Efficacy of fibronectin on opsonic activity by alveolar macrophage and experimental rat pneumonia

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.