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Endotoxin-induced size change in bone marrow progenitors of granulocytes and macrophages
Abstract:
Injection of 5 mug endotoxin to adult C57BL mice caused a marked increase in the sedimentation velocity of granulocytic and macrophage progenitor (colony-forming) cells in the bone marrow. This change was maximal two days after injection and was not accompanied by corresponding changes in total marrow nucleated cell populations. The endotoxin-induced shift was not dependent on the presence of the thymus but did not occur in mice challenged after preinjection with endotoxin. No changes in buoyant density, cell cycle status, pattern of differentiation and responsiveness of granulocytic and macrophage progenitor cells were observed after the injection of endotoxin. The increased sedimentation velocity of progenitor cells appears to indicate an increase in cell volume but the mechanisms involved have not been identified.
Insights
Endotoxin injection increased the size of bone marrow progenitor cells in mice, indicated by faster sedimentation. This endotoxin effect was temporary and did not alter cell differentiation or responsiveness.
Area of Science:
- Hematology
- Immunology
- Cell Biology
Background:
- Hematopoietic stem and progenitor cells (HSPCs) are crucial for blood cell formation.
- Endotoxins, components of bacterial cell walls, can trigger significant immune responses.
Purpose of the Study:
- To investigate the effects of endotoxin on the physical properties of myeloid progenitor cells.
- To determine if endotoxin influences cell size, density, or cell cycle status.
Main Methods:
- Adult C57BL mice were injected with endotoxin.
- Sedimentation velocity and buoyant density of bone marrow progenitor cells were analyzed.
- Cell cycle status, differentiation patterns, and responsiveness were assessed.
Main Results:
- Endotoxin injection markedly increased the sedimentation velocity of granulocytic and macrophage progenitor cells.
- This effect peaked at two days post-injection and was not linked to changes in total cell numbers.
- No alterations in cell density, cell cycle, differentiation, or responsiveness were observed.
Conclusions:
- Endotoxin induces a transient increase in myeloid progenitor cell volume.
- The underlying mechanisms for this volume change remain unidentified.
- The thymus is not required for this endotoxin-induced effect.