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Electron microscopic analysis of the normal and the activated pleural macrophage
M H Baumann1, K Heinrich, S A Sahn
1Division of Pulmonary and Critical Care Medicine, Medical University of South Carolina, Charleston 29425.
Abstract:
Despite an apparent role in pleural pathophysiology, little information is known about pleural macrophage morphology. Intrapleural tetracycline (TCN) results in pleural macrophage influx and pleural fibrosis; intrapleural carrageenan (CAR) induces macrophage influx without ensuing fibrosis. Pleural macrophages collected from normal (NL) and TCN- or CAR-exposed rabbit pleural spaces were examined with electron microscopy. Cellular size; number of microvilli; pseudopods; coated pits (CP) and coated vesicles (CV); and prevalence of golgi, rough endoplasmic reticulum (RER), and intermediate filaments (IF) were determined. The means of each variable in each group were assessed by one-way analysis of variance, with post hoc testing performed by Scheffe F test; p < or = .05 was considered significant. TCN-stimulated pleural macrophages were characterized by their small perimeters. CAR-induced pleural macrophages were marked by their large size and abundant intracellular amorphous material. They had larger perimeters, areas, and diameters than the TCN-induced or normal macrophages and thus smaller numbers of CV + CP per area. The normal pleural macrophages were characterized by more IF, microvilli, and microvilli per perimeter than either the CAR- or TCN-induced pleural macrophages. No differences between groups were found in nuclear cytoplasmic ratios, number of pseudopods, and content of golgi or of RER. The results suggest that normal pleural macrophages and TCN- and CAR-induced pleural macrophages differ morphologically and that these morphologic differences reflect functional differences.
Insights
Pleural macrophages exhibit distinct morphological differences based on exposure to tetracycline (TCN) or carrageenan (CAR), suggesting varied functions in pleural pathophysiology. These cellular variations are key to understanding pleural inflammation and fibrosis.
Area of Science:
- Pulmonary and Pleural Pathophysiology
- Cellular Biology
- Immunology
Background:
- Pleural macrophage morphology is poorly understood despite its role in pleural diseases.
- Intrapleural tetracycline (TCN) induces pleural fibrosis, while carrageenan (CAR) causes macrophage influx without fibrosis.
Purpose of the Study:
- To investigate and compare the ultrastructural morphology of pleural macrophages from normal rabbits and those exposed to TCN or CAR.
- To correlate observed morphological differences with potential functional variations in pleural macrophages.
Main Methods:
- Pleural macrophages were collected from normal (NL), TCN-exposed, and CAR-exposed rabbits.
- Electron microscopy was used to analyze cellular size, surface features (microvilli, pseudopods), internal structures (coated pits/vesicles, Golgi, RER), and intermediate filaments (IF).
- Statistical analysis (ANOVA, Scheffe F test) was performed to determine significant differences between groups (p < .05).
Main Results:
- TCN-stimulated macrophages were smaller with distinct features.
- CAR-induced macrophages were larger, containing abundant amorphous material, and had fewer coated vesicles/pits per area.
- Normal macrophages exhibited more intermediate filaments and microvilli compared to TCN- or CAR-induced macrophages.
Conclusions:
- Normal, TCN-induced, and CAR-induced pleural macrophages display significant morphological differences.
- These distinct morphologies suggest underlying functional variations relevant to pleural inflammation and fibrosis development.