AJP - Lung Cellular and Molecular Physiology, Vol 267, Issue 6 775-L785, Copyright © 1994 by American Physiological Society

ARTICLES

A discrete subpopulation of human monocytes expresses a neutrophil-like proinflammatory (P) phenotype

C. A. Owen, M. A. Campbell, S. S. Boukedes, R. A. Stockley and E. J. Campbell
Department of Medicine, University of Utah Health Sciences Center, Salt Lake City 84132.

We have demonstrated that a discrete and naturally occurring subpopulation 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 matrix through high-level cell-surface expression of alpha 5-, beta 1-, and beta 2-integrins; 2) high capacity to produce reactive oxygen species; 3) high content of serine proteinases and alpha 1-proteinase inhibitor; and 4) proteolytic activity against a soluble peptide human leukocyte elastase substrate, [3H]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 potential but contain the population of monocytes with high-level expression of HLA-DR antigen. P monocytes can readily be separated from the remainder of monocytes on the basis of 1) their capacity to adhere to fibronectin; and 2) their absent expression of HLA-DR antigen when flow cytometry or immunomagnetic beads are used. Our data indicate that, when recruited to sites of inflammation, P monocytes can either promote resolution of inflammation or contribute to tissue injury.

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