Abstract: Myeloproliferative leukemia receptor (mpl) ligands, such as thrombopoietin, act on a primitive subpopulation of human stem cells having the characteristics of self-renewal and ability to give rise to all hematopoietic cell lineages. Thrombopoietin supports both megakaryocytic differentiation and primitive progenitor cell expansion of CD34+ and CD34+ sub-populations (CD34+Lin−, CD34+Thy-1+Lin−, and CD34+Lin− Rh123lo). Thrombopoietin also stimulated quiescent human stem cells to begin cycling. Thus, mpl ligands are useful for expanding primitive stem cells for restoration of hematopoietic capabilities and for providing modified human stem cells for gene therapy applications.

Abstract: A purified soluble form of Flk-2 is provided, as the DNA sequence and as the protein. In addition, a partial DNA sequence of the human Flk-2 is also provided. The proteins find use in modulating hematopoiesis in culture and in vivo, as well as for the production of antibodies for assays of the proteins.

Abstract: A human hematopoietic system is provided in an immunocompromised mammalian host, where the hematopoietic system is functional for extended periods of time. Particularly, human fetal liver tissue and human fetal thymus is introduced into an appropriate site of a young immunocompromised mouse at a site supplied with a vascular system, whereby the fetal tissue results in novel formation of functional human bone marrow tissue.

Abstract: Myeloproliferative leukemia receptor (mpl) ligands, such as thrombopoietin, act on a primitive subpopulation of human stem cells having the characteristics of self-renewal and ability to give rise to all hematopoietic cell lineages. Thrombopoietin supports both megakaryocytic differentiation and primitive progenitor cell expansion of CD34.sup.+ and CD34.sup.+ sub-populations (CD34.sup.+ Lin.sup.-, CD34.sup.+ Thy-1.sup.+ Lin.sup.-, and CD34.sup.+ Lin.sup.- Rh123.sup.lo). Thrombopoietin also stimulated quiescent human stem cells to begin cycling. Thus, mpl ligands are useful for expanding primitive stem cells for restoration of hematopoietic capabilities and for providing modified human stem cells for gene therapy applications.

Abstract: This invention provides a method for obtaining a recombinant retroviral packaging cell capable of producing retroviral vectors as well as the recombinant packaging cell obtained by the method. Also provided is a method of producing recombinant retroviral particles obtained by introducing into the packaging cells obtained according to the methods disclosed herein, a recombinant retroviral vector and propagating the resulting producer cells under conditions favorable for the production and secretion of retroviral vector supernatant. The retroviral supernatant produced by these methods also is claimed herein. This invention further provides a method for screening retroviral vector supernatant for high transduction efficiency and methods for producing retroviral vector supernatant for transducing cells with high efficiency in gene therapy applications.

Abstract: The invention relates to methods of enriching for hematopoietic cell populations enriched in myeloid and/or lymphoid progenitor cells based on cell specific markers. The methods also provide an enriched population of prethymic lymphoid-committed progenitor population lacking long-term hematopoietic reconstitution potential. Compositions enriched for the cells and populations of cells obtained therefrom are also provided by the invention. Methods of use of the cells are also included. Methods of genetically modifying the cells are provided as are cells obtained thereby.

Abstract: The invention relates to methods of enriching for hematopoietic cell populations enriched in myeloid and/or lymphoid progenitor cells based on cell specific markers. The methods also provide an enriched population of prethymic lymphoid-committed progenitor population lacking long-term hematopoietic reconstitution potential. Compositions enriched for the cells and populations of cells obtained therefrom are also provided by the invention. Methods of use of the cells are also included. Methods of genetically modifying the cells are provided as are cells obtained thereby.

Abstract: The invention relates to methods of enriching for hematopoietic cell populations enriched in myeloid and/or lymphoid progenitor cells based on cell specific markers. The methods also provide an enriched population of prethymic lymphoid-committed progenitor population lacking long-term hematopoietic reconstitution potential. Compositions enriched for the cells and populations of cells obtained therefrom are also provided by the invention. Methods of use of the cells are also included. Methods of genetically modifying the cells are provided as are cells obtained thereby.

