Sex-linked thymic epithelial hypoplasia in two siblings. Attempt at treatment by transplantation with fetal thymus and adult bone marrow

The biological restoration of central nervous system architecture and function: part 1-foundations and historical landmarks in contemporary stem cell biology

Since their discovery, stem cells have fascinated scientists with their ultimate potential: the ability to cure disease, repair altered physiology, and reverse neurological deficit. Stem cell science unquestionably promises to eliminate many of the tragic limitations contemporary medicine must acknowledge, and cloning may provide young cells for an aging population. Although it is widely believed that stem cells will transform the way medicine is practiced, therapeutic interventions using stem cell technology are still in their infancy. The 3 most common stem cell sources studied today are umbilical cord blood, bone marrow, and human embryos. Although cord blood is currently used to treat dozens of disorders and bone marrow stem cells have been used clinically since the 1960s, human embryonic stem cells have yet to be successfully applied to any disease. Undeniably, stem cell therapy has the potential to be one of the most powerful therapeutic options available. In this introductory article of a 5-part series on stem cells, we narrate the evolution of modern stem cell science, delineating major landmarks that will prove responsible for taking stem cell technology from the laboratory into revolutionary clinical applications: from the first milestone of identifying the mouse hematopoietic stem cell to the latest feats of producing pluripotent stem cells without embryos at all. In Part 2, we present the evidence demonstrating the certainty of adult mammalian neurogenesis; in Parts 3 and 4, we describe neurosurgical applications of stem cell technology; and in Part 5, we discuss the philosophical and ethical issues surrounding stem cell therapy, as well as future areas of exploration.

Preclinical experiments

The clinical use of autologous stem cell transplants for the treatment of refractory severe autoimmune diseases was preceded by convincing proof of its underlying principle in animal models. The various categories of experimental autoimmune disease in laboratory rodents are briefly described here, and the rationale that was used in the selection of suitable experimental autoimmune diseases for translational research is explained. The two models that provided the bulk of the data needed for designing the initial clinical treatment protocols were adjuvant arthritis (AA) and experimental allergic encephalomyelitis (EAE), which were both induced in Buffalo rats. In this strain, AA is manifested as a chronic, progressive, systemic polyarthritis and EAE as a chronic, remitting/relapsing form of encephalomyelitis resembling multiple sclerosis. Both diseases can be cured with autologous stem cell transplantation provided that adequate conditioning is given and that the disease has not yet progressed to the stage of 'scarring'. It is basically the inflammatory stages that respond well to this therapy. The success of treatment depends on how completely the autoantigen-specific activated T-lymphocytes and memory cells are eradicated. Because of a lack of information on the nature of the autoantigens involved in human disease and on the size of those cell populations in the animal models as well as in humans, this aspect of translation is difficult. The experiments have, however, provided important guidelines. High-dose conditioning regimens yield better results than low-dose conditioning, certain conditioning agents perform better than others, and care should be taken not to reintroduce too many T-cells with the autologous graft. The clinical results obtained so far indicate a high predictive power of these two animal models, which are therefore recommended strongly for additional preclinical studies.

In utero acute graft-versus-host disease in a neonate with severe combined immunodeficiency

We describe a male neonate with severe combined immunodeficiency who at birth had acute graft-versus-host disease (GVHD) as a result of maternal-fetal transfusion during pregnancy. Several clinical signs helped establish this diagnosis. Findings of a skin biopsy specimen confirmed the diagnosis of acute GVHD. Immunologic evaluation disclosed an absence of T and B lymphocytes. Acute GVHD in severe combined immunodeficiency most often occurs during the first weeks of life; intrauterine occurrence is unusual.

Graft-versus-host reaction following blood product transfusion

The observation of graft-versus-host (GVH) reaction after platelet transfusion in a patient with Hodgkin's disease led us to analyze 38 reported cases in the literature, to outline prognostic factors and to characterize patients at risk. Overall mortality was 68 percent. It was higher among children (76 percent) than among adults (62 percent), and among patients with Hodgkin's disease and immune deficiency syndromes (88 percent) than among those with leukemias (23 percent, p less than 0.005). Following blood transfusions from normal donors, mortality was higher (88 percent) than after transfusions from donors with chronic myelocytic leukemia (25 percent, p less than 0.05). Minimal lymphocyte doses necessary to cause GVH reaction are in excess of 10(7)/kg. Adults seem more resistant to homografts than do children, and the host's cellular immune status is of major prognostic importance. Lymphocytes from donors with chronic myelocytic leukemia may be deficient, and after a threshold dose, the number of lymphocytes transfused does not correlate with clinical outcome. Effective prophylactic measures do exist for this complication but satisfactory therapy does not.