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