title: Low levels of functional of alpha 1-proteinase inhibitor in the promotion of C3-cleavage by granulocyte-neutral proteases in pleural empyema.
abstract: It has been suggested that C3 breakdown by granulocyte-neutral proteases in pleural empyemas may be related to a decreased inhibitor potential for these enzymes. In the present study it was shown that in 17 infected pleural effusions, high proteolytic activity on 125I-labeled C3 (16.3% +/- 4.4%) correlated with low functional levels of alpha 1-proteinase inhibitor (alpha 1-PI), as determined by trypsin-inhibitory capacity (56.2