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Query: UNIPROT:P10721 (c-kit)
 6,575 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

CD34, a stem cell marker, has been shown to be expressed on human CD3-CD4-CD8- (triple-negative; TN) thymocytes. Phenotypic and functional analyses suggest the following differentiation sequence: CD34+1-3-4-8(-)--> CD34+1+3-4 +/- 8(-)-->CD34-1+3-4+8(+/-)-->CD34-1++3-4+8+. In this report, we examined cytokine receptor gene expression on these subsets by reverse transcription-polymerase chain reaction analysis (RT-PCR). We were able to detect interleukin-7 receptor (IL-7R), c-kit and IL-2R gamma in all CD34+ thymocyte subsets, consistent with previous functional studies. We found IL-1R, granulocyte/macrophage colony-stimulating factor receptor-alpha and IL-4R transcripts in CD3- and CD34+ subsets. Secondly, we investigated T cell receptor (TCR)-delta and -beta gene rearrangement and transcription in CD34+ thymocytes. Our results show that a full-length TCR-delta transcript and the recombination activating genes RAG-1 and RAG-2 mRNA were already expressed in the CD34+1- subset. Mature V beta-containing TCR transcripts were also detected in the CD34+1+ subset, but not in the CD1- fraction. Furthermore, PCR analysis of D-J beta gene rearrangements showed that > or = 70% of CD34+1- cells are in a TCR beta germ-line configuration, although D-J beta recombination had already started in this population.
Eur J Immunol 1995 Sep
PMID:CD34-positive early human thymocytes: T cell receptor and cytokine receptor gene expression. 758 13

Natural killer (NK) cells are large granular lymphocytes thought to be important in the host's early immune response to viral infection and malignant transformation. NK cells proliferate and display enhanced cytotoxic activity in response to the T cell growth factor, interleukin 2 (IL-2). Stem cell factor or steel factor (SF) is the ligand for the c-kit receptor, and when combined with other hematopoietic growth factors, SF synergistically promotes the proliferation and differentiation of bone marrow stem cells. In the present study we show the c-kit receptor to be uniquely expressed on a subset of resting human NK cells (CD56bright) which constitutively expresses both the high affinity IL-2 receptor (IL-2R) and the intermediate affinity IL-2R. Other lymphocyte populations, including CD56dim NK cells, did not appear to express the c-kit receptor. Within the CD56bright NK cell subset, SF alone had no obvious effect on proliferation or cytotoxic activity. SF was shown to significantly augment the proliferative effect of IL-2, and caused a marked shift in the dose-response curve at IL-2 concentrations that selectively saturate the high affinity IL-2R. The potentiating effect of SF on NK cell proliferation was dependent on IL-2 binding to the high affinity IL-2R, and was blocked by a monoclonal antibody directed against the c-kit receptor. SF did not enhance proliferation at higher IL-2 concentrations that saturate the intermediate affinity IL-2R, nor did SF enhance IL-2-induced cytotoxic activity. Together, these data indicate that SF and IL-2 act synergistically to directly augment the proliferative capacity of a unique human NK cell subset constitutively expressing the high affinity IL-2R and the c-kit receptor. The implications of these findings on NK cell development and the host's early immune response to pathogen invasion are discussed.
J Exp Med 1993 Sep 01
PMID:Expression of a functional c-kit receptor on a subset of natural killer cells. 768 85

