Heterogeneity of Procoagulant Activity and Cytokine Release in Subpopulations of Alveolar Macrophages and Monocytes

We have studied the expression of tissue factor (TF) and fibrinopeptide A (FPA) generation as well as the release capacity of TNF-, IL-1, and IL-6 in density-defined subpopulations of alveolar macrophages (AM) and monocytes (Mo). TF was equally expressed on all AM subpopulations and Mo, while the FPA-forming capacity was at the same level in low density AM as in Mo and was significantly (P < 0.05) higher in low density AM than in high density AM. The lipopolysaccharide (LPS)-induced release of TNF- was higher (P < 0.05) in high density AM than in low density AM and in Mo. IL-1 release was undetectable in unstimulated AM and in LPS-stimulated low density AM, while the LPS-induced IL-1 release in high density AM was low compared to the levels demonstrated in Mo. LPS-stimulated IL-6 release was not distinctively different in the AM subpopulations and Mo. The presented study showed that FPA generation and LPS-stimulated TNF- release were dependent on the density (i.e., maturity) of AM. This implies that a skewed distribution of AM subpopulations induced by disease processes may profoundly influence the inflammatory reactions, including extravascular activation of coagulation.