoiesis by IL3, IL6, FGFs and GM-CSF, and that TGF-beta 1 negatively regulates MK development mainly by interfering with the action of IL3.

Role of the KIT protooncogene in normal and malignant human hematopoiesis.

The role of the KIT protooncogene in human hematopoiesis is uncertain. Therefore, we examined KIT mRNA expression in normal human bone marrow mononuclear cells (MNC) and used antisense oligodeoxynucleotides (oligomers) to disrupt KIT function. KIT mRNA was detected with certainty only in growth factor-stimulated MNC. Expression was essentially abrogated by making MNC quiescent or by inhibiting myb gene function. Oligomers blocked KIT mRNA expression in a dose-response and sequence-specific manner, thereby allowing functional examination of the KIT receptor. In experiments with either partially purified or CD34(+)-enriched MNC, neither granulocyte nor megakaryocyte colony formation was inhibited by oligomer exposure. In contrast, KIT antisense oligomers inhibited interleukin 3/erythropoietin-driven erythroid colony formation approximately 70% and "stem cell factor"/erythropoietin-driven colony formation 100%. The presence of erythroid progenitor cell subsets with differential requirements for KIT function is therefore suggested. Growth of hematopoietic colonies from chronic myeloid leukemia and polycythemia vera patients was also inhibited, while acute leukemia colony growth appeared less sensitive to KIT deprivation. These results suggest that KIT plays a predominant role in normal erythropoiesis but may be important in regulating some types of malignant hematopoietic cell growth as well. They also suggest that KIT expression is linked to cell metabolic activity and that its expression may be regulated by or coregulated with MYB.

Growth factor-dependent inhibition of normal hematopoiesis by N-ras antisense oligodeoxynucleotides.

To determine whether N-ras expression is required at specific stages of the process of in vitro normal human hematopoiesis, adherent- and T lymphocyte-depleted mononuclear marrow cells (A-T-MNC) or highly purified progenitors (CD34+ cells) were cultured in semisolid medium, under conditions that favor the growth of specific progenitor cell types, after exposure to N-ras sense and antisense oligodeoxynucleotides. N-ras antisense, but not sense, oligodeoxynucleotide treatment of A-T-MNC and CD34+ cells resulted in a significantly decreased number of granulocyte/macrophage colony-forming units (CFU-GM) induced by interleukin 3 (IL-3) or granulocyte/macrophage colony-stimulating factor (GM-CSF) and of macrophage colonies (CFU-M) induced by M-CSF, but not of granulocytic colonies induced with G-CSF or IL-5. However, the same treatment significantly inhibited colony formation induced by each of the above factors in combination with IL-3. Megakaryocytic colony (CFU-Meg) formation from A-T-MNC or CD34+ cells in the presence of IL-6 + IL-3 + erythropoietin (Epo) was also markedly decreased after antisense oligodeoxynucleotide treatment. Erythroid colonies derived from A-T-MNC in the presence of Epo (CFU-E) were not inhibited upon antisense treatment, whereas those arising from A-T-MNC or CD34+ cells in the presence of IL-3 + Epo (BFU-E) were markedly affected. These results are consistent with the hypothesis that distinct signal transduction pathways, involving N-ras or not, are activated by different growth factors in different hematopoietic progenitor cells.

Effects of the Stem Cell Factor, c-kitLigand, on Human Megakaryocytic Cells

The kit ligand (KL), also termed stem cell factor (SCF), is a recently discovered hematopoietic growth factor that augments response of early progenitor cells to other growth factors and supports proliferation of continuous mast cell lines. Histological studies suggest that the receptor for SCF/KL, the c-kit proto-oncogene product, is present in bone marrow megakaryocytes. We studied the effects of SCF/KL on immortalized human megakaryocytic cell lines (CMK, CMK6, and CMK11-5) and on isolated human marrow megakaryocytes. Human SCF/KL alone or in combination with the hematopoietic growth factors, interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL-6, stimulated proliferation of these megakaryocytic cell lines. SCF/KL treatment did not alter expression of gpIb, gpIIb/IIIa, LFA-1, ICAM-1, or GMP-140 in CMK cells. No effect on ploidy was observed. Furthermore, human SCF/KL induced expression of IL-1 alpha, IL-1 beta, IL-2, and IL-6 in CMK cells. In a fibrin clot system, SCF/KL modestly potentiated megakaryocyte colony formation when added alone to cultures containing CD34+, DR+ bone marrow cells. Addition of SCF/KL with IL-3 or GM-CSF to these cultures resulted in a more marked marrow megakaryocytic cells. SCF/KL may directly affect megakaryocytopoiesis, as well as secondarily modulate hematopoiesis through induction of cytokines in target cells.

