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.