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Published on: December 26, 2017
Effects of intravenous silica on immune and non-immune functions of the murine host
Abstract:
Silica, an agent toxic for macrophages, administered i.v. to DBA/2 mice rapidly depresses the clearance of colloidal carbon by the reticuloendothelial system and reduces the in vitro phagocytic activity of peritoneal macrophages harvested 3 days after silica injection. Silica blocks the humoral immune response to sheep erythrocytes and the cell-mediated immune response to allogeneic fibroblasts when given before antigen. Silica also induces complex alterations in spleen cell responsiveness to concanavalin A involving both local and serum factors. Silica had no significant effect on the induction of interferon by statolon or Newcastle disease virus. No unequivocal evidence was obtained that silica has a direct depressive effect on cells other that macrophages, but indirect effects on lymphocytes were produced most likely by factors released from silica-lysed macrophages. Intravenous silica may prove useful for the separation of interferon induction and immune response stimulation in studies of host resistance to infection and oncogenesis. Considerable variation exists in the immunodepressive effects of different preparations of silica.
Insights
Intravenous silica administration impairs macrophage function and suppresses immune responses in mice. These effects, primarily on macrophages, suggest silica
Area of Science:
- Immunology
- Toxicology
- Cell Biology
Background:
- Macrophages play a crucial role in immune surveillance and clearance.
- Silica is known to affect macrophage function.
- Understanding silica's impact on the immune system is vital for various research applications.
Purpose of the Study:
- To investigate the effects of intravenous silica administration on macrophage activity and immune responses in DBA/2 mice.
- To determine if silica affects humoral and cell-mediated immunity.
- To explore the potential of silica in separating immune response pathways.
Main Methods:
- Intravenous administration of silica to DBA/2 mice.
- Assessment of colloidal carbon clearance by the reticuloendothelial system.
- In vitro phagocytic activity assays of peritoneal macrophages.
- Evaluation of immune responses to sheep erythrocytes and allogeneic fibroblasts.
- Analysis of spleen cell responsiveness to concanavalin A.
Main Results:
- Silica rapidly depressed reticuloendothelial system clearance and macrophage phagocytic activity.
- Silica administration before antigen blocked both humoral and cell-mediated immune responses.
- Complex alterations in spleen cell responsiveness were observed, involving local and serum factors.
- No significant effect on interferon induction was noted.
- Indirect effects on lymphocytes were likely mediated by factors from silica-lysed macrophages.
Conclusions:
- Intravenous silica primarily affects macrophages, leading to suppressed immune functions.
- Silica's immunodepressive properties are dose- and preparation-dependent.
- Silica may be a valuable tool for dissecting immune response pathways in host resistance studies.
- Further research is needed to fully elucidate the mechanisms of silica-induced immunomodulation.
