The significance of fibronectin in pneumonias was studied. The conclusions were as followes:
1) Plasma fibronectin in healthy subjects was measured 320±69μg/ml. The value was decreased to 210±45μg/ml in moderately advanced bacterial pneumonia and further to 102±50μg ml in the far advanced cases. With respect to the clinical course of the pneumonia patients, the values in surviving cases transiently decreased to about 200μg/ml at the most active phase of pneumonic inflammation, they then gradually increased to the normal level as the patient recovered. However, the values in deceased cases significantly dropped to the minimum level of 100μg/ml, and the patients cases were died of pneumonia within several days.
In the experimental rabbit pneumonia with E. coli inoculation, plasma fibronectin also decreased with the advancement of pneumonic lesions.
Based on these observations, plasma fibronectin appears to have some significant relation to the severity and the prognosis of pneumonia. Plasma fibronectin may therfore become one of the useful diagnostic markers to determine the severity of pneumonia and predict patient prognosis.
2) From the observations by immuno-enzyme method in experimental pneumonia, fibronectin was significantly localized on inflammatory sites in lung tissue, paticulary in the exudative fluid, inflammatory cells and swollen alveolar walls. On the other hand, fibronectin was not so dominant in normal tissue. Fibronectin may be consumed at pneumonic lesions thereby reducing plasma fibronectin in a pneumonic state.
3) Fibronectin was in vitro proteolytically degraded to “treated fibronectin” by releasing products from PMNs. The adhesion of PMNs to treated fibronectin was stronger than that to native fibronectin.
The adhesiveness of S. pneumoniae and K. pneumoniae, potentially the causative organisms of primary pneumonia, to treated fibronectin was very weak. However, the adhesiveness of H. influenzae, S. aureus and P. aeruginosa, frequent pathogens in secondary pneumonia, was much stronger. These reuslts suggested that fibronectin bears some relation with the occurence of bacterial pneumonia and acts as a host defence agent.