Expression of Jak2V617F causes a polycythemia vera-like disease with associated myelofibrosis in a murine bone marrow transplant model.
An acquired somatic mutation,Jak2V617F,was recently discovered in most patients with polycythemia vera (PV),chronic idiopathic myelofibrosis (CIMF),and essential thrombocythemia (ET). To investigate the role of this mutation in vivo,we transplanted bone marrow (BM) transduced with a retrovirus expressing either Jak2 wild-type (wt) or Jak2V617F into lethally irradiated syngeneic recipient mice. Expression of Jak2V617F,but not Jak2wt,resulted in clinicopathologic features that closely resembled PV in humans. These included striking elevation in hemoglobin level/hematocrit,leukocytosis,megakaryocyte hyperplasia,extramedullary hematopoiesis resulting in splenomegaly,and reticulin fibrosis in the bone marrow. Histopathologic and flow cytometric analyses showed an increase in maturing myeloid lineage progenitors,although megakaryocytes showed decreased polyploidization and staining for acetylcholinesterase. In vitro analysis of primary cells showed constitutive activation of Stat5 and cytokine-independent growth of erythroid colony-forming unit (CFU-E) and erythropoietin hypersensitivity,and Southern blot analysis for retroviral integration indicated that the disease was oligoclonal. Furthermore,we observed strain-specific differences in phenotype,with Balb/c mice demonstrating markedly elevated leukocyte counts,splenomegaly,and reticulin fibrosis compared with C57Bl/6 mice. We conclude that Jak2V617F expression in bone marrow progenitors results in a PV-like syndrome with myelofibrosis and that there are strain-specific modifiers that may in part explain phenotypic pleiotropy of Jak2V617F-associated myeloproliferative disease in humans.
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产品类型:
产品号#:
04960
04902
04900
04961
04901
04963
04962
04970
04971
产品名:
MegaCult™-C胶原和无细胞因子培养基
胶原蛋白溶液
MegaCult™-C无细胞因子培养基
MegaCult™-C胶原和含细胞因子培养基
MegaCult™-C含细胞因子培养基
双室载玻片套件
MegaCult™-C CFU-Mk染色试剂盒
MegaCult™-C无细胞因子全套试剂盒
MegaCult™-C含细胞因子全套试剂盒
Berthier R et al. (MAR 1993)
Stem cells (Dayton,Ohio) 11 2 120--9
Serum-free medium allows the optimal growth of human megakaryocyte progenitors compared with human plasma supplemented cultures: role of TGF beta.
The growth of human megakaryocyte progenitors from human bone marrow (BM) cells was compared using a methylcellulose semisolid assay supplemented either by normal human plasma or by a serum-free medium. Far better growth of megakaryocyte colonies from CD34+ BM cells stimulated by interleukin 3 (IL-3) and interleukin 6 (IL-6) was observed in serum-free medium compared with human plasma supplemented cultures. These results were confirmed in liquid cultures using the same serum-free medium composition. The megakaryocytes were identified by using an immunocytochemical procedure after labeling with an anti-GPIIb-IIIa monoclonal antibody. High percentages (15 to 20%) of megakaryocytes were present in serum-free cultures stimulated by IL-3 alone or combined with IL-6. The absolute number of megakaryocytes in serum-free medium exceeds by 3.3 (IL-3 plus IL-6) to 4.4 (IL-3 alone) times the corresponding number of megakaryocytes observed in human plasma supplemented cultures. The optimal concentration of IL-3 alone was 5 ng/ml,and an optimal synergistic effect of IL-6 (5 ng/ml) was obtained when combined with a suboptimal dose of IL-3 (1 ng/ml). The poor growth of megakaryocyte colonies from CD34+ BM cells in human plasma suggested the presence of an inhibitory factor. When a neutralizing monoclonal antibody against transforming growth factor beta (TGF beta) is present in human plasma supplemented cultures of CD34+ BM cells,the number of megakaryocyte colonies is increased to the level observed in corresponding serum-free cultures. The high efficiency of this serum-free medium to promote the growth of human megakaryocytes will be useful to study the effects of regulators and platelet agonists acting on human megakaryocytes,without interference from factors in the serum.