Effects of the stem cell factor, c-kit ligand, on human megakaryocytic cells

The kit ligand (KL), also termed stem cell factor (SCF), is a recently discovered hematopoietic growth factor that augments response of early progenitor cells to other growth factors and supports proliferation of continuous mast cell lines. Histological studies suggest that the receptor for SCF/KL, the c-kit proto-oncogene product, is present in bone marrow megakaryocytes. We studied the effects of SCF/KL on immortalized human megakaryocytic cell lines (CMK, CMK6, and CMK11–5) and on isolated human marrow megakaryocytes. Human SCF/KL alone or in combination with the hematopoietic growth factors, interleukin-3 (IL- 3), granulocyte-macrophage colony-stimulating factor (GM-CSF), and IL- 6, stimulated proliferation of these megakaryocytic cell lines. SCF/KL treatment did not alter expression of gpIb, gpIIb/IIIa, LFA-1, ICAM-1, or GMP-140 in CMK cells. No effect on ploidy was observed. Furthermore, human SCF/KL induced expression of IL-1 alpha, IL-1 beta, IL-2, and IL- 6 in CMK cells. In a fibrin clot system, SCF/KL modestly potentiated megakaryocyte colony formation when added alone to cultures containing CD34+, DR+ bone marrow cells. Addition of SCF/KL with IL-3 or GM-CSF to these cultures resulted in a more marked marrow megakaryocytic cells. SCF/KL may directly affect megakaryocytopoiesis, as well as secondarily modulate hematopoiesis through induction of cytokines in target cells.

Interleukin-11: A novel stroma-derived cytokine

Interleukin-11 (IL-11) is a novel stroma-derived cytokine that acts on both hematopoietic progenitors and stromal cells. IL-11 was originally identified in a medium conditioned by the macaque bone marrow-derived stromal cell line PU-34 and cloned as a growth factor for the IL-6-dependent plasmacytoma cell line T1165. IL-11 stimulates T-cell dependent development of antibody-producing B cells and is synergistic with IL-3 to stimulate megakaryocyte colony formation. Adipogenesis inhibitory factor (AGIF) was cloned from the human bone marrow-derived stromal cell line KM-102. The AGIF cDNA sequence was revealed to be identical to that of the IL-11 cDNA. AGIF inhibits the process of adipogenesis of the bone marrow-derived preadipocyte cell line H-1 A . Other biological activities such as stimulation of stem-cell proliferation, erythropoiesis, lymphohematopoiesis and hepatic acute-phase response are also summarized. The human IL-11 gene consists of five exons and four introns, and was mapped on chromosome 19 at band 19q13.3-q13.4. A single class of high-affinity IL-11 receptor (IL-11R) of 151 kDa is present on 3T3-L1 preadipocytes. A protein-tyrosine kinase pathway may be involved in the initiation of the IL-11R-mediated signal transduction.

In vitro megakaryocyte colony formation in patients with idiopathic thrombocytopenic purpura: differences between acute and chronic ITP.

In vitro megakaryocyte colony formation from the bone marrow of patients with acute idiopathic thrombocytopenic purpura (ITP) or chronic ITP was compared using a plasma clot system. The number of megakaryocyte colony-forming units (CFU-Meg) was significantly higher (p less than 0.05) in acute ITP compared to chronic ITP (54.3 +/- 68.4 vs. 12.9 +/- 15.3/10(5) nonadherent mononuclear cells, mean +/- SD), and significantly lower (p less than 0.05) in chronic ITP compared to controls (12.9 +/- 15.3 vs. 22.8 +/- 15.9). A significant correlation was observed between platelet recovery 7 and 30 days after culture, and the number of CFU-Meg (r = 0.49 and 0.45, respectively, p less than 0.05). An inverse correlation was observed between platelet count at the time of culture and the number of Megs per colony (r = -0.48, p less than 0.05). These results indicated a difference between acute and chronic ITP in the ability to promote in vitro Meg colony formation and may suppose a different immune mechanism for thrombocytopenia in these two disorders.