Regulation of macrophage and granulocyte proliferation. Specificities of prostaglandin E and lactoferrin

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Abstract
Hemopoietic colony-forming cells committed macrophage differentiation (M-CFC) were selectively and differentially inhibited by prostaglandin (PG)E. A hierarchy of sensitivity was observed among murine CFC stimulated by colony-stimulating factors (CSF) which differ in their ability to initiate proliferation of morphologically distinct colony types, or stimulation by CSF provided by macrophage feeder layers. Inhibition of macrophage colony formation to 50% levels occurred with PGE concentrations between 10-8-10-9 M, and was still evident at 10-10-10-11 M PGE concentrations. In mixed colonies containing macrophages and neutrophils, growth was less sensitive to the inhibitory effects of PGE. However, the monocytoid component of these colonies was reduced in the presence of PGE. Neutrophil progenitor cell proliferation was not influenced by PGE concentrations below 10-6 M, regardless of time of addition of PGE, whereas clonal macrophage expansion, and clone size, was sensitive to inhibition by PGE when added as late as 3 days after culture initiation. PGF2.alpha. was not inhibitory to colony formation. Experimental evidence for a selective role of macrophage PGE in the regulation of macrophage colony formation was directly provided by utilizing resident peritoneal macrophages as a source of CSF for bone marrow target cell overlays. Simultaneous morphological analysis of colonies proliferating in bilayer culture in response to increasing concentrations of macrophages and direct measurements of PGE synthesized by an identical number of macrophages maintained in liquid culture, demonstrate that a specific decline in macrophage colony formation occurs coincident with a linear increase in macrophage PGE synthesis. Inhibition of macrophage PGE synthesis by indomethacin resulted in the specific enhancement of macrophage colony formation. Macrophage PGE synthesis was induced by CSF preparations with the selective capacity to differentially stimulate macrophage proliferation, but not by those which preferentially stimulate granulocyte colony formation. In comparison to the effects of PGE on M-CFC polymorphonuclear granulocyte-derived lactoferrin (LF) reduced macrophage production of colony-stimulating activities for macrophage, mixed macrophage-neutrophil and neutrophil colony formation. The ability of LF to reduce macrophage PGE synthesis, presumably by decreasing CSF production, suggested that LF and PGE can interact in the control of macrophage and granulocyte proliferation.