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产品类型:
产品号#:
04961
04965
04962
04915
04807
04809
04906
04913
04803
04804
04905
04850
04974
04902
04960
04900
04901
04963
04970
04971
产品名:
MegaCult™-C胶原和含细胞因子培养基
MegaCult™-C CFU-Mk染色试剂盒
MegaCult-C 10% BSA, 6mL
MegaCult-C Human Serum, 6mL
Alkaline Phosphatase Substrate Tabs, pk
Biotin/Conjugate Goat Anti-Mu lgG, 125uL
MegaCult-C Evans Blue Stain, 5mL
Primary Ab, Anti-HuAnti-GPIIb/IIIa 360uL
MegaCult-C Control Antibody, 100 µL
Avidin-Alk Phosphatase Conjugate, 200 uL
MegaCult™-C含脂质培养基
MegaCult™-C胶原和含脂质培养基
胶原蛋白溶液
MegaCult™-C胶原和无细胞因子培养基
MegaCult™-C无细胞因子培养基
MegaCult™-C含细胞因子培养基
双室载玻片套件
MegaCult™-C无细胞因子全套试剂盒
MegaCult™-C含细胞因子全套试剂盒
Goossens S et al. (MAY 2011)
Blood 117 21 5620--30
The EMT regulator Zeb2/Sip1 is essential for murine embryonic hematopoietic stem/progenitor cell differentiation and mobilization.
Zeb2 (Sip1/Zfhx1b) is a member of the zinc-finger E-box-binding (ZEB) family of transcriptional repressors previously demonstrated to regulate epithelial-to-mesenchymal transition (EMT) processes during embryogenesis and tumor progression. We found high Zeb2 mRNA expression levels in HSCs and hematopoietic progenitor cells (HPCs),and examined Zeb2 function in hematopoiesis through a conditional deletion approach using the Tie2-Cre and Vav-iCre recombination mouse lines. Detailed cellular analysis demonstrated that Zeb2 is dispensable for hematopoietic cluster and HSC formation in the aorta-gonadomesonephros region of the embryo,but is essential for normal HSC/HPC differentiation. In addition,Zeb2-deficient HSCs/HPCs fail to properly colonize the fetal liver and/or bone marrow and show enhanced adhesive properties associated with increased β1 integrin and Cxcr4 expression. Moreover,deletion of Zeb2 resulted in embryonic (Tie2-Cre) and perinatal (Vav-icre) lethality due to severe cephalic hemorrhaging and decreased levels of angiopoietin-1 and,subsequently,improper pericyte coverage of the cephalic vasculature. These results reveal essential roles for Zeb2 in embryonic hematopoiesis and are suggestive of a role for Zeb2 in hematopoietic-related pathologies in the adult.
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产品类型:
产品号#:
03434
03444
04960
04902
04900
产品名:
MethoCult™ GF M3434
MethoCult™ GF M3434
MegaCult™-C胶原和无细胞因子培养基
胶原蛋白溶液
MegaCult™-C无细胞因子培养基
Dobo I et al. (JAN 2001)
The hematology journal : the official journal of the European Haematology Association / EHA 2 6 396--403
Comparison of four serum-free, cytokine-free media for analysis of endogenous erythroid colony growth in polycythemia vera and essential thrombocythemia.
INTRODUCTION: The assay of endogenous erythroid colony formation (EEC),a characteristic of polycythemia vera and essential thrombocythemia,is not standardized. In this multicentric study,we tested four semisolid,serum-free,cytokine-free media based on either methylcellulose (M1,M2) or collagen (C1,C2) commercialized for the EEC assay. MATERIALS AND METHODS: Bone marrow mononuclear cells (BMMC) from 73 individuals (62 patients with either polycythemia vera (26),essential thrombocythemia (19),secondary polyglobuly (17) or chronic myeloid leukemia (2) and 11 healthy donors) were grown in parallel in the four media without,or with 0.01 U/ml erythropoietin (EPo). RESULTS: In all four media EEC formation was specific,as it was not observed in cultures of patients with secondary polyglobuly or chronic myeloid leukemia,nor of healthy donors. Analysis of fresh or MGG-stained collagen gel cultures allowed detection of EEC formation significantly more frequently than methylcellulose-based media; addition of 0.01 U/ml of EPo had little or no effect on EEC formation. Collagen-based medium C1 gave better results than the other media tested: the 'C1' EEC assay was positive for 68.2% of polycythemia vera cultures with significantly higher median EEC numbers (6.5/10(5) BMMC for patients with one major criteria of polycythemia vera and 19 and 21/10(5) BMMC for patients with two or three major criteria,respectively). Medium C1 was also better for essential thrombocythemia cultures with 47.4% of positive results but with a low median EEC number (6.7/10(5) BMMC). When associated with the ELISA dosage of serum EPo,the 'C1' EEC assay allowed confirmation or elimination of the diagnosis of polycythemia vera for 91% (20/22) of polyglobulic patients. CONCLUSION: We propose that serum-free collagen-based culture systems be considered to standardize the EEC assay,now part of the new criteria of polycythemia vera.
