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Expression and modulation of a mononuclear phagocyte differentiation antigen (PAM-1) during in vitro maturation of
Abstract:
Human macrophages obtained by in vitro maturation of peripheral blood monocytes express a surface antigen, PAM-1, recognized by a monoclonal antibody and typical of pulmonary alveolar and tissue macrophages. PAM-1, undetectable in freshly isolated peripheral blood monocytes, was expressed in monocyte-derived macrophages after 3 days of in vitro adherent culture and was maximal after 14-15 days (50%-60% of positive cells). Similar levels of PAM-1 positivity were observed in non-adherent monocyte-derived macrophages suggesting that cell adhesion was not a critical requisite for the expression of this antigen. Bacterial lipopolysaccharide and a monocyte chemotactic protein preparation respectively suppressed and upregulated PAM-1 expression in monocyte-derived macrophages. In contrast, interferon-gamma, although enhancing the levels of class II HLA-DR antigen in monocyte-derived macrophages, did not influence the kinetics of appearance and the levels of PAM-1 in these cells. Thus, expression of PAM-1, which is restricted to certain stages of the monocyte-macrophage differentiation pathway, is also differentially modulated by activation signals, which can be present in the micro-environment of inflammed tissues.
Insights
Human macrophages develop a surface antigen, PAM-1, during in vitro maturation. This antigen
Area of Science:
- Immunology
- Cell Biology
Background:
- Human macrophages play crucial roles in immune responses.
- Monocyte differentiation into macrophages involves significant cellular changes.
- Specific surface antigens can serve as markers for macrophage differentiation stages.
Purpose of the Study:
- To characterize the expression of a novel surface antigen, PAM-1, during human monocyte differentiation into macrophages.
- To investigate the modulation of PAM-1 expression by various stimuli relevant to inflammatory microenvironments.
Main Methods:
- In vitro culture of human peripheral blood monocytes to induce macrophage differentiation.
- Flow cytometry analysis using a monoclonal antibody against PAM-1.
- Treatment of differentiating macrophages with bacterial lipopolysaccharide, monocyte chemotactic protein, and interferon-gamma.
Main Results:
- PAM-1 antigen expression was absent in freshly isolated monocytes but emerged during in vitro macrophage differentiation, peaking after 14-15 days.
- Cell adhesion was not essential for PAM-1 expression.
- Bacterial lipopolysaccharide suppressed PAM-1 expression, while monocyte chemotactic protein upregulated it.
- Interferon-gamma did not affect PAM-1 expression kinetics or levels, despite increasing HLA-DR antigen.
Conclusions:
- PAM-1 expression is a specific marker for a particular stage in the monocyte-macrophage differentiation pathway.
- The expression of PAM-1 is differentially regulated by inflammatory activation signals.
- PAM-1 modulation may provide insights into macrophage behavior within inflamed tissue microenvironments.