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Further cytological observation on 'activation' by superimposed antigen of inflammation-mediated macrophages
Abstract:
Compact cell aggregates were induced by an injection of a superimposed antigen, sheep erythrocytes (SRBC) into PSK (a protein-bound polysaccharide)-'prepared' mouse footpad. Major cell types in the cell aggregate were macrophages which rapidly digested superimposed SRBC but not PSK substances which were retained over seven days within their phagosomes. Macrophages without PSK like substances-containing phagosomes occurred invariably outside the cell aggregate. The macrophages in the cell aggregate were interlocked via their cytoplasmic projections. Ruthenium red, a specific dye for extracellular proteoglycans, clearly revealed their surface coats and also closely contacted zones of adjoining macrophages. The surface coats were not uniform in distribution and became sporadically thickened deposits at invaginations of the plasma membrane. Ladder-like structures among adjacent cytoplasmic projections also showed a strong affinity to the dye. It is suggested that a primary function of these structures is the maintenance of close contact of aggregating macrophages. Another observation was that binucleate macrophages occurred in the cell aggregates. Careful inspection on sections of well-preserved tissues concludes that such cells were not formed by a cell fusion between mononucleate macrophages in the cell aggregates. Formation of such a binucleate cell from the macrophage in the aggregates is also discussed.
Insights
Macrophages aggregate and interlock via cytoplasmic projections after sheep erythrocytes (SRBC) injection. These cells retain protein-bound polysaccharide (PSK) substances, suggesting a role in immune response and cell-cell communication.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Immune responses involve complex cellular interactions.
- Macrophages play a critical role in antigen processing and immune regulation.
- Protein-bound polysaccharide (PSK) is known to modulate immune responses.
Purpose of the Study:
- To investigate the cellular mechanisms of macrophage aggregation induced by SRBC in PSK-prepared mice.
- To characterize the ultrastructure and composition of macrophage aggregates.
- To explore the origin of binucleate macrophages within these aggregates.
Main Methods:
- Induction of cell aggregates via sheep erythrocytes (SRBC) injection in PSK-prepared mouse footpads.
- Electron microscopy and ruthenium red staining to visualize cell structures and extracellular matrix.
- Histological analysis of macrophage morphology and interactions.
Main Results:
- Compact macrophage aggregates formed, with macrophages interlocking via cytoplasmic projections.
- Macrophages rapidly digested SRBC but retained PSK substances in phagosomes for over seven days.
- Ruthenium red staining revealed surface coats and ladder-like structures between macrophages, suggesting roles in adhesion.
- Binucleate macrophages were observed within aggregates, not formed by cell fusion.
Conclusions:
- Macrophage aggregation involves specific structural adaptations for cell-cell contact and antigen processing.
- PSK substances are retained within macrophages, potentially influencing their function and longevity.
- The observed structures likely maintain macrophage aggregate integrity, and binucleate cells may arise through alternative mechanisms.