Differential Prostaglandin Production by Unfractionated and Density-Fractionated Human Monocytes and Alveolar Macrophages

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Abstract
Mononuclear phagocyte elaboration of E series prostaglandins (PGE) may be important in the regulation of inflammatory and fibrotic reactions. Mononuclear phagocytes are morphologically and functionally heterogeneous cells. To further understand the processes controlling inflammation and fibrosis, in particular that in the human lung, we characterized the ability of unfractionated and density-fractionated human alveolar macrophages and blood monocytes to elaborate PGE. Alveolar macrophages and blood monocytes constitutively elaborated small amounts of PGE, and their elaboration of PGE was increased with lipopolysaccharide (LPS) stimulation. Monocytes elaborated more PGE than autologous alveolar macrophages. In addition, denser monocytes (specific gravity > 1.055) and denser alveolar macrophages (specific gravity > 1.044) elaborated more PGE than less dense monocytes and alveolar macrophages, respectively. When monocytes were incubated in vitro, their constitutive PGE elaboration decreased with time. However, in vitro incubation did not cause monocytes to lose their capacity to elaborate PGE in response to LPS. Thus, mononuclear phagocyte populations differ in their ability to elaborate PGE. These differences can be only partially attributed to differences in cell maturation.