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Changes in neutrophil actin and shape during sequestration induced by complement fragments in rabbits
H Motosugi1, L Graham, T W Noblitt
1Herman B. Wells Center for Pediatric Research, Indiana University Medical Center, Indianapolis, USA.
The American Journal of Pathology
|September 1, 1996
Summary
Complement fragments rapidly alter neutrophil actin distribution, causing them to become rounder and less deformable. This change in neutrophil shape may explain their sequestration in lung capillaries.
Area of Science:
- Immunology
- Cell Biology
- Pulmonary Medicine
Background:
- Neutrophil sequestration in lung capillaries is linked to complement fragments.
- Decreased neutrophil deformability may prolong lung capillary transit times.
- Cytoskeletal protein alterations are implicated in changes to neutrophil deformability.
Purpose of the Study:
- To investigate if complement fragments alter actin distribution in neutrophils within lung capillaries.
- To determine if sequestered neutrophils exhibit reduced deformability.
Main Methods:
- Rabbit lungs were infused with complement fragments or saline.
- Ultrathin cryosections of lung tissue were immunolabeled for actin.
- Quantification of gold particles associated with actin in neutrophil regions.
- Evaluation of neutrophil shape using laser confocal microscopy.
Main Results:
- Complement fragments induced a significant increase in the ratio of submembrane/central actin.
- The number of actin-associated gold particles per microvillus increased in complement-treated rabbits.
- Neutrophils became more spherical shortly after complement fragment infusion, suggesting rapid shape changes.
Conclusions:
- Intravascular complement fragments rapidly redistribute neutrophil actin towards the submembrane region and microvilli.
- This actin redistribution likely reduces neutrophil deformability by altering cell stiffness and microvillus function.
- The findings suggest a mechanism for complement-induced neutrophil sequestration in the lungs.