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Phagocytosis by human macrophages is accompanied by changes in ionic channel currents
C Ince1, J M Coremans, D L Ypey
1Department of Infectious Diseases, University Hospital, Leiden, The Netherlands.
Abstract:
The present study has shown that changes in ionic channel currents accompany the phagocytosis of particles by mononuclear phagocytes. The patch-clamp technique in the cell-attached configuration was applied to human monocyte-derived macrophages to measure the activity of single transmembrane ionic channels in intact cells. During such measurements, IgG-opsonized and non-opsonized latex particles were offered for phagocytosis under continuous video-microscopical observation. Single particles were presented to the phagocytes at a membrane location some distance from that of the patch electrode. After a lag period following particle attachment, enhanced inward and outward time-variant single channel currents coinciding with particle engulfment were observed. On the basis of current-voltage characteristics and membrane potential measurements, the outward-directed channels were identified as K+ channels. Phagocytosis was also accompanied by slow transient changes in background membrane currents, probably due to changes in the membrane potential of the phagocytosing cell. Phagocytosis of IgG-coated latex particles differed from phagocytosis of uncoated or albumin-coated particles by a shorter lag time between particle attachment and the onset of enhanced ionic channel activity.
Insights
Changes in ionic channel currents, particularly potassium (K+) channels, occur during phagocytosis by mononuclear phagocytes. This process involves particle engulfment and membrane potential shifts, with faster activity for IgG-coated particles.
Area of Science:
- Cell Biology
- Immunology
- Biophysics
Background:
- Mononuclear phagocytes play a crucial role in the immune system.
- Phagocytosis is a fundamental cellular process for particle clearance and immune response.
- Ionic channels are critical for regulating cell function and membrane potential.
Purpose of the Study:
- To investigate the involvement of ionic channel activity during phagocytosis by human macrophages.
- To characterize the types of ionic channels involved and their behavior during particle engulfment.
- To determine if opsonization affects the ionic channel response during phagocytosis.
Main Methods:
- Utilized the patch-clamp technique in the cell-attached configuration on human monocyte-derived macrophages.
- Measured single transmembrane ionic channel activity in intact cells.
- Observed phagocytosis of IgG-opsonized and non-opsonized latex particles using video-microscopy.
Main Results:
- Phagocytosis was accompanied by enhanced inward and outward time-variant single ionic channel currents during particle engulfment.
- Outward-directed channels were identified as potassium (K+) channels based on current-voltage characteristics.
- Phagocytosis of IgG-coated particles showed a shorter lag time before enhanced ionic channel activity compared to uncoated particles.
Conclusions:
- Ionic channel currents, specifically K+ channels, are dynamically altered during phagocytosis by mononuclear phagocytes.
- Phagocytosis induces changes in membrane potential, evidenced by altered background membrane currents.
- IgG opsonization accelerates the ionic channel response during phagocytosis, suggesting a role in modulating immune cell function.