Establishment in culture and characterization of a strain with mast cell and monocytic properties from the bone marrow of a child with diffuse cutaneous mastocytosis

Abstract Bone marrow was isolated from a child with congenital mastocytosis. Upon prolonged in vitro culture, initially in the presence of interleukin-3 (IL-3), a population of relatively large fusiform, strongly adherent cells grew out plus a subpopulation of smaller nonadherent cells. The morphology of the adherent cells was not typical of fibroblasts, epithelial cells, nor of standard hematopoietic cell types, whereas the morphology of the nonadherent cells resembled mast cells. Neither cell type required the presence of IL-3 nor a feeder layer of fibroblasts for continued growth. Attempts to isolate the two populations were unsuccessful. This cell strain comprised of both cell populations has been termed human bone marrow-derived mastocytosis cells (HBM-M). These cells were found to possess some of the cytochemical, ultrastructural, and surface phenotypic features of degranulated mast cells. They reacted with the mast cell marker, monoclonal antibody YB5.B8, but not with the basophil specific monoclonal antibody Bsp-1 and released the inflammatory mediators histamine, leukotriene C4, prostaglandin D2, and platelet-activating factor constitutively. This release was not potentiated by immunologic- or nonimmunologic-activating stimuli. In addition, they exhibited cytochemical and surface phenotypic features of monocytes. Our results indicate that a population of abnormal proliferative cells exist in the marrow of this patient; that these cells may be responsible for the patient's pronounced systemic proliferation of mast cells and the associated symptoms; and that the cell's mast cell, monocyte properties may be indicative of a common bone marrow-derived mast cell/monocyte precursor.

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Establishment in culture and characterization of a strain with mast cell and monocytic properties from the bone marrow of a child with diffuse cutaneous mastocytosis

Blood ◽

10.1182/blood.v78.2.290.bloodjournal782290 ◽

1991 ◽

Vol 78 (2) ◽

pp. 290-303

Author(s):

SA Krilis ◽

SG Warneford ◽

J Macpherson ◽

S Kyradji ◽

L Dalla-Pozza ◽

...

Keyword(s):

Monoclonal Antibody ◽

Bone Marrow ◽

Mast Cell ◽

Mast Cells ◽

Platelet Activating Factor ◽

Prostaglandin D2 ◽

Adherent Cells ◽

Phenotypic Features ◽

Nonadherent Cells

Bone marrow was isolated from a child with congenital mastocytosis. Upon prolonged in vitro culture, initially in the presence of interleukin-3 (IL-3), a population of relatively large fusiform, strongly adherent cells grew out plus a subpopulation of smaller nonadherent cells. The morphology of the adherent cells was not typical of fibroblasts, epithelial cells, nor of standard hematopoietic cell types, whereas the morphology of the nonadherent cells resembled mast cells. Neither cell type required the presence of IL-3 nor a feeder layer of fibroblasts for continued growth. Attempts to isolate the two populations were unsuccessful. This cell strain comprised of both cell populations has been termed human bone marrow-derived mastocytosis cells (HBM-M). These cells were found to possess some of the cytochemical, ultrastructural, and surface phenotypic features of degranulated mast cells. They reacted with the mast cell marker, monoclonal antibody YB5.B8, but not with the basophil specific monoclonal antibody Bsp-1 and released the inflammatory mediators histamine, leukotriene C4, prostaglandin D2, and platelet-activating factor constitutively. This release was not potentiated by immunologic- or nonimmunologic-activating stimuli. In addition, they exhibited cytochemical and surface phenotypic features of monocytes. Our results indicate that a population of abnormal proliferative cells exist in the marrow of this patient; that these cells may be responsible for the patient's pronounced systemic proliferation of mast cells and the associated symptoms; and that the cell's mast cell, monocyte properties may be indicative of a common bone marrow-derived mast cell/monocyte precursor.

