Purification and expansion of human hematopoietic stem/progenitor cells

CD34 monoclonal antibodies bind selectively to the most immature 1.5% of low-density human bone marrow mononuclear cells, including terminal deoxynucleotidyl transferase-positive lymphoid precursor cells, all types of in vitro assayed hematopoietic progenitor cells, and lymphohematopoietic stem cells capable of reconstituting myeloablated humans in clinical transplantation. Positive selection of highly enriched CD34+ stem and progenitor cells is widely used in research and is now being investigated in many applications of autologous and allogeneic clinical transplantation. More highly purified stem cells are also desired in research and may have clinical use. Immunoaffinity isolation of CD34+ cell subsets using antibodies against CD38 permits 10-100-fold further purification of stem cells. It will be valuable to be able to expand stem and progenitor cells from small marrow and blood samples. We are now identifying the genes expressed in stem and progenitor cells to eventually allow the control of stem and progenitor cell survival, proliferation, and differentiation.