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Morphologic and molecular changes in target cells during in vitro interaction with macrophages
Abstract:
Recent work has indicated that macrophages can affect eukaryote cells in a variety of ways. The inhibitory or enhancing effects on target cell proliferation are mediated by soluble factors released from macrophages and appear to affect every replicating cells. Macrophages have also been shown to affect target cell viability and this destructive potential was initially considered to be tumor-specific. The present work further assesses these macrophage effects on targets by morphologic and fluorimetric methods. Morphologic analysis of the interaction between activated nonimmune macrophages (AM) and tumor cells attests to close cell-to-cell contact as an important factor in the mediation of target cell damage. All evidence suggests that damaged targets progressively disintegrate, and residues of target cell cytoplasma and/or nucleus are then engulfed as a secondary event. Analysis by impulse cytophotometry of the alterations in the DNA distribution occurring during interaction with AM revealed a marked decrease in the number of nuclei with higher DNA content. This effect was virtually identical irrespective of whether target cells were derived from normal or transformed tissues. Analysis of the consequences of AM/target cell interaction by cytofluorimetry showed that a large proportion of tumor cells lyse in the course of the interaction. However, no such killing occurred in recent explants derived from normal tissues interacted with AM; the majority of these targets were arrested in G1.
Insights
Activated nonimmune macrophages (AM) damage tumor cells through direct contact, causing disintegration and DNA content reduction. Normal cells, however, are arrested in G1 phase, indicating specific targeting mechanisms by macrophages.
Area of Science:
- Cell Biology
- Immunology
- Cancer Research
Background:
- Macrophages influence eukaryotic cell proliferation and viability through soluble factors.
- Macrophage-mediated target cell destruction was previously thought to be tumor-specific.
Purpose of the Study:
- To investigate the mechanisms of macrophage-mediated target cell damage.
- To differentiate the effects of activated nonimmune macrophages (AM) on tumor cells versus normal cells.
Main Methods:
- Morphological analysis of macrophage-target cell interactions.
- Impulse cytophotometry to assess DNA distribution.
- Cytofluorimetry to analyze cell viability and cell cycle progression.
Main Results:
- Close cell-to-cell contact is crucial for AM-induced target cell damage, leading to disintegration and engulfment.
- AM interaction significantly reduces the number of nuclei with higher DNA content in target cells, regardless of normal or transformed origin.
- Tumor cells undergo lysis upon AM interaction, while normal cells are primarily arrested in the G1 phase of the cell cycle.
Conclusions:
- Activated nonimmune macrophages induce significant damage and lysis in tumor cells via direct contact.
- Normal cells exhibit differential responses, with G1 arrest instead of lysis, suggesting specific interactions.
- Macrophage-mediated effects on target cells are not exclusively tumor-specific but show distinct outcomes based on cell type.