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[Efficacy of fibronectin on opsonic activity by alveolar macrophage and experimental rat pneumonia]
1Department of Internal Medicine, Nagasaki Rosai Hospital.
Abstract:
The opsonic activity of plasma fibronectin (FN) by rat alveolar macrophage (AM) was examined, and the in vivo effect of FN in Staphylococcus aureus (S. aureus) experimental rat pneumonia was evaluated. The chemiluminescence response of AM was enhanced by the presence of FN (300 micrograms/ml) in S. aureus and Streptococcus pneumoniae, but was not enhanced in gram-negative rods (Haemophilus influenzae, Branhamella catarrhalis, Pseudomonas aeruginosa). FN (300 micrograms/ml) promoted the phagocytosis of S. aureus by AM, but did not promote the bactericidal activity of that by AM. In the experimental rat pneumonia with S. aureus inoculation, plasma FN concentration decreased with time, but increased by the administration of FN (1 mg). The number of bacteria in the lung, peripheral white blood cell and BAL fluid cell also decreased by the administration of FN. Furthermore, FN was significantly improved on inflammatory findings of rat lung tissue 24 hours after inoculation with S. aureus. These results suggest that FN plays an important role as an opsonic by alveolar macrophage, and that FN has utility for clinical trials in patients with pneumonia.
Insights
Plasma fibronectin (FN) enhances the ability of alveolar macrophages to engulf Staphylococcus aureus. Administering FN reduced bacterial load and lung inflammation in a rat pneumonia model, suggesting its clinical potential.
Area of Science:
- Immunology
- Pulmonology
- Microbiology
Context:
- Alveolar macrophages (AM) are critical immune cells in the lungs.
- Plasma fibronectin (FN) is a key protein involved in immune responses.
- Bacterial pneumonia remains a significant global health concern.
Purpose:
- To investigate the opsonic activity of plasma fibronectin (FN) on rat alveolar macrophages (AM).
- To evaluate the in vivo efficacy of FN in a Staphylococcus aureus (S. aureus) experimental rat pneumonia model.
Summary:
- FN significantly enhanced the chemiluminescence response and phagocytosis of S. aureus by AM, but not gram-negative bacteria.
- In vivo, FN administration reduced bacterial load, inflammatory cell counts, and improved lung tissue inflammatory findings in S. aureus pneumonia.
- Plasma FN levels decreased during infection but were restored with FN treatment.
Impact:
- These findings highlight FN's crucial role as an opsonin for AM against S. aureus.
- The study suggests FN's therapeutic potential for treating bacterial pneumonia in clinical settings.