Ca. Owen et al., A DISCRETE SUBPOPULATION OF HUMAN MONOCYTES EXPRESSES A NEUTROPHIL-LIKE PROINFLAMMATORY (P) PHENOTYPE, American journal of physiology. Lung cellular and molecular physiology, 11(6), 1994, pp. 120000775-120000785
We have demonstrated that a discrete and naturally occurring subpopula
tion of human monocytes expresses a neutrophil-like proinflammatory (P
) phenotype. P monocytes constitute 20-30% of the circulating monocyte
pool and are characterized by 1) avid adherence to extracellular matr
ix through high-level cell-surface expression of alpha(5-), beta(1-),
and beta(2)-integrins; 2) high capacity to produce reactive oxygen spe
cies; 3) high content of serine proteinases and alpha(1)-proteinase in
hibitor; and 4) proteolytic activity against a soluble peptide human l
eukocyte elastase substrate, [H-3]elastin, and solid-phase fibronectin
, even in the presence of proteinase inhibitors. However, P monocytes
express little or no cell-surface HLA-DR antigen, suggesting that they
are unable to participate in specific immune responses. In contrast,
the remainder of circulating monocytes have a low proinflammatory pote
ntial but contain the population of monocytes with high-level expressi
on of HLA-DR antigen. P monocytes can readily be separated from the re
mainder of monocytes on the basis of 1) their capacity to adhere to fi
bronectin; and 2) their absent expression of HLA-DR antigen when flow
cytometry or immunomagnetic beads are used. Our data indicate that, wh
en recruited to sites of inflammation, P monocytes can either promote
resolution of inflammation or contribute to tissue injury.