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Ligand-specific cross-inhibition of monocyte phagocytosis
1Third Department of Medicine, University Medical School of Debrecen, Hungary.
Abstract:
Human monocytes exposed to particles reacting with receptors of one specific type demonstrate a markedly reduced phagocytosis of particles reacting with receptors of another type. The phagocytosis of yeast particles (Saccharomyces cerevisiae) coated with C3 fragments and of uncoated ones by monocytes can inhibit the subsequent endocytosis of sheep erythrocytes sensitized with IgG antibody and vice versa. The erythrocytes were labelled with 51Cr and the yeast particles with 125I. The dependence of the receptor-ligand reaction on temperature and time of preincubation, as well as on ratio of cell and particle, suggests that this cross-inhibition may be associated with plasma membrane modulations beginning with the attachment of ligands to a receptor and followed by their endocytosis. The differences between the functions of temperature, time, and concentration in inhibition caused by different receptor-ligand reactions suggest that these membrane modulations are probably ligand-specific processes.
Insights
Monocyte phagocytosis is inhibited when cells encounter different particle types, suggesting specific cellular responses to various ligands. This cross-inhibition highlights ligand-specific plasma membrane modulations during particle uptake.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Monocytes are key immune cells responsible for phagocytosis.
- Phagocytosis involves the recognition and engulfment of particles by immune cells.
- Receptor-ligand interactions mediate cellular uptake processes.
Purpose of the Study:
- To investigate the phenomenon of cross-inhibition in monocyte phagocytosis.
- To explore the underlying mechanisms of receptor-mediated particle uptake.
- To determine if plasma membrane modulations are ligand-specific.
Main Methods:
- Human monocytes were exposed to yeast particles (Saccharomyces cerevisiae) and sheep erythrocytes.
- Yeast particles were coated with C3 fragments or left uncoated.
- Erythrocytes were sensitized with IgG antibody.
- Radiolabelling (51Cr for erythrocytes, 125I for yeast) was used to quantify phagocytosis.
- Experiments were conducted under varying temperature, time, and cell-particle ratios.
Main Results:
- Exposure to one particle type significantly reduced monocyte phagocytosis of a different particle type.
- Phagocytosis of C3-coated or uncoated yeast inhibited subsequent erythrocyte uptake, and vice versa.
- The observed cross-inhibition was dependent on temperature, preincubation time, and cell-particle ratio.
- These dependencies suggest plasma membrane modulations initiated by ligand-receptor attachment and followed by endocytosis.
Conclusions:
- Monocyte phagocytosis exhibits cross-inhibition between different particle types.
- This cross-inhibition is likely mediated by ligand-specific plasma membrane modulations.
- The findings provide insights into the complex regulation of cellular uptake mechanisms.