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Thrombopoietin Regulates Proliferation and Maturation of Murine Mast Cells.

Blood ◽

10.1182/blood.v104.11.1707.1707 ◽

2004 ◽

Vol 104 (11) ◽

pp. 1707-1707

Author(s):

Giovanni Migliaccio ◽

Barbara Ghinassi ◽

Lucia Centurione ◽

Maria Zingariello ◽

Lucia Bianchi ◽

...

Keyword(s):

Bone Marrow ◽

Mast Cell ◽

Cell Differentiation ◽

Growth Factor ◽

Mast Cells ◽

Wild Type ◽

Connective Tissues ◽

Immature Cells

Abstract Megakaryocytopoiesis is regulated by extrinsic (interaction of the growth factor thrombopoietin, TPO with its receptor Mpl) and intrinsic (interaction between the trascription factors GATA-1 and Fog-1) factors. The observation that mice impaired for GATA-1 expression (i.e. harbouring the GATA-1low mutation) are defective not only in megakaryocyte maturation but also in mast cell differentiation (Migliaccio et al. J Exp Med197:281, 2003), led us to investigate whether TPO might control mast cell differentiation as well. We first observed that mice genetically unable to responde to TPO (Mplnull mice) express in the connective tissues 5 times more mast cells than their normal littermates. Then, we analysed the effects on mast cell differentiation of in vivo treatment with TPO. Normal mice, and their GATA-1low littermates, were injected i.p. with TPO (100 μg/kg/day per 5 days, kindly provided by Kirin Brewery, Japan) and the number of immature (Toluidinepos) and mature (AlcianBlue/Saphraninepos) mast cells present in the connective tissues of the animals, as well as the frequency of GATA-1pos and TUNELpos mast cells, was evaluated 14 days after treatment. In wild-type animals, TPO reduced the presence of GATA-1 in mast cells (by immuno-histochemistry) and increased the number of immature cells (from 320±28 to 852±60) and of those undergoing apoptosis (from 16±1 to 600±43). In contrast, in GATA-1low animals, TPO-treatment induced the expression of GATA-1 in mast cells while decreased the number of immature cells (from 1100±72 to 427±29) as well as that of apoptotic cells (from 600±45 to 60±2). The role of TPO on mast cell differentiation were further confirmed by the analysis of the effects exerted by the growth factor on in vitro differentiation of bone marrow derived mast cells (BMMC). In these experiments, wild type bone marrow and spleen cells were cultured for 21 days with SCF and IL-3 with or without TPO and BMMC differentiation measured on the basis of the number of cells expressing the phenotype c-kithigh/CD34high and FcεRIpos. In cultures stimulated with SCF and IL-3, all the cells expressed the phenotype c-kithigh/CD34high and FcεRIpos. In contrast, in cultures supplemented also with SCF, IL-3 and TPO, only 25% of the cells were c-kithigh/CD34high and none of them was FcεRIpos. These results establish a role for TPO in the control of mast cell differentiation (possibly by modulating the GATA-1 content of the cells) and unveil further similarities between the mechanism(s) controlling megakaryocyte and mast cell differentiation.

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AK002, a Novel Humanized Monoclonal Antibody to Siglec-8, Inhibits Mast Cell Activity and Depletes Eosinophils in Ex Vivo Bone Marrow Tissue from Patients with Systemic Mastocytosis

Blood ◽

10.1182/blood-2018-99-119232 ◽

2018 ◽

Vol 132 (Supplement 1) ◽

pp. 1104-1104 ◽

Cited By ~ 1

Author(s):

Bradford A Youngblood ◽

Emily C Brock ◽

John Leung ◽

Alan T Chang ◽

Christopher Bebbington ◽

...