Abstract: The present invention provides a method for optimizing gene transfer into hematopoietic stem cells (HSCs) by contacting the cells with hydroxyurea prior to gene transfer to induce HSCs in G0 into active cell cycle. This method is useful for treating patients suffering from a disease that is suitably treated by gene therapy or involves hematopoietic cells. A method is also provided for enhancing the efficacy of bone marrow transplantation by administering hydroxyurea to increase HSC yields.

Abstract: Human hematopoietic stem cells are provided by separation of the stem cells from dedicated cells. The stem cells may than be maintained by regeneration in an appropriate growth medium. Means are provided for assaying for the stem cells as to their capability for producing members of each of the hematopoietic lineages. A method for treating a human by implanting a cellular composition comprising greater than 90% human hematopoietic stem cells is also disclosed.

Abstract: This invention provides a method for obtaining a recombinant retroviral packaging cell capable of producing retroviral vectors and the recombinant packaging cell obtained by the method. Also provided is a method of producing recombinant retroviral particles obtained by introducing into the packaging cells obtained according to the methods disclosed herein, a recombinant retroviral vector and propagating the resulting producer cells under conditions favorable for the production and secretion of retroviral vector supernatant. The retroviral supernatants produced by these methods also is claimed herein. This invention further provides a method for screening retroviral vector supernatant for high transduction efficiency and methods for producing retroviral vector supernatant for transducing cells with high efficiency in gene therapy applications.

Abstract: This invention provides novel human growth factor polypeptides, nucleotides encoding the growth factor polypeptides, and uses for the growth factor polypeptides and polynucleotides.

Abstract: This invention provides a novel antibody, designated .alpha.EM10, and a hybridoma cell line that produces the .alpha.EM10 antibody. Also provided are methods to obtain compositions enriched for hematopoietic stem cells. The methods employ a separation technique utilizing antibodies (.alpha.EM10) specific for a unique cell marker (EM10) that is expressed on stem and progenitor cells, while being less accessible or absent on more mature cells. Further provided are cell compositions enriched for EM10+ cells.

Abstract: Human hematopoietic stem cells are provided by separation of the stem cells from dedicated cells. The stem cells may than be maintained by regeneration in an appropriate growth medium. Means are provided for assaying for the stem cells as to their capability for producing members of each of the hematopoietic lineages.

Abstract: The invention provides a method for both the positive and negative selection of at least one mammalian cell population from a mixture of cell populations utilizing a magnetically stabilized fluidized bed. One desirable application of this method is the separation and purification of hematopoietic cells. Target cell populations include human stem cells.

Abstract: Human hematopoietic stem cells are provided by separation of the stem cells from dedicated cells. The stem cells may than be maintained by regeneration in an appropriate growth medium. Means are provided for assaying for the stem cells as to their capability for producing members of each of the hematopoietic lineages.

Abstract: The present invention provides methods and bioreactors for expanding stem cells in a population of cells substantially enriched in hematopoietic stem cells and substantially free of stromal cells. The method comprising the steps of inoculating the population of cells in an expansion container in a volume of suitable medium such that the cell density is at least about 5,000 cells/1 mL and at an initial oxygen concentration of less than 8%; adding an effective amount of at least one cytokine to cause stem cell expansion; culturing the cells under suitable conditions such that the cells condition the medium; increasing the oxygen concentration to about 20%; exchanging the medium at a rate which allows expansion of the stem cells; and culturing the cells under conditions such that the stem cells are expanded. The present invention also provides a bioreactor constructed to accomodate the operational requirements for stroma-free stem cell expansion.

Abstract: Human hematopoietic stem cells are provided by separation of the stem cells from dedicated cells. The stem cells may than be maintained by regeneration in an appropriate growth medium. Means are provided for assaying for the stem cells as to their capability for producing members of each of the hematopoietic lineages.

Abstract: The present invention provides a simple and reliable means for isolating populations of hematopoietic cells enriched for stem cell activity on the basis of possession of high CD34 cell surface antigen density ("CD34hi"). CD34.sup.hi cell preparations are useful, for example, for drug discovery efforts, for reconstituting hematopoiesis in an animal lacking a functioning hematopoietic system, and for gene therapies.

Abstract: A method for obtaining human hematopoietic stem cells is provided by enrichment for stem cells using a novel stem cell marker. Compositions enriched for stem cells are obtained using novel antibody HCC-1 which is specific for a CD59 epitope highly accessible on stem cells, and less accessible or absent on mature cells. The enriched population of cells derived from these methods are also provided.