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产品类型:
产品号#:
04961
04965
04962
04915
04807
04809
04906
04913
04803
04804
04905
04850
04974
04902
04960
04900
04901
04963
04970
04971
产品名:
MegaCult™-C胶原和含细胞因子培养基
MegaCult™-C CFU-Mk染色试剂盒
MegaCult-C 10% BSA, 6mL
MegaCult-C Human Serum, 6mL
Alkaline Phosphatase Substrate Tabs, pk
Biotin/Conjugate Goat Anti-Mu lgG, 125uL
MegaCult-C Evans Blue Stain, 5mL
Primary Ab, Anti-HuAnti-GPIIb/IIIa 360uL
MegaCult-C Control Antibody, 100 µL
Avidin-Alk Phosphatase Conjugate, 200 uL
MegaCult™-C含脂质培养基
MegaCult™-C胶原和含脂质培养基
胶原蛋白溶液
MegaCult™-C胶原和无细胞因子培养基
MegaCult™-C无细胞因子培养基
MegaCult™-C含细胞因子培养基
双室载玻片套件
MegaCult™-C无细胞因子全套试剂盒
MegaCult™-C含细胞因子全套试剂盒
Houwerzijl EJ et al. (JAN 2004)
Blood 103 2 500--6
Ultrastructural study shows morphologic features of apoptosis and para-apoptosis in megakaryocytes from patients with idiopathic thrombocytopenic purpura.
To investigate whether altered megakaryocyte morphology contributes to reduced platelet production in idiopathic thrombocytopenic purpura (ITP),ultrastructural analysis of megakaryocytes was performed in 11 ITP patients. Ultrastructural abnormalities compatible with (para-)apoptosis were present in 78% +/- 14% of ITP megakaryocytes,which could be reversed by in vivo treatment with prednisone and intravenous immunoglobulin. Immunohistochemistry of bone marrow biopsies of ITP patients with extensive apoptosis showed an increased number of megakaryocytes with activated caspase-3 compared with normal (28% +/- 4% versus 0%). No difference,however,was observed in the number of bone marrow megakaryocyte colony-forming units (ITP,118 +/- 93/105 bone marrow cells; versus controls,128 +/- 101/105 bone marrow cells; P =.7). To demonstrate that circulating antibodies might affect megakaryocytes,suspension cultures of CD34+ cells were performed with ITP or normal plasma. Morphology compatible with (para-)apoptosis could be induced in cultured megakaryocytes with ITP plasma (2 of 10 samples positive for antiplatelet autoantibodies). Finally,the plasma glycocalicin index,a parameter of platelet and megakaryocyte destruction,was increased in ITP (57 +/- 70 versus 0.7 +/- 0.2; P =.009) and correlated with the proportion of megakaryocytes showing (para-) apoptotic ultrastructure (P =.02; r = 0.7). In conclusion,most ITP megakaryocytes show ultrastructural features of (para-) apoptosis,probably due to action of factors present in ITP plasma.
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产品类型:
产品号#:
09600
09650
04960
04902
04900
04961
04901
04963
04962
04970
04971
产品名:
StemSpan™ SFEM
StemSpan™ SFEM
MegaCult™-C胶原和无细胞因子培养基
胶原蛋白溶液
MegaCult™-C无细胞因子培养基
MegaCult™-C胶原和含细胞因子培养基
MegaCult™-C含细胞因子培养基
双室载玻片套件
MegaCult™-C CFU-Mk染色试剂盒
MegaCult™-C无细胞因子全套试剂盒
MegaCult™-C含细胞因子全套试剂盒
Pirson L et al. (JUL 2006)
Stem cells (Dayton,Ohio) 24 7 1814--21
Despite inhibition of hematopoietic progenitor cell growth in vitro, the tyrosine kinase inhibitor imatinib does not impair engraftment of human CD133+ cells into NOD/SCIDbeta2mNull mice.