We previously described that cells with a CD34+CD71lo phenotype from adult human bone marrow are maintained at constant numbers in long-term suspension cultures supplemented with interleukin-6 (IL-6), IL-3, mast growth factor (MGF) (a c-kit ligand), and erythropoietin (Epo). In view of the large increase in cell numbers in such cultures (for example, > 10(6)-fold per cell), this was an unexpected finding. The following models for the observed maintenance of CD34+CD71lo cells in our cultures were considered: (1) survival of non-dividing cells; (2) self-renewal balanced by loss of cells; (3) asymmetrical divisions; and (4) combinations of the above. Two experimental strategies were explored to discriminate between these models. In the first, sorted CD34+CD45RAloCD71lo cells were labeled with the flourescent tracking dye PKH26, followed by analysis of PKH26 fluorescence of CD34+CD71lo and other cells present in the cultures at various times (up to 11 weeks). In the second approach, single CD34+CD45RAloCD71lo cells were directly sorted into individual wells, and growing cells were then analyzed by flow cytometry. Results from these experiments indicated a considerable variability in (1) the number of surviving input cells (ranging from 30 to 80%); (2) the proportion of cells that contributed significantly to the total cell production measured at day 20 (ranging from 1 to 5%); and (3) the number of CD34+ cells present in individual clones. Taken together, the observed maintenance of primitive CD34+ cells in our cultures apparently involves a combination of survival of CD34+CD71lo cells with a vary low turnover together with a very limited production of CD34+ cells. Clonal heterogeneity, differences in cell cycle kinetics between CD34+ and CD34- cells, and observations that the majority of bone marrow-derived CD34+CD45RAloCD71lo cells do not show a rapid proliferative response to a mixture of IL-6, IL-3, MGF, and Epo will have to be taken into account in the development of experimental strategies aimed at clinically useful expansion of primitive hematopoietic cells ex vivo.
Exp Hematol 1993 Sep
PMID:Maintenance of hematopoiesis in serum-free bone marrow cultures involves sequential recruitment of quiescent progenitors. 768 81

Modulation of expression of the c-kit proto-oncogene product, the receptor for the recently identified stem cell factor, was studied on 12-O-tetradecanoylphorbol-13-acetate (TPA)-stimulated cultures of CD34+ normal bone marrow progenitor cells, blast cells from patients with primary acute myelogenous leukemia, cells from the leukemia cell lines HEL and MO7E, as well as cultured HMC-1 mast cells. Expression of c-kit was assessed on both RNA and protein level employing standard Northern blotting, reverse transcription, and polymerase chain reaction-based Southern blotting, as well as cell surface labeling with anti-c-kit mAb YB5.B8. Treatment of virtually all cell types with nontoxic concentrations of TPA (10(-9) M) for at least 48 h was associated with down-regulation of synthesis of c-kit transcripts and stem cell factor-receptor surface expression. Studies on the mechanism of action of TPA utilizing the HEL erythroleukemia line showed that TPA was primarily acting by accelerating the turnover of c-kit RNA most likely through induction of a destabilizing protein. The effect of TPA on c-kit expression levels was independent of TPA-mediated induction of differentiation since other compounds including IFN-gamma, vitamin D3, retinoic acid, arabinofuranosylcytosine, butyric acid, and camptothecin, which also effectively induced differentiation of HEL cells, failed to alter levels of c-kit expression.
J Immunol 1993 Sep 01
PMID:Phorbol ester 12-O-tetradecanoylphorbol-13-acetate down-regulates expression of the c-kit proto-oncogene product. 768 5

The mRNAs encoding the c-kit protooncogene tyrosine kinase receptor and its ligand, hemopoietic stem cell factor, are coexpressed in the majority of small cell lung cancer cell lines, suggesting that an autocrine growth loop may exist. Functional c-kit protein levels correspond well with mRNA levels in these cells. We have observed that those cell lines which express the c-kit gene also express either the L- and N-myc genes; those cell lines which express the c-myc gene do not express the c-kit gene. We have determined, by analyzing several small lung cancer cell lines transfected with a c-myc expression vector, that heterologous expression of c-myc correlates with a marked down-regulation of c-kit expression. Regulation of c-kit expression by the myc gene family may be partly responsible for the differing biological properties of cell lines and tumors which express N- and L-myc versus those that express c-myc.
Cancer Res 1993 Sep 15
PMID:c-myc expression correlates with suppression of c-kit protooncogene expression in small cell lung cancer cell lines. 768 33

