Bipotential B-macrophage progenitors are present in adult bone marrow

According to the current model of adult hematopoiesis, differentiation of p luripotential hematopoietic stem cells into common myeloid- and lymphoid-co mmitted progenitors establishes an early separation between the myeloid and lymphoid lineages. This report describes a rare and previously unidentifie d CD45R-CD19(+) B cell progenitor population in postnatal bone marrow that can also generate macrophages. In addition to the definition of this B-line age intermediate, the data indicate that a developmental relationship betwe en the B and macrophage lineages is retained during postnatal hematopoiesis .