There is potential interest for combining allogeneic hematopoietic cell transplantation (HCT),and particularly allogeneic HCT with a nonmyeloablative regimen,to the tyrosine kinase inhibitor imatinib (Glivec; Novartis,Basel,Switzerland,http://www.novartis.com) in order to maximize anti-leukemic activity against Philadelphia chromosome-positive leukemias. However,because imatinib inhibits c-kit,the stem cell factor receptor,it could interfere with bone marrow engraftment. In this study,we examined the impact of imatinib on normal progenitor cell function. Imatinib decreased the colony-forming capacity of mobilized peripheral blood human CD133(+) cells but not that of long-term culture-initiating cells. Imatinib also decreased the proliferation of cytokine-stimulated CD133(+) cells but did not induce apoptosis of these cells. Expression of very late antigen (VLA)-4,VLA-5,and CXCR4 of CD133(+) cells was not modified by imatinib,but imatinib decreased the ability of CD133(+) cells to migrate. Finally,imatinib did not decrease engraftment of CD133(+) cells into irradiated nonobese diabetic/severe combined immunodeficient/beta2m(null) mice conditioned with 3 or 1 Gy total body irradiation. In summary,our results suggest that,despite inhibition of hematopoietic progenitor cell growth in vitro,imatinib does not interfere with hematopoietic stem cell engraftment.
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产品类型:
产品号#:
05150
04435
04445
04960
04902
04900
04961
04901
04963
04962
04970
04971
产品名:
MyeloCult™ H5100
MethoCult™ H4435 Enriched
MethoCult™ H4435 Enriched
MegaCult™-C胶原和无细胞因子培养基
胶原蛋白溶液
MegaCult™-C无细胞因子培养基
MegaCult™-C胶原和含细胞因子培养基
MegaCult™-C含细胞因子培养基
双室载玻片套件
MegaCult™-C CFU-Mk染色试剂盒
MegaCult™-C无细胞因子全套试剂盒
MegaCult™-C含细胞因子全套试剂盒
Tober J et al. (FEB 2007)
Blood 109 4 1433--41
The megakaryocyte lineage originates from hemangioblast precursors and is an integral component both of primitive and of definitive hematopoiesis.
In the adult,platelets are derived from unipotential megakaryocyte colony-forming cells (Meg-CFCs) that arise from bipotential megakaryocyte/erythroid progenitors (MEPs). To better define the developmental origin of the megakaryocyte lineage,several aspects of megakaryopoiesis,including progenitors,maturing megakaryocytes,and circulating platelets,were examined in the murine embryo. We found that a majority of hemangioblast precursors during early gastrulation contains megakaryocyte potential. Combining progenitor assays with immunohistochemical analysis,we identified 2 waves of MEPs in the yolk sac associated with the primitive and definitive erythroid lineages. Primitive MEPs emerge at E7.25 along with megakaryocyte and primitive erythroid progenitors,indicating that primitive hematopoiesis is bilineage in nature. Subsequently,definitive MEPs expand in the yolk sac with Meg-CFCs and definitive erythroid progenitors. The first GP1bbeta-positive cells in the conceptus were identified in the yolk sac at E9.5,while large,highly reticulated platelets were detected in the embryonic bloodstream beginning at E10.5. At this time,the number of megakaryocyte progenitors begins to decline in the yolk sac and expand in the fetal liver. We conclude that the megakaryocyte lineage initially originates from hemangioblast precursors during early gastrulation and is closely associated both with primitive and with definitive erythroid lineages in the yolk sac prior to the transition of hematopoiesis to intraembryonic sites.
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产品类型:
产品号#:
04960
04902
04900
04963
04962
04970
产品名:
MegaCult™-C胶原和无细胞因子培养基
胶原蛋白溶液
MegaCult™-C无细胞因子培养基
双室载玻片套件
MegaCult™-C CFU-Mk染色试剂盒
MegaCult™-C无细胞因子全套试剂盒
Pessina A et al. (FEB 2009)
Toxicology in vitro : an international journal published in association with BIBRA 23 1 194--200
Application of human CFU-Mk assay to predict potential thrombocytotoxicity of drugs.
