ISOLATION AND CHARACTERIZATION OF 4 CSF-1-DEPENDENT PLACENTAL MACROPHAGE CELL-LINES

By selection and cloning in the presence of colony-stimulating factor 1 (CSF-1), we have obtained from separate explants of individual 12- or 13-day mouse placentas four clonal cell lines dependent on CSF-1 for survival and growth in culture. All four cell lines show characteristics consistent with their derivation from placental macrophages. We describe the effects of CSF-1 on growth, morphology, and CSF-1 receptor phosphorylation. One cell line, JPL2A, which shows relatively complete growth arrest in the absence of CSF-1, was characterized in detail with respect to the effects of CSF-1 on DNA synthesis and protein turnover and its response to the duration of CSF-1 stimulation. In contrast to previous studies, our results suggest that extended stimulation leads to continuous recruitment of cells competent to reenter the cell cycle. These findings are discussed in terms of growth factor effects on the cell cycle and the usefulness of these cell lines for further study of growth factor signal transduction in macrophages.