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Updated: Aug 1, 2026
Isolation of Mouse Peritoneal Cavity Cells
Published on: January 29, 2010
A stereological ultrastructural study of stimulated peritoneal macrophages in the germ-free mouse
Abstract:
Peritoneal macrophage ultrastructure was analysed stereologically in germ-free mice given a single intraperitoneal injection of sterile, pyrogen-free saline. Thus the stimulant was non-particulate, non-antigenic and inorganic, and effects of immune reactions were minimal. Macrophages were recovered 1, 6, 24 and 72 h after stimulation. A sequence of structural alterations is reported which may be fundamental to macrophage activation. The plasma membrane and nuclear envelope increased in area within only 1 h of saline injection. During the next 5 h loss of plasma membrane, probably by pinocytosis, caused cellular "rounding" and clear-cut alteration in surface configuration. At the same time lysosome-like granules enlarged but decreased in number. By 24 h most cellular structures and compartments (including the plasma membrane) were enlarged. Morphological evidence of nuclear activation accompanied a rather modest enlargement of the nucleus at this stage. The RER hypertrophied last and must, therefore, be judged sufficient in resident macrophages to support the initial growth response which results after stimulation. Thus hypertrophy was observed eventually in every structure examined. Even the minimally activated macrophages resident in the peritoneum of germ-free mice respond readily to stimulation.
Insights
Sterile saline injection activates peritoneal macrophages in mice, causing rapid structural changes like membrane enlargement and cell rounding. These minimally activated macrophages show significant ultrastructural alterations following stimulation.
Area of Science:
- Immunology
- Cell Biology
- Stereology
Background:
- Peritoneal macrophages are key immune cells.
- Understanding macrophage activation is crucial for immunology.
- Minimal stimulation models are needed to study fundamental activation processes.
Purpose of the Study:
- To investigate the ultrastructural changes in peritoneal macrophages following non-specific stimulation.
- To identify the sequence of cellular events during macrophage activation.
Main Methods:
- Stereological analysis of peritoneal macrophage ultrastructure.
- Germ-free mice model.
- Intraperitoneal injection of sterile saline as a non-particulate, non-antigenic stimulant.
- Macrophage recovery at 1, 6, 24, and 72 hours post-injection.
Main Results:
- Rapid increase in plasma membrane and nuclear envelope area within 1 hour.
- Cellular rounding and surface configuration changes due to plasma membrane loss (pinocytosis) within 6 hours.
- Enlargement and decreased number of lysosome-like granules.
- General enlargement of cellular structures and compartments by 24 hours.
- Evidence of nuclear activation and RER (Rough Endoplasmic Reticulum) hypertrophy observed later.
- All examined cellular structures eventually showed hypertrophy.
Conclusions:
- Macrophage activation involves a sequential series of ultrastructural alterations.
- Even minimally activated resident macrophages exhibit a robust response to stimulation.
- The observed changes suggest a fundamental mechanism of macrophage activation.
