Predominance of macrophage-colony formation in human cord blood.

To clarify understanding of the characteristics of granulopoiesis during early infancy, we investigated the colony-forming unit in culture (CFUC), in cord blood (CB), in peripheral blood (PB), and in bone marrow (BM) of infants. The macrophage-colonies (M-colonies) were always predominant in the study of colony formation by CB and PB cells from infants, regardless of the source of the CSF used. This result contradicts previous reports which concluded that the colonies were mainly granulocytic type. In the colony formation by BM cells from one-month-old infants, the ratio of M-colonies was significantly higher than that of adult BM cells. The CSF produced by CB and PB mononuclear cells (MNC) from infants stimulated neutrophil-colony formation in the adult BM cells.