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Updated: Aug 30, 2026
Assessing Anti-fungal Activity of Isolated Alveolar Macrophages by Confocal Microscopy
Published on: July 9, 2014
Human alveolar macrophages are markedly deficient in REF-1 and AP-1 DNA binding activity
M M Monick1, A B Carter, G W Hunninghake
1Department of Medicine, University of Iowa College of Medicine and Veterans Affairs Medical Center, Iowa City, Iowa 52242, USA.
Abstract:
Although many functions of human alveolar macrophages are altered compared with their precursor cell, the blood monocyte (monocyte), the reason(s) for these functional changes have not been determined. We recently reported that human alveolar macrophages do not express AP-1 DNA binding activity (Monick, M. M., Carter, A. B., Gudmundsson, G., Geist, L. J., and Hunninghake, G. W. (1998) Am. J. Physiol. 275, L389-L397). To determine why alveolar macrophages do not express AP-1 DNA binding activity, we first showed that there was not a decrease in expression of the FOS and JUN proteins that make up the AP-1 complex. There was, however, a significant difference in the amounts of the nuclear protein, REF-1 (which regulates AP-1 DNA binding by altering the redox status of FOS and JUN proteins), in alveolar macrophages compared with monocytes. In addition, in vitro differentiation of monocytes to a macrophage-like cell resulted in decreased amounts of REF-1. Finally, addition of REF-1 from activated monocytes to alveolar macrophage nuclear proteins resulted in a marked increase in AP-1 DNA binding. These studies strongly suggest that the process of differentiation of monocytes into alveolar macrophages is associated with a loss of REF-1 and AP-1 activity. This observation may explain, in part, some of the functional differences observed for alveolar macrophages compared with monocytes.
Insights
Human alveolar macrophages lose AP-1 DNA binding activity due to decreased REF-1 protein during differentiation from monocytes. This REF-1 loss explains some functional differences between these immune cells.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Human alveolar macrophages exhibit altered functions compared to blood monocytes.
- Previous work showed alveolar macrophages lack AP-1 DNA binding activity.
Purpose of the Study:
- To investigate the reasons behind the lack of AP-1 DNA binding activity in alveolar macrophages.
- To determine the role of differentiation from monocytes in this functional change.
Main Methods:
- Compared FOS and JUN protein expression in alveolar macrophages and monocytes.
- Quantified nuclear REF-1 protein levels in both cell types.
- Assessed AP-1 DNA binding activity after adding REF-1 to alveolar macrophage nuclear proteins.
- Induced in vitro differentiation of monocytes and measured REF-1 levels.
Main Results:
- FOS and JUN protein expression was similar in alveolar macrophages and monocytes.
- Alveolar macrophages had significantly lower amounts of the nuclear protein REF-1 compared to monocytes.
- In vitro differentiation of monocytes into macrophage-like cells decreased REF-1 amounts.
- Adding REF-1 to alveolar macrophage nuclear proteins increased AP-1 DNA binding.
Conclusions:
- Differentiation of monocytes into alveolar macrophages is associated with a loss of REF-1.
- This loss of REF-1 leads to decreased AP-1 DNA binding activity.
- Reduced REF-1 and AP-1 activity may explain some functional differences in alveolar macrophages.
