Lung inflammation induced by complement-derived chemotactic fragments in the alveolus

Area of Science:

• Pulmonary Medicine
• Immunology
• Pathology

Background:

• Chemotactic substances play a role in initiating inflammatory responses.
• Neutrophils are key mediators in acute inflammation.

Purpose of the Study:

• To investigate the role of C5-derived chemotactic fragments (C5fr) in inducing acute pulmonary inflammation.
• To determine the necessity of neutrophils and C5fr in this inflammatory process.

Main Methods:

• Intratracheal injection of C5fr into rabbits.
• Experimental depletion of circulating pulmonary neutrophils.
• Absorption of C5fr using immobilized antibody to human C5a.
• Examination of lung tissue using transmission and scanning electron microscopy.

Main Results:

• C5fr injection caused acute pulmonary inflammation with neutrophil, erythrocyte, and edema fluid accumulation.
• Neutrophil depletion or C5fr absorption prevented inflammation.
• Electron microscopy revealed neutrophil degranulation, fibrinoid deposits, and injury to pulmonary endothelium and type I epithelial cells.
• Endothelial and epithelial damage correlated with adjacent neutrophils.

Conclusions:

• C5fr initiates acute pulmonary inflammation requiring neutrophil recruitment.
• Intra-alveolar C5fr accumulation can lead to significant lung injury, including endothelial and epithelial damage.
• Pulmonary neutrophils are critical in mediating C5fr-induced lung inflammation and injury.