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Isolation and In Vitro Culture of Murine and Human Alveolar Macrophages
Published on: April 20, 2018
The ultrastructure of mouse lung: the alveolar macrophage
Abstract:
Free alveolar macrophages of normal mouse lung have been studied in the electron microscope. The tissue was obtained from several young adult white mice. One other animal was instilled intranasally with diluted India ink 1(1/2) hours prior to the removal of the lung. Thin sections of the osmium-fixed, methacrylate-embedded tissue were examined either in an RCA EMU 2 electron microscope or in a Siemens and Halske Elmiskop I b. A few thick sections obtained from the same embeddings were stained for iron. The normal alveolar macrophages, which are usually in contact with the alveolar epithelium, were found to contain a variety of inclusion bodies, along with the usual cytoplasmic components like mitochondria, endoplasmic reticulum, and Palade granules. Another typical component of the cytoplasm of these cells which appears as small ( approximately 6 mmicro) very dense granules of composite fine structure is interpreted as ferritin. It is assumed that this ferritin is formed from red blood cells ingested by the alveolar macrophages. The macrophages in the alveoli were found to phagocytize intranasally instilled India ink particles. Such cells, with engulfed India ink particles, were often of more rounded form and the particles were frequently seen lying inside membrane-bound vacuoles or vesicles of the cytoplasm. The membrane of a few vesicles containing India ink particles was seen as the invaginated portion of the cell plasma membrane, and in one instance these same vesicles were seemingly interconnected with a rough surfaced cisterna of the endoplasmic reticulum. The process of phagocytosis is recognized as related to the "normal" process of pinocytosis.
Insights
Free alveolar macrophages in mouse lungs engulf India ink particles and contain ferritin, likely from ingested red blood cells. This phagocytosis process resembles pinocytosis.
Area of Science:
- Cell Biology
- Pulmonary Medicine
- Immunology
Background:
- Alveolar macrophages are crucial immune cells in the lung's defense system.
- Understanding their function, including phagocytosis, is vital for respiratory health.
Purpose of the Study:
- To investigate the ultrastructure and phagocytic activity of normal mouse alveolar macrophages.
- To identify inclusion bodies and understand the mechanism of particle uptake.
Main Methods:
- Electron microscopy was used to examine thin sections of mouse lung tissue.
- India ink was instilled intranasally to study phagocytosis.
- Iron staining was performed on thick sections.
Main Results:
- Normal alveolar macrophages contain various inclusion bodies, including ferritin, presumed to originate from ingested red blood cells.
- Macrophages actively phagocytize India ink particles, often within membrane-bound vesicles.
- The phagocytosis process appears related to pinocytosis, with vesicle membranes potentially originating from the plasma membrane and endoplasmic reticulum.
Conclusions:
- Mouse alveolar macrophages exhibit significant phagocytic capabilities for foreign particles.
- Ferritin within macrophages suggests a role in processing cellular debris, possibly from red blood cells.
- The study provides insights into the cellular mechanisms of phagocytosis and pinocytosis in lung macrophages.