Keyword(s):

Monoclonal Antibody ◽

Bone Marrow ◽

Flow Cytometry ◽

Mast Cell ◽

Mast Cells ◽

Ex Vivo ◽

Systemic Mastocytosis ◽

Cell Activity ◽

Receptor Expression ◽

Long Term Treatment

Abstract INTRODUCTION: Systemic Mastocytosis (SM) is a rare disease characterized by the clonal proliferation and accumulation of mast cells in the bone marrow, respiratory and gastrointestinal tracts, and organs such as the skin, liver, spleen, and brain. Common symptoms include pruritus, flushing, headache, cognitive impairment, fatigue, diarrhea, abdominal pain, hypotension and skin lesions, as well as an increased risk for osteoporosis and anaphylaxis. SM is currently managed with antihistamines, cromolyn sodium, and leukotriene blocking agents, which lack specificity and efficacy. In addition, glucocorticoids can provide temporary relief in some cases; however long-term treatment with steroids is not appropriate due to their many side effects. Siglec-8 is an inhibitory receptor selectively expressed on human mast cells and eosinophils, and therefore represents a novel target for the treatment of SM. Antibodies to Siglec-8 have been shown to inhibit mast cell activity and induce apoptosis of eosinophils. AK002 is a novel, humanized, non-fucosylated IgG1 monoclonal antibody to Siglec-8. This study evaluates the expression of Siglec-8 and ex vivo activity of AK002 on mast cells and eosinophils in bone marrow biopsies from patients with SM. METHODS: Bone marrow aspirates were obtained from patients clinically diagnosed with SM and processed to remove red blood cells. Multi-color flow cytometry was used to quantify eosinophils and mast cells and to evaluate the activation state of mast cells. The ex vivo activity of AK002 against eosinophils and mast cells was evaluated by flow cytometry. The inhibitory activity of AK002 agaist mast cells was also examined by quantifying cytokine levels in cultured bone marrow aspirate supernatants. RESULTS: All mast cells and eosinophils in bone marrow aspirates from SM patients displayed high Siglec-8 receptor expression (Figure 1). These mast cells also expressed the SM specific markers, CD25 (Figure 1) and CD30 and increased levels of cell surface degranulation markers. The expression of CD25 on mast cells significantly decreased following overnight treatment with AK002. AK002 also significantly reduced the level of mast cell-associated cytokines produced in cultured bone marrow supernatants, including IL-6, IL-8, and TNFα (Figure 2A). These changes in mast cell activity after AK002 treatment were not due to a reduction in mast cell numbers. In contrast, overnight incubation of AK002 significantly reduced the number of bone marrow eosinophils compared to an isotype control (Figure 2B). CONCLUSIONS: Bone marrow aspirates from patients with SM had activated mast cells and eosinophils that displayed robust expression of Siglec-8. AK002 demonstrated SM mast cell inhibition in ex vivo bone marrow aspirates. AK002 also had depleting effects on eosinophils, which may be valuable to SM patients with associated eosinophilia. These encouraging results could represent a novel approach for the treatment of SM. Disclosures Youngblood: Allakos, Inc.: Employment. Brock:Allakos, Inc.: Employment. Leung:Allakos, Inc.: Employment. Chang:Allakos, Inc.: Employment. Bebbington:Allakos, Inc.: Employment. Tomasevic:Allakos, Inc.: Employment.

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Notch Signaling-Dependant Expulsion of Parasites through Mast Cell-Mediated Immunity.

Blood ◽

10.1182/blood.v104.11.1473.1473 ◽

2004 ◽

Vol 104 (11) ◽

pp. 1473-1473

Author(s):

Mamiko Sakata-Yanagimoto ◽

Etsuko Yamaguchi-Nakagami ◽

Toru Sakai ◽

Keiki Kumano ◽

Atsushi Kunisato ◽

...

