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Membrane capacitance changes associated with particle uptake during phagocytosis in macrophages
1Department of Pharmacological and Physiological Sciences, The University of Chicago, Chicago, Illinois 60637, USA.
Biophysical Journal
|October 28, 1998
Summary
Capacitance measurements effectively monitor particle uptake by macrophages during phagocytosis. This technique reveals changes in cell capacitance linked to the ingestion of immune complexes and latex particles, offering insights into cellular processes.
Area of Science:
- Cell Biology
- Biophysics
- Immunology
Background:
- Phagocytosis is a critical cellular process for immune defense and cellular homeostasis.
- Monitoring phagocytosis in real-time is essential for understanding cellular responses to pathogens and particles.
- Existing methods for studying phagocytosis can be complex and may not provide continuous, dynamic measurements.
Purpose of the Study:
- To establish capacitance measurements as a method for monitoring particle uptake in macrophages.
- To investigate the relationship between particle size and the changes in cell capacitance during phagocytosis.
- To differentiate particle uptake from other cellular processes like exocytosis using capacitance changes.
Main Methods:
- Utilized capacitance measurements to assess particle uptake in human monocyte-derived macrophages (HMDMs) and J774.1 cells.
- Exposed cells to immune complexes and sized latex particles (0.8 and 3.2 microns).
- Inhibited particle uptake using cytochalasin B and used platelet-activating factor as a soluble stimulus control.
Main Results:
- Observed an average decrease of 8 pF in cell capacitance upon exposure to immune complexes.
- Particle uptake inhibition resulted in a minimal capacitance change (0.5 pF), while soluble stimuli caused no change.
- Stepwise capacitance decreases of 250 fF for 0.8-micron and 480 fF for 3.2-micron particles were recorded.
- Discrepancies between measured and predicted step sizes for smaller particles suggest potential lower limits for phagocytic vacuole size or multiple particle engulfment.
Conclusions:
- Capacitance measurements provide a sensitive and dynamic method for quantifying particle uptake during phagocytosis.
- The technique can distinguish between particulate and soluble stimuli, confirming its specificity for phagocytosis.
- Observed biphasic capacitance changes indicate dynamic interactions between phagocytosis and exocytosis in macrophages.