Maturation sequence hierarchy of murine macrophage progenitor cells

The heterogeneity of murine macrophage progenitors was analyzed with special interest in their maturation sequence. The gross appearance of macrophage colonies formed by C57BL/6 marrow cells was classified into three types: compact, intermediate, and dispersed. Progenitors of each type could be segregated by sedimentation velocity. Findings of cell-cycle studies showed that different types of colonies were not derived from a single progenitor cell at different times in the cell cycle. Therefore, it is considered that the difference in colony types can be attributed to the heterogeneity of progenitors. Suspension cultures of fractionated marrow cells rich in compact, intermediate, and dispersed colonies yielded mainly intermediate colonies, dispersed colonies, and clusters, respectively. As suspension cultures containing colony stimulating factor were considered to induce cell division as well as maturation, it is supposed that progenitors of compact, intermediate, and dispersed colonies constitute a maturation sequence hierarchy in this order.