RESUMEN
Utilizing multiparameter flow cytometry, we have defined a subset of bone marrow cells containing lymphoid-restricted differentiation potential after i.v. transplantation. Bone marrow cells characterized by expression of the Sca-1 and c-kit Ags and lacking Ags of differentiating lineages were segregated into subsets based on allele-specific Thy-1.1 Ag expression. Although hematopoietic stem cells were recovered in the Thy-1.1low subset as previously described, the Thy-1.1neg subset consisted of progenitor cells that preferentially reconstituted the B lymphocyte lineage after i.v. transplantation. Recipients of Thy-1.1neg cells did not survive beyond 30 days, presumably due to the failure of erythroid and platelet lineages to recover after transplants. Thy-1.1neg cells predominantly reconstituted the bone marrow and peripheral blood of lethally irradiated recipients with B lineage cells within 2 weeks, although a low frequency of myeloid lineage cells was also detected. In contrast, myeloid progenitors outnumbered lymphoid progenitors when the Thy-1.1neg population was assayed in culture. When Thy-1. 1low stem cells were rigorously excluded from the Thy-1.1neg subset, reconstitution of T lymphocytes was rarely observed in peripheral blood after i.v. transplantation. Competitive repopulation studies showed that the B lymphoid reconstitution derived from Thy-1.1neg cells was not sustained over a 20-wk period. Therefore, the Thy-1. 1neg population defined in these studies includes transplantable, non-self-renewing B lymphocyte progenitor cells.
Asunto(s)
Subgrupos de Linfocitos B/trasplante , Células de la Médula Ósea/inmunología , Trasplante de Médula Ósea/inmunología , Refuerzo Inmunológico de Injertos/métodos , Animales , Subgrupos de Linfocitos B/citología , Subgrupos de Linfocitos B/metabolismo , Células de la Médula Ósea/citología , Células de la Médula Ósea/metabolismo , Diferenciación Celular/inmunología , Linaje de la Célula/inmunología , Separación Celular , Ensayo de Unidades Formadoras de Colonias , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/inmunología , Células Madre Hematopoyéticas/metabolismo , Transfusión de Linfocitos , Ratones , Ratones Congénicos , Ratones Endogámicos C57BL , Proteínas Proto-Oncogénicas c-kit/biosíntesis , Quimera por Radiación/inmunología , Antígenos Thy-1/biosíntesisRESUMEN
The kinetics of blood and organ engraftment following transplants of defined populations of hematopoietic stem/progenitor cells were investigated utilizing cell populations defined by surface antigen and rhodamine-123 staining. While long-term repopulating stem cells, short-term multipotent progenitors and committed progenitors all reconstituted peripheral blood red cells and splenic cellularity, only the population of cells that includes highly enriched long-term repopulating stem cells (Thy-1.1lowLinnegSca-1+Rh123low) reconstituted marrow cellularity. In addition, peripheral blood platelet and nucleated cell count increased only after transplant of the long-term repopulating population. These results argue that the major cell population that functions to reconstitute hematopoiesis after bone marrow transplantation is a primitive, marrow-homing stem cell. Transplantation of highly enriched multipotent progenitors that lack long-term reconstituting potential had no impact on hematopoietic recovery, apart from a transient increase in circulating erythrocytes. These results suggest that the primary cell population that functions to reconstitute hematopoiesis in a transplant setting is the long-term repopulating stem cell. This observation is discussed in the context of the normal hematopoietic process.