Related Experiment Videos
Morphological heterogeneity among fractionated alveolar macrophages in their release of lysosomal enzymes
1Department of Nutrition, School of Medicine, University of Tokushima, Japan.
Abstract:
When coupled with separation of alveolar macrophages (AM) into four different density fractions (I, II, III and IV) by discontinuous Percoll gradient centrifugation, ultrastructural heterogeneity was evident in secreting process of lysosomal enzymes. Lower dense AM (I and II) released high levels of acid phosphatase and cathepsin B, whereas higher dense ones (III and IV) did not. Ultrastructurally, there were multiple ruffling and active extension of long cytoplasmic processes from one pole or around the cell surface of AM obtained from the higher density fractions. In contrast, AM from lower dense fractions had much less cytoplasmic processes and contained more cytoplasmic vacuoles showing positive reactions of acid phosphatase. These cells featured more frequently round or ovoid knobs with acid phosphatase activity along and from the tips of the cytoplasmic processes, suggestive of exocytosis. It was suggested that these ultrastructural changes linked to the maturation process and release of lysosomal enzymes from differentiated AM.
Insights
Alveolar macrophages (AM) show distinct ultrastructural differences based on density. Lower density AM release more lysosomal enzymes, suggesting a link between cell structure and enzyme secretion during maturation.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Alveolar macrophages (AM) are crucial immune cells in the lungs.
- Lysosomal enzymes play a vital role in cellular processes and pathogen clearance.
- Understanding AM heterogeneity is key to deciphering lung immunity.
Purpose of the Study:
- To investigate the ultrastructural heterogeneity of alveolar macrophages (AM).
- To correlate AM density fractions with lysosomal enzyme secretion.
- To elucidate the relationship between AM ultrastructure and enzyme release.
Main Methods:
- Separation of AM into four density fractions (I-IV) using discontinuous Percoll gradient centrifugation.
- Ultrastructural analysis of AM from different density fractions.
- Assay of lysosomal enzyme activity (acid phosphatase, cathepsin B) in AM fractions.
Main Results:
- Significant ultrastructural differences were observed among AM density fractions.
- Lower density AM (I and II) exhibited higher secretion of acid phosphatase and cathepsin B.
- Higher density AM (III and IV) showed less enzyme secretion but distinct ruffled cytoplasmic processes, suggestive of exocytosis.
Conclusions:
- AM density correlates with ultrastructural characteristics and lysosomal enzyme secretion.
- Specific ultrastructural features in lower density AM indicate active exocytosis.
- These findings suggest a link between AM maturation, differentiation, and lysosomal enzyme release.