In this paper we attempt to improve upon the methods of hematopoietic stem cell expansion. We evaluate the effects of recombinant human stem cell factor (SCF or c-kit ligand) alone and also in combination with recombinant human granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin 3 (IL-3), on cell proliferation and differentiation in human long term bone marrow cultures (LTBMC). Weekly addition of 5 ng/ml of SCF with 25% serum containing media resulted in increased recovery of total nonadherent cells, granulocyte-macrophage colony forming units (CFU-GM), and burst-forming units erythroid (BFU-E) at week 1, but the number of bone marrow (BM) progenitor cells fell below the level of untreated control cultures at weeks 3 (BFU-E) and 4 (CFU-GM). At week 8, when the cultures were terminated, the CFU-GM recovery was markedly reduced in flasks supplemented with SCF compared with the controls (p < 0.002). Moreover, SCF treatment induced the early disappearance of BFU-E. When LTBMC were supplemented with the combination of SCF plus GM-CSF (100 U/ml) and IL-3 (5 ng/ml), synergistic activity of the CSFs was observed at week 1. The number of BM colony forming cells (CFC) rapidly declined below the level of growth factor-free controls, leading to the early exhaustion of the culture when SCF was combined with GM-CSF. By comparison, GM-CSF and IL-3 alone induced a statistically significant increase above the controls (no growth factor) in the number of nonadherent cell colonies of CFU-GM and BFU-E. Analysis of adherent layer cells from cultures supplemented with SCF showed increased cellularity, no adipogenesis, and early disappearance of myeloid progenitors while the percentage of CFU-GM in S phase, assessed by cytosine arabinoside (Ara-C) suicide assay, was 9.2 +/- 5% SD versus 27.7 +/- 10% SD in control (no growth factor) samples (p < 0.01). SCF increased the number of fibroblast colony forming units (CFU-F) and also showed a synergistic activity (9.6-fold increase) when combined with IL-3. These findings suggest that SCF, GM-CSF and IL-3 exert their activity on different cell populations within the hematopoietic system. Further investigations are needed to optimize the use of SCF in supporting hematopoiesis.
Stem Cells 1993 Sep
PMID:Effect of stem cell factor (c-kit ligand), granulocyte-macrophage colony stimulating factor and interleukin 3 on hematopoietic progenitors in human long-term bone marrow cultures. 769 21

The view that the two isoforms of prostaglandin-endoperoxide synthase (cyclooxygenase), PGHS-1 and PGHS-2, mediate physiologic and inflammatory processes, respectively, implies separate pathways of arachidonic acid metabolism with different benefits to the host. Functional segregation of these steps in endogenous arachidonic acid metabolism in a single cell in response to different stimuli is now demonstrated. When mouse bone marrow-derived mast cells developed in interleukin-3 (IL-3)-containing medium were cultured with c-kit ligand in combination with IL-10 and IL-1 beta, transient expression of PGHS-2 mRNA and protein occurred in a dose- and time-dependent fashion, accompanied by substantial release of prostaglandin D2 (PGD2) into the culture medium from 2 to 10 h. In contrast, induction of PGHS-2 did not mediate an increase in PGD2 generation in response to stimulation with IgE and antigen. After a longer period of culture, from 24 to 48 h, the expression of PGHS-1 increased, as did the increase in IgE/antigen-dependent generation of PGD2. Dexamethasone, which inhibited the induction of PGHS-2 but not PGHS-1, and a PGHS-2-selective inhibitor suppressed cytokine-induced PGD2 generation but not IgE-dependent PGD2 generation. Thus, at a time when both PGHS-1 and PGHS-2 are present in bone marrow-derived mast cells, they function independently by coupling to different stimulus-initiated pathways to PGD2 generation from endogenously derived arachidonic acid.
J Biol Chem 1994 Sep 02
PMID:Prostaglandin endoperoxide synthase-1 and -2 couple to different transmembrane stimuli to generate prostaglandin D2 in mouse bone marrow-derived mast cells. 807 53

Mast cells and basophils are offspring of the multipotential hematopoietic stem cell. Although mast cells sometimes are misunderstood as basophils that have invaded connective or mucosal tissue, these two kinds of basophilic cells are distinguishable by morphology and surface antigenicity. Developmental processes of mast cells and basophils are different. Basophils complete their differentiation within the bone marrow, but precursors of mast cells leave the bone marrow, invade connective or mucosal tissue, proliferate, and differentiate into mast cells. The mechanisms regulating development are different between mast cells and basophils. Both T cell-dependent and fibroblast-dependent mechanisms are involved in the development of rodent mast cells, but only the fibroblast-dependent mechanism is known for development of human mast cells and only the T cell-dependent mechanism for the development of basophils of both rodents and humans. The most important cytokine for the T cell-dependent mechanism appears to be interleukin-3, whereas for the fibroblast-dependent mechanism it appears to be the ligand for the c-kit receptor (ie, stem cell factor).
Am J Med Sci 1993 Sep
PMID:Development of mast cells and basophils: processes and regulation mechanisms. 812 82

