Abstract: The invention relates to methods of obtaining compositions enriched in hematopoietic stem cells by separating out an enriched fraction of cells expressing the marker CDw109. Methods of obtaining compositions enriched in hematopoietic megakaryocyte progenitor cells are also provided. Compositions enriched for stem cells and populations of cells obtained therefrom are also provided by the invention. Methods of use of the cells are also included.

Abstract: Methods and DNA cloning vectors are provided for obtaining genes encoding secreted proteins and cell surface proteins.

Abstract: The invention provides methods for screening agents for potential anti-viral effects by assessing the ability of the agents to suppress viral replication and/or pathology in thymic cells grown in thymic organ culture in vitro. Also provided are methods to study viral pathology and infectivity.

Abstract: A method for initiating metastasis of human tumor cells under experimental conditions is provided. Immunocompromised non-human mammals having a viable, xenogeneic organ or tissue are used as a host for human tumor cells. The cells are introduced into the chimeric animal after the solid tissue is implanted and are then able to grow and metastasize as they would in situ. Therapeutic regimens may be evaluated in this system to determine efficacy against metastatic processes.

Abstract: Human hematopoietic stem cells are identified according to expression of specific cell surface markers. Substantially homogenous stem cell compositions are obtained by selective isolation of cells free of markers associated with differentiated cells, while displaying epitopic characteristics associated with the stem cells. The stem cells may then 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: Chimeric immunocompromised hosts are provided, comprising human bone marrow of at least 4 weeks from the time of implantation. The bone marrow is found to assume the normal population of bone marrow except for erythrocytes. The bone marrow may be used to study the effect of various agents on the proliferation and differentiation of hematopoietic cells.

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: A method is provided for screening compounds for the ability to supress thymocyte depletion in thymuses of HIV-infected individuals, particularly enhancing the CD4.sup.+ -expressing population as compared to an untreated individual. Particularly, drugs are provided which allow for this result, cyclosporine A being exemplary.

Abstract: The invention provides methods for screening agents for potential anti-viral effects by assessing the ability of the agents to suppress viral replication and/or pathology in thymic cells grown in thymic organ culture in vitro. Also provided are methods to study viral pathology and infectivity.

Abstract: Primordial tissue is introduced into immunodeficient hosts, where the primordial tissue develops and differentiates. The chimeric host allows for investigation of the processes and development of the xenogeneic tissue, testing for the effects of various agents on the growth and differentiation of the tissue, as well as identification of agents involved with the growth and differentiation.

Abstract: Immunocompromised hosts comprising xenogeneic fetal lymph node tissue implanted in the ear pinna are provided. The chimeric hosts are prepared by inserting the xenogeneic lymph node tissue into the ear pinna and closing the incision. The tissue is found to be rapidly vascularized and can be productively infected with HIV.

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: Hematopoietic cell populations are separated to provide cell sets and subsets as viable cells with high purity and high yields, based on the number of original cells present in the mixture. High-speed flow cytometry is employed using light characteristics of the cells to separate the cells, where high flow speeds are used to reduce the sorting time.

Abstract: Methods and chimeric immunocompromised hosts comprising functional xenogeneic organs are provided, particularly hematopoietic organs, where the xenogeneic organ is engrafted into a mammary fat pad. Exemplary is the engrafting of lymph node with mesenteric tissue comprising small portions of blood vessels transplanted into mammary fat pad of a scid/scid mouse. The engraftment in the mammary fat pad provides for efficiencies in transplantation, higher success rate of transplantation, and improved growth of the transplanted organ.

Abstract: Human lymphoid tissue is introduced into an immunocompromised host to provide opportunities to investigate the effect of stimuli on the human immune system and obtain information and products from the stimulus. Particularly, methodology is provided for the production of human monoclonal antibodies by introducing lymphoid tissue into an immunocompromised host, stimulating the B-lymphocytes with an appropriate immunogen, harvesting the tissue and immortalizing and/or cloning the B-lymphocytes under conditions to obtain a stable supply of monoclonal antibodies.

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 mammalian hematopoietic cells. Target cell populations include human stem cells.

Abstract: Methodology is provided for identifying the presence of human T-lymphocyte progenitor cells. Human thymus tissue is depleted of endogenous lymphold cells, repopulated with a human cellular composition which is HLA mismatched with the thymus tissue and implanted into a vascularizable site in an immunocompromised host. After at least about 2 weeks, the tissue may be assayed for the presence of the HLA mismatched T-lymphocytes as indicative of human T-lymphocyte progenitors in this cellular composition.

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.