DELINEATION OF THE HUMAN HEMATOLYMPHOID SYSTEM - POTENTIAL APPLICATIONS OF DEFINED CELL-POPULATIONS IN CELLULAR THERAPY

Hematopoietic stem cells (HSC) have the capacity to reconstitute all t he blood cells in the body. HSC are rare, representing on average 0.05 % of the mononuclear cells present in healthy human bone marrow. Due t o their capacity for self-renewal and their pluripotent, long-term rec onstituting potential, HSC are considered ideal for transplantation to reconstitute the hematopoietic system after treatment for various hem atologic disorders or as a target for the delivery of therapeutic gene s. Human HSC also have potential applications in restoring the immune system in autoimmune diseases and in the induction of tolerance for al logeneic solid organ transplantation. With the increased interest in h uman HSC for clinical applications, technology for the isolation of ca ndidate HSC and knowledge of human hematopoiesis have been growing rap idly. In this article, we discuss the functional characterization of a human CD34(+)Thy-1(+) HSC population which is essentially free of res idual disease, our efforts to generate alternate monoclonal antibodies for the isolation of clinically useful stem or progenitor cell popula tions, and the identification of a never lymphoid progenitor as part o f an exploration towards defining progenitors with potential applicati on as adjuncts to HSC-based cellular therapy.