Megakaryocytopoiesis gives rise to platelets by proliferation and differentiation of lineage-specific progenitors,identified in vitro as Colony Forming Unit-Megakaryocytes (CFU-Mk). The aim of this study was to refine and optimize the in vitro Standard Operating Procedure (SOP) of the CFU-Mk assay for detecting drug-induced thrombocytopenia and to prevalidate a model for predicting the acute exposure levels that cause maximum tolerated decreases in the platelets count,based on the correlation with the maximal plasma concentrations (C max) in vivo. The assay was linear under the SOP conditions,and the in vitro endpoints (percentage of colonies growing) were reproducible within and across laboratories. The protocol performance phase was carried out testing 10 drugs (selected on the base of their recognised or potential in vivo haematotoxicity,according to the literature). Results showed that a relationship can be established between the maximal concentration in plasma (C max) and the in vitro concentrations that inhibited the 10-50-90 percent of colonies growth (ICs). When C max is lower than IC10,it is possible to predict that the chemicals have no direct toxicity effect on CFU-Mk and could not induce thrombocytopenia due to bone marrow damage. When the C max is higher than IC90 and/or IC50,thrombocytopenia can occur due to direct toxicity of chemicals on CFU-Mk progenitors.
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产品类型:
产品号#:
04960
04902
04900
04963
04962
04970
产品名:
MegaCult™-C胶原和无细胞因子培养基
胶原蛋白溶液
MegaCult™-C无细胞因子培养基
双室载玻片套件
MegaCult™-C CFU-Mk染色试剂盒
MegaCult™-C无细胞因子全套试剂盒
Yasui K et al. (JAN 2003)
Stem cells (Dayton,Ohio) 21 2 143--51
Differences between peripheral blood and cord blood in the kinetics of lineage-restricted hematopoietic cells: implications for delayed platelet recovery following cord blood transplantation.
Cord blood (CB) cells are a useful source of hematopoietic cells for transplantation. The hematopoietic activities of CB cells are different from those of bone marrow and peripheral blood (PB) cells. Platelet recovery is significantly slower after transplantation with CB cells than with cells from other sources. However,the cellular mechanisms underlying these differences have not been elucidated. We compared the surface marker expression profiles of PB and CB hematopoietic cells. We focused on two surface markers of hematopoietic cell immaturity,i.e.,CD34 and AC133. In addition to differences in surface marker expression,the PB and CB cells showed nonidentical differentiation pathways from AC133(+)CD34(+) (immature) hematopoietic cells to terminally differentiated cells. The majority of the AC133(+)CD34(+) PB cells initially lost AC133 expression and eventually became AC133(-)CD34(-) cells. In contrast,the AC133(+)CD34(+) CB cells did not go through the intermediate AC133(-)CD34(+) stage and lost both markers simultaneously. Meanwhile,the vast majority of megakaryocyte progenitors were of the AC133(-)CD34(+) phenotype. We conclude that the delayed recovery of platelets after CB transplantation is due to both subpopulation distribution and the process of differentiation from AC133(+)CD34(+) cells.
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产品类型:
产品号#:
04064
04960
04902
04900
04961
04901
04963
04962
04970
04971
产品名:
MethoCult™ H4034 Optimum 入门试剂盒
MegaCult™-C胶原和无细胞因子培养基
胶原蛋白溶液
MegaCult™-C无细胞因子培养基
MegaCult™-C胶原和含细胞因子培养基
MegaCult™-C含细胞因子培养基
双室载玻片套件
MegaCult™-C CFU-Mk染色试剂盒
MegaCult™-C无细胞因子全套试剂盒
MegaCult™-C含细胞因子全套试剂盒
Xing S et al. (MAY 2008)
Blood 111 10 5109--17
Transgenic expression of JAK2V617F causes myeloproliferative disorders in mice.
The JAK2(V617F) mutation was found in most patients with myeloproliferative disorders (MPDs),including polycythemia vera,essential thrombocythemia,and primary myelofibrosis. We have generated transgenic mice expressing the mutated enzyme in the hematopoietic system driven by a vav gene promoter. The mice are viable and fertile. One line of the transgenic mice,which expressed a lower level of JAK2(V617F),showed moderate elevations of blood cell counts,whereas another line with a higher level of JAK2(V617F) expression displayed marked increases in blood counts and developed phenotypes that closely resembled human essential thrombocythemia and polycythemia vera. The latter line of mice also developed primary myelofibrosis-like symptoms as they aged. The transgenic mice showed erythroid,megakaryocytic,and granulocytic hyperplasia in the bone marrow and spleen,displayed splenomegaly,and had reduced levels of plasma erythropoietin and thrombopoietin. They possessed an increased number of hematopoietic progenitor cells in peripheral blood,spleen,and bone marrow,and these cells formed autonomous colonies in the absence of growth factors and cytokines. The data show that JAK2(V617F) can cause MPDs in mice. Our study thus provides a mouse model to study the pathologic role of JAK2(V617F) and to develop treatment for MPDs.
