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Comparison of lavaged and intrapulmonary alveolar macrophages in respect to lysozyme content and size in the rat
Abstract:
Lavaged and in situ rat alveolar macrophages were compared with respect to lysozyme content and size in order to assess the extent to which macrophages from pulmonary lavages reflect the in situ cell population. This relationship was studied in normal rats and in rats with pulmonary granulomas induced by glucan stimulation (10 mg/kg given intravenously on Days 5, 3, and 1 before being killed). Alveolar macrophages in pulmonary lavages and histologic sections were stained for lysozyme by the immunoperoxidase method using rabbit antiserum to rat lysozyme. Enzyme content and cell size were measured with a conventional scanning cytospectrophotometer and an automated image analysis system (LEYTAS). Scanning cytospectrophotometry measurements showed that 26% of in situ alveolar macrophages from glucan-treated rats contained more lysozyme than did control cells and that 31% possessed larger areas. Fewer large alveolar macrophages containing increased amounts of lysozyme were detected in lavages of glucan-treated rats. Frequency histograms of lysozyme content and cell size were similar for lavaged and in situ macrophages from control rats. Measurements with LEYTAS confirmed the results. These experiments demonstrate that alveolar macrophages obtained by lavage are representative of their in situ counterparts in normal but not in glucan-treated rats.
Insights
Pulmonary lavage accurately reflects normal rat alveolar macrophages but not those from glucan-induced granulomas. Macrophages in lavage underrepresented larger, lysozyme-rich cells in diseased lungs.
Area of Science:
- Immunology
- Cell Biology
- Pulmonary Research
Background:
- Alveolar macrophages are crucial for lung immunity.
- Pulmonary lavage is a common method to obtain these cells.
- Assessing lavage accuracy is vital for research.
Purpose of the Study:
- To compare lavaged and in situ rat alveolar macrophages.
- To evaluate lysozyme content and cell size.
- To determine if lavage reflects the in situ population in normal and diseased states.
Main Methods:
- Rats were treated with glucan to induce pulmonary granulomas.
- Alveolar macrophages were obtained via lavage and from histologic sections (in situ).
- Lysozyme content and cell size were measured using immunoperoxidase staining, scanning cytospectrophotometry, and automated image analysis (LEYTAS).
Main Results:
- In normal rats, lavaged and in situ macrophages showed similar lysozyme content and size.
- In glucan-treated rats, 26% of in situ macrophages had higher lysozyme and 31% had larger areas compared to controls.
- Lavages from glucan-treated rats underrepresented these larger, lysozyme-rich macrophages.
Conclusions:
- Alveolar macrophages obtained by lavage are representative of in situ cells in normal rats.
- Pulmonary lavage does not accurately reflect the in situ alveolar macrophage population in glucan-induced granulomas.
- Glucan stimulation alters macrophage characteristics, impacting lavage representativeness.