Isolation of a candidate human hematopoietic stem-cell population

In vivo models of human lymphopoiesis and autoimmunity in severe combined immune deficient mice

The discovery of the SCID mouse mutation has been an important advance for the study of human lymphopoiesis and autoimmunity. Further work in the SCID mouse models described in this review should yield important new information related to transplantation of human hematopoietic stem cells across HLA barriers, characterization of hematopoietic development in vivo, and identification of pathogenic human T cell clones in organ-specific autoimmune diseases. If pluripotent hematopoietic stem cells and pathogenic autoimmune T cells can be defined using SCID mouse recipients, this would pave the way for development of novel strategies for bone marrow transplantation and for interventional immunotherapy of autoimmune diseases targeted at the T cell receptor (99).

Characteristics of the hematopoietic stem cell compartment in adult mice

Mouse hematopoietic stem cells can be enriched from adult bone marrow by a number of methods. The resulting cell populations are heterogeneous in function, suggesting a complex organizational structure within the stem cell compartment. Several assays can be applied to the study of early stages of hematopoiesis; however clonal assays for long-term repopulation, the most critical operational definition of hematopoietic stem cells, are lacking. Further complicating the prospect of understanding early hematopoiesis is the finding that genetic variations among laboratory strains of mice lead to major differences in phenotypic and functional characteristics of hematopoietic stem cells. Application to the human situation of the methodology developed for stem cell isolation and characterization in the mouse will be hampered by the possibility of genetic variations among human subjects and the lack of a well-characterized assay system to detect and quantify cells capable of long-term repopulation of irradiated recipients.

Use of the Polymerase Chain Reaction for the Detection of Tumor Cell Involvement of Bone Marrow and Peripheral Blood: Implications for Purging

Bone marrow purging is being performed increasingly in an effort to deplete residual tumor cells from the graft prior to reinfusion. Several studies have suggested that the removal of tumor cells is an important clinical goal. In this review the utility of the polymerase chain reaction (PCR) for the detection of small numbers of tumor cells in bone marrow and peripheral blood is discussed. Using sensitive assays such as PCR, it is expected that the efficacy of bone marrow purging strategies will be improved and this will hopefully result in decreased relapse rates following autologous bone marrow transplantation.