Macrophage phenotype regulation by colony-stimulating factors at bone marrow level.

Macrophages (m phi s) can be divided into several subpopulations, which differ in phenotype, function, and localization patterns. However, little is known about the mechanisms that regulate this heterogeneity. We investigated whether m phi heterogeneity is regulated by colony-stimulating factors (CSFs) at the bone marrow level. By clonal expansion of bone marrow-derived precursor cells in the presence of CSF-1, granulocyte-macrophage CSF or multi-CSF (interleukin-3), phenotypic heterogeneity was observed between m phi colonies. Heterogeneity was found especially when different CSF culture conditions were used but also between m phi colonies derived under the same CSF culture condition. Our results illustrate that CSFs from the bone marrow hemopoietic microenvironment are important for the induction of phenotypic heterogeneity within the progeny of cloned m phi precursor cells during maturation and differentiation in vitro.