In the accompanying paper we showed that six distinct subsets of bone marrow (BM) cells can be identified using the mAb ER-MP12 and ER-MP20 in two-colour immunofluorescence analysis. Upon intrathymic transfer into sublethally irradiated mice thymus-repopulating ability was restricted to ER-MP20- BM cells expressing either high or intermediate levels of the ER-MP12 antigen (1-2% and approximately 30% of BM nucleated cells respectively). The highest frequency of thymus-repopulating cells was found in the minor subset of ER-MP12(+)+20- BM cells. In the present study we demonstrate that upon intravenous transfer, thymus-homing and -repopulating BM cells are exclusively confined to the ER-MP12(+)+20- and ER-MP12+20- subpopulations, the highest frequency being detected among ER-MP12(+)+20- BM cells. Analysis of the peripheral blood leucocytes of reconstituted mice showed that not only prothymocytes but also progenitor cells of the B cell lineage as well as the myeloid lineage were present within both subsets. Three-colour flow cytometric analysis revealed that ER-MP12(+)+20- BM cells in particular were phenotypically heterogeneous with respect to the expression of the cell surface markers Thy-1, Sca-1, CD44, B220 and c-kit. Taken together our data demonstrate that ER-MP12 positively identifies BM cells with the ability to home to and repopulate the thymus. The phenotypic heterogeneity displayed by the ER-MP12(+)+20- BM subset, containing the highest frequency of thymus-homing and -repopulating cells, provides a basis for further separation of prothymocyte activity from other haematopoietic activities in the BM of the mouse.
Int Immunol 1993 Sep
PMID:ER-MP12 antigen, a new cell surface marker on mouse bone marrow cells with thymus-repopulating ability: II. Thymus-homing ability and phenotypic characterization of ER-MP12-positive bone marrow cells. 824 Oct 54

Analysis of the cellular/molecular basis of the early steps of hematopoietic proliferation and differentiation is hindered by the rarity of hematopoietic progenitors and stem cells (HP/HSC). The intensive efforts devoted to the development of purification methods for early HP and HSC, although initially largely unsuccessful, have recently provided a high level of HP/HSC yield and/or recovery. The methodology developed by our group, recently improved, provides not only virtually complete purification, but also abundant recovery of early HP/HSC such as colony forming units granulocyte/erythroid/macrophage/megakaryocyte (CFU-GEMM), burst forming units erythroid (BFU-E), CFU granulocyte/macrophage (CFU-GM)/CFU blast cells (CFU-B), and long-term culture initiating cells (LTC-IC) from adult peripheral and cord blood (CB). We have also developed a serum-free liquid suspension culture for unilineage erythroid (E), granulocytic (G) or monocytic (M) differentiation of stringently purified HP/HSC. These culture systems allow sequential collection and cellular/molecular analysis of discrete populations of hematopoietic cells at a homogenous stage of differentiation specifically along a unilineage pathway. These experimental tools have been utilized to investigate cellular/molecular mechanisms underlying early hematopoiesis. The transcription factor (TF) GATA-1 is considered to be the "master" gene of erythropoiesis. In highly purified HP/HSC undergoing E or GM differentiation, GATA-1 expression is characterized initially by proliferation-dependent activation and at later stages by sustained expression in the E pathway and suppression in the GM pathway. Hypothetically, similar on/off switches of lineage-restricted TF may underlie the binary fate decisions of early HP differentiation. The expression and modulation of hematopoietic growth factor receptors (HGFR) in early hematopoiesis have been extensively analyzed. The results suggest a model of transactivation cascade for HGFR such as interleukin 6 receptor (IL-6R), IL-3R, GM colony stimulating factor receptor (GM-CSFR), and erythropoietin receptor (EpR), whereby each HGF upmodulates the R(s) for distal-acting HGF(s). Finally, we have investigated the effect of HGF on reactivation of hemoglobin F (HbF) in clonogenic or liquid suspension serum-free culture of purified adult HP. The results suggest that c-kit ligand (KL) plays a key role in the reactivation of HbF synthesis in adult life, and IL-3/GM-CSF potentiate this effect at low KL level. The KL-induced HbF reactivation is seemingly related to an enhanced proliferation of early E progenitors in their differentiation pathway.
Stem Cells 1993 Sep
PMID:Stringently purified human hematopoietic progenitors/stem cells: analysis of cellular/molecular mechanisms underlying early hematopoiesis. 824 48


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