Keyword(s):

Bone Marrow ◽

Mast Cell ◽

Mast Cells ◽

Notch Signaling ◽

Cell Generation ◽

Pre Treatment ◽

And Function ◽

Tgf Β1

Abstract [Background] Notch signaling is known to be important in hematopoiesis, but very little information is available about its significance in mast cells. Here we provide direct evidence that notch signaling is critical for both development and function of mast cells in vitro and in vivo. [Methods] A Lin− fraction of mouse bone marrow cells was cultured on immobilized Delta1 in the presence of SCF and IL-3, and emerging Lin−FcεRI+c-Kit+ mast cells were characterized. Next, production of mouse mast cell protease-1 (mMCP-1), which is specific for nematode infection through locally expressed TGF-β1 in vivo, by bone marrow-derived mast cells (BMMC) was analyzed after the stimulation with Delta1 in the presence of TGF-β1. Finally, mice were infected with Strongyloides venezuelensis after pre-treatment with Delta1, and expulsion of the worms was examined. [Results] Lin−FcεRI+c-Kit+ mast cells developed remarkably earlier if stimulated with Delta1 (at one week, 15% vs. 3%). DAPT, a γ-secretase inhibitor, blocked the Delta1 effect, while it did not affect the regular time-course mast cell generation by SCF and IL-3. SB431542, a selective inhibitor of TGF-β1 signaling, also blocked early mast cell generation by Delta1. Delta1 augmented mMCP-1 expression and secretion from BMMC by 50 fold. Both DAPT and SB431542 showed a dose-dependent inhibition of Delta1 effect on mMCP-1 expression and secretion. Pre-treatment of the hosts with Delta1 promoted the expulsion of S. venezuelensis, (left/inoculated ratios of worms, 3% vs. 40%) while Delta1 had no effect in the mast cell-deficient W/Wv mice. [Discussion] Our observations reveal that notch signaling regulates both development and function of mast cells in vitro in conjunction with TGF-β1 signaling. In vivo, it is also likely that Delta1 facilitates the functional maturation of intestinal mast cells to eradicate parasites. More precise mechanism of Delta1 action on mast cells in vivo is under a study.

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Phenotypic changes of bone marrow-derived mast cells after intraperitoneal transfer into W/Wv mice that are genetically deficient in mast cells.

Journal of Experimental Medicine ◽

10.1084/jem.165.3.615 ◽

1987 ◽

Vol 165 (3) ◽

pp. 615-627 ◽

Cited By ~ 63

Author(s):

K Otsu ◽

T Nakano ◽

Y Kanakura ◽

H Asai ◽

H R Katz ◽

...

Keyword(s):

Bone Marrow ◽

Mast Cell ◽

Mast Cells ◽

Adoptive Transfer ◽

Gel Filtration ◽

Chondroitinase Abc ◽

Indirect Immunofluorescence Staining ◽

Deficient Mice

The ability of mouse IL-3-dependent, bone marrow culture-derived mast cells (BMMC) to generate serosal mast cells (SMC) in vivo after adoptive transfer to mast cell-deficient mice has been defined by chemical and immunochemical criteria. BMMC differentiated and grown from WBB6F1-+/+ mouse progenitor cells in medium containing PWM/splenocyte-conditioned medium synthesized a approximately 350,000 Mr protease-resistant proteoglycan bearing approximately 55,000 Mr glycosaminoglycans, as defined by gel filtration of each. Approximately 85% of the glycosaminoglycans bound to the cell-associated BMMC proteoglycans were chondroitin sulfates based upon their susceptibility to chondroitinase ABC digestion; HPLC of the chondroitinase ABC-generated unsaturated disaccharides revealed these glycosaminoglycans to be chondroitin sulfate E. As determined by heparinase and nitrous acid degradations, approximately 10% of the glycosaminoglycans bound to BMMC proteoglycans were heparin. In contrast, mast cells recovered from the peritoneal cavity of congenitally mast cell-deficient WBB6F1-W/Wv mice 15 wk after intraperitoneal injection of BMMC synthesized approximately 650,000 Mr protease-resistant proteoglycans that contained approximately 80% heparin glycosaminoglycans of approximately 105,000 Mr. Thus, after adoptive transfer, the SMC of the previously mast cell-deficient mice were like those recovered from the normal WBB6F1-+/+ mice that were shown to synthesize approximately 600,000 Mr proteoglycans that contained approximately 80% heparin glycosaminoglycans of approximately 115,000 Mr. As assessed by indirect immunofluorescence staining and flow cytometry using the B1.1 rat mAb (an antibody that recognizes an epitope located on the neutral glycosphingolipid globopentaosylceramide), approximately 5% of BMMC bound the antibody detectably, whereas approximately 72% of the SMC that were harvested from mast cell-deficient mice 15 wk after adoptive transfer of BMMC were B1.1-positive; approximately 82% of SMC from WBB6F1-+/+ mice bound the antibody. These biochemical and immunochemical data are consistent with the results of previous adoptive transfer studies that characterized mast cells primarily on the basis of morphologic and histochemical criteria. Thus, IL-3-dependent BMMC developed in vitro, cells that resemble mucosal mast cells, can give rise in vivo to SMC that express phenotypic characteristics of connective tissue mast cells.