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产品类型:
产品号#:
03231
03434
03444
04960
04902
04900
04961
04901
04963
04962
04970
04971
产品名:
MethoCult™ M3231
MethoCult™ GF M3434
MethoCult™ GF M3434
MegaCult™-C胶原和无细胞因子培养基
胶原蛋白溶液
MegaCult™-C无细胞因子培养基
MegaCult™-C胶原和含细胞因子培养基
MegaCult™-C含细胞因子培养基
双室载玻片套件
MegaCult™-C CFU-Mk染色试剂盒
MegaCult™-C无细胞因子全套试剂盒
MegaCult™-C含细胞因子全套试剂盒
Vodyanik MA et al. (SEP 2006)
Blood 108 6 2095--105
Leukosialin (CD43) defines hematopoietic progenitors in human embryonic stem cell differentiation cultures.
During hematopoietic differentiation of human embryonic stem cells (hESCs),early hematopoietic progenitors arise along with endothelial cells within the CD34(+) population. Although hESC-derived hematopoietic progenitors have been previously identified by functional assays,their phenotype has not been defined. Here,using hESC differentiation in coculture with OP9 stromal cells,we demonstrate that early progenitors committed to hematopoietic development could be identified by surface expression of leukosialin (CD43). CD43 was detected on all types of emerging clonogenic progenitors before expression of CD45,persisted on differentiating hematopoietic cells,and reliably separated the hematopoietic CD34(+) population from CD34(+)CD43(-)CD31(+)KDR(+) endothelial and CD34(+)CD43(-)CD31(-)KDR(-) mesenchymal cells. Furthermore,we demonstrated that the first-appearing CD34(+)CD43(+)CD235a(+)CD41a(+/-)CD45(-) cells represent precommitted erythro-megakaryocytic progenitors. Multipotent lymphohematopoietic progenitors were generated later as CD34(+)CD43(+)CD41a(-)CD235a(-)CD45(-) cells. These cells were negative for lineage-specific markers (Lin(-)),expressed KDR,VE-cadherin,and CD105 endothelial proteins,and expressed GATA-2,GATA-3,RUNX1,C-MYB transcription factors that typify initial stages of definitive hematopoiesis originating from endothelial-like precursors. Acquisition of CD45 expression by CD34(+)CD43(+)CD45(-)Lin(-) cells was associated with progressive myeloid commitment and a decrease of B-lymphoid potential. CD34(+)CD43(+)CD45(+)Lin(-) cells were largely devoid of VE-cadherin and KDR expression and had a distinct FLT3(high)GATA3(low)RUNX1(low)PU1(high)MPO(high)IL7RA(high) gene expression profile.
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产品类型:
产品号#:
04435
04445
04960
04902
04900
产品名:
MethoCult™ H4435 Enriched
MethoCult™ H4435 Enriched
MegaCult™-C胶原和无细胞因子培养基
胶原蛋白溶液
MegaCult™-C无细胞因子培养基
Fé et al. (MAR 2006)
The Journal of clinical investigation 116 3 715--23
Blocking the alpha 4 integrin-paxillin interaction selectively impairs mononuclear leukocyte recruitment to an inflammatory site.
Antagonists to alpha4 integrin show promise for several autoimmune and inflammatory diseases but may exhibit mechanism-based toxicities. We tested the capacity of blockade of alpha4 integrin signaling to perturb functions involved in inflammation,while limiting potential adverse effects. We generated and characterized mice bearing a Y991A mutation in alpha4 integrin [alpha4(Y991A) mice],which blocks paxillin binding and inhibits alpha4 integrin signals that support leukocyte migration. In contrast to the embryonic-lethal phenotype of alpha4 integrin-null mice,mice bearing the alpha4(Y991A) mutation were viable and fertile; however,they exhibited defective recruitment of mononuclear leukocytes into thioglycollate-induced peritonitis. Alpha4 integrins are essential for definitive hematopoiesis; however,the alpha4(Y991A) mice had intact lymphohematopoiesis and,with the exception of reduced Peyer's patches,normal architecture and cellularity of secondary lymphoid tissues. We conclude that interference with alpha4 integrin signaling can selectively impair mononuclear leukocyte recruitment to sites of inflammation while sparing vital functions of alpha4 integrins in development and hematopoiesis.
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