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In vivo exit of c-kit+/CD49dhi/β7+ mucosal mast cell precursors from the bone marrow following infection with the intestinal nematode Trichinella spiralis

Blood ◽

10.1182/blood-2003-09-3146 ◽

2004 ◽

Vol 103 (7) ◽

pp. 2655-2660 ◽

Cited By ~ 35

Author(s):

Joanne L. Pennock ◽

Richard K. Grencis

Keyword(s):

Bone Marrow ◽

Mast Cell ◽

Mast Cells ◽

Trichinella Spiralis ◽

Mucosal Mast Cell ◽

Hematopoietic Tissue ◽

In Vivo Experiments ◽

Intestinal Nematode

Abstract We have used the parasite helminth Trichinella spiralis to study the generation and differentiation of mast cell progenitors in the bone marrow of mice, as this infection triggers an intestinal mastocytosis which correlates with parasite expulsion. C-kit+ mast cell progenitors have previously been defined by methylcellulose colony-forming units and by limiting dilution assays in vitro. In vivo experiments have demonstrated the essential requirement by mast cells for specific integrin expression. We have defined 2 c-kit+ populations in the bone marrow, one of which coexpresses CD49d/β7 integrin, a marker essential for small intestine immigration. We have confirmed the phenotype of these cells by using antagonistic anti-c-kit antibody in vivo. Our data show that the loss of c-kit+/β7+ cells from the bone marrow correlates with their appearance in the blood and precedes detection of mature mast cells in the gut by 3 days. This exit correlates with an increase in soluble stem cell factor (SCF) in the serum, suggesting that the c-kit/SCF interaction may be chemotactic or haptotactic in nature. This study shows that during infection the bone marrow environment generates mast cells destined for the intestinal mucosa before their exit into the periphery, indicating a clear interplay between infection site and hematopoietic tissue. (Blood. 2004;103:2655-2660)

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Identification of Progenitors Committed to Basophil and/or Mast Cell Lineages.

Blood ◽

10.1182/blood.v104.11.779.779 ◽

2004 ◽

Vol 104 (11) ◽

pp. 779-779

Author(s):

Yojiro Arinobu ◽

Hiromi Iwasaki ◽

Michael F. Gurish ◽

Shi-ichi Mizuno ◽

Hirokazu Shigematsu ◽

...

Keyword(s):

Bone Marrow ◽

Mast Cell ◽

Mast Cells ◽

Bone Marrow Cells ◽

Innate Immune Responses ◽

Developmental Relationships ◽

Cell Lineages ◽

Cd34 Cells ◽

High Level

Abstract Eosinophils, basophils and mast cells are multifunctional hematopoietic effectors that co-operate to mount a variety of allergic and innate immune responses. Their origin and developmental relationships, however, have not yet been resolved, and remain as one of the major issues in the biology of hematopoiesis. Here we report that progenitors bipotent for basophils and mast cells (basophil/mast cell progenitors: BMCPs) are prospectively isolatable downstream of granulocyte/monocyte progenitors (GMPs). Since both basophils and mast cells express the αβγ2 form of FcεRI on their surface, we hypothesized that early progenitors restricted to these lineages may have already upregulated these molecules. Thus, FcεRIα-expressing cells were searched within the Lin−CD34+ bone marrow and spleen cells. Lin−CD34+ bone marrow cells contained a small fraction of cells expressing a high level of FcεRIα that were all c-Kit−. Purified Lin−CD34+FcεRIαhic-Kit− cells were cultured, and they gave rise exclusively to pure basophil colonies, which were named as basophil progenitors (BaPs). In contrast, the spleen had a small fraction of Lin−CD34+ cells expressing a low level of FcεRIα and a high level of c-Kit. Strikingly, single Lin−CD34+FcεRIαloc-Kithi cells formed colonies containing both basophils and mast cells as well as pure mast cell or basophil colonies. This indicates that at least a fraction of Lin−CD34+FcεRIαloc-Kithi cells are bipotent for basophils and mast cells. We thus named the Lin−CD34+FcεRIαloc-Kithi cells as BMCPs. Identification of BMCPs formally proves for the first time that basophils and mast cells share a common progenitor stage. After 3-day culture, BMCPs gave rise to Lin−CD34+FcεRIαhic-Kit−BaPs and Lin−CD34+FcεRIαhic-Kit+ cells which exclusively formed pure mast cell colonies. Lin−CD34+FcεRIαhic-Kit+ cells were named as mast cell progenitors (MCPs). All of these progenitors are located downstream of GMPs since GMPs gave rise to BMCPs, BaPs and MCPs in vitro after 3-day culture with SCF, IL-3, and IL-9. The intestine is known to collect mast cell colony-forming activity. Since MCPs were not isolatable as a distinct population in the bone marrow or the spleen, we searched for MCPs in the intestine by using similar markers. We newly identified Lin−CD34+FcεRIαloc-Kitlo cells in the intestine, and these cells exclusively formed pure mast cell colonies. In mice sensitized with OVA to induce allergic reaction, BMCPs, BaPs and intestinal MCPs expanded by1.5- to 5-fold in number after OVA administration. This strongly suggests that these populations constitute critical stages in physiological pathways for each lineage development. Taken together, it is likely that the initial commitment into basophil/mast cell lineages occurs in the spleen, and that spleen BMCPs may migrate into the bone marrow to become BaPs or into the intestine to become MCPs. These progenitor populations should be useful to analyze the mechanism of commitment into each of these lineages, and could also be therapeutic targets for a variety of allergic and autoimmune disorders.

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Mouse bone marrow-derived mast cells (mBMMC) obtained in vitro from mice that are mast cell-deficient in vivo express the same panel of granule proteases as mBMMC and serosal mast cells from their normal littermates.

Journal of Experimental Medicine ◽

10.1084/jem.180.1.67 ◽

1994 ◽

Vol 180 (1) ◽

pp. 67-73 ◽

Cited By ~ 26

Author(s):

K K Eklund ◽

N Ghildyal ◽

K F Austen ◽

D S Friend ◽

V Schiller ◽

...

Keyword(s):

Bone Marrow ◽

Mast Cell ◽

Steady State ◽

Mast Cells ◽

Induced Expression ◽

Mast Cell Protease ◽

Steady State Levels ◽

Mouse Mast Cell

The ear, skin, and purified serosal mast cells of WBB6F1/J-(+/+) (WB-(+/+)) and WCB6F1/J-(+/+) (WC-(+/+)) mice contain high steady-state levels of the transcripts that encode mouse mast cell protease (mMCP) 2, mMCP-4, mMCP-5, mMCP-6, and mouse mast cell carboxypeptidase A (mMC-CPA). In contrast, no mast cell protease transcripts are present in abundance in the ear and skin of WBB6F1/J-W/Wv (W/Wv) and WCB6F1/J-Sl/Sld (Sl/Sld) mice which are mast cell-deficient in vivo due to defects in their c-kit and c-kit ligand genes, respectively. We now report that the immature bone marrow-derived mast cells (mBMMC) obtained in vitro with recombinant interleukin 3 (rIL-3) or WEHI-3 cell conditioned medium from WB-(+/+), WC-(+/+), W/Wv, and Sl/Sld mice all contain high steady-state levels of the mMCP-2, mMCP-4, mMCP-5, mMCP-6, and mMC-CPA transcripts. As assessed immunohistochemically, mMCP-2 protein and mMCP-5 protein are also present in the granules of mBMMC from WB-(+/+), WC-(+/+), and W/Wv mice. That Sl/Sld and W/Wv mBMMC contain high steady-state levels of five granule protease transcripts expressed by the mature serosal, ear, and skin mast cells of their normal +/+ littermates suggests that c-kit-mediated signal transduction is not essential for inducing transcription of these protease genes. Because rIL-4 inhibits the rIL-10-induced expression of mMCP-1 and mMCP-2 in BALB/cJ mBMMC, the ability of rIL-4 to influence protease mRNA levels in WC-(+/+) mBMMC and W/Wv mBMMC was investigated. Although rIL-10 induced expression of the mMCP-1 transcript in WC-(+/+) and W/Wv mBMMC, rIL-4 was not able to suppress the steady-state levels of the mMCP-1 transcript or any other protease transcript in these cultured mast cells. Thus, not only do BALB/cJ mBMMC express fewer granule proteases than mBMMC from mast cell-deficient strains and their normal littermates but the subsequent induction of late-expressed proteases in BALB/cJ mBMMC is more tightly regulated by IL-3 and IL-4.

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bcr-abl-Induced cell lines can switch from mast cell to erythroid or myeloid differentiation in vitro

Blood ◽

10.1182/blood.v79.5.1271.bloodjournal7951271 ◽

1992 ◽

Vol 79 (5) ◽

pp. 1271-1281 ◽

Cited By ~ 1

Author(s):

AG Elefanty ◽

S Cory

Keyword(s):

Bone Marrow ◽

Mast Cell ◽

Mast Cells ◽

Cell Lines ◽

Bone Marrow Cells ◽

Hematopoietic Growth Factors ◽

Autocrine Loop ◽

Hematopoietic Disorders ◽

Marrow Cells

The chimeric bcr-abl gene formed by the Philadelphia translocation is thought to initiate chronic myeloid leukemia. Engraftment of mice with bone marrow cells infected with a bcr-abl retrovirus has been shown to elicit multiple hematopoietic disorders, including a clonal but nontransplantable hyperproliferation of erythroid and/or mast cells. Culture of spleen and bone marrow cells from such mice usually yielded mast cell lines, even when erythroid disease dominated the primary animal. The mast cells, which carried the same proviral insert as the primary disease, generally grew slowly and were neither transplantable nor clonogenic in agar until they had been cultured for several months. Unexpectedly, several bcr-abl-induced lines switched in vitro from mast cell to megakaryocytic and/or erythroid character, and one became myeloid. The dramatic phenotypic shifts seem likely to involve changes occurring within progenitor cells maintaining the clone, rather than mutation of mature mast cells. The variant lines exhibited substantial spontaneous differentiation, despite being readily transplantable and therefore fully transformed. The production of hematopoietic growth factors by the mast cell lines and their phenotypic variants may implicate an autocrine loop in their evolution. These novel bcr-abl cell lines should aid in the study of genetic events in the progression from chronic to acute leukemia and facilitate analysis of hematopoietic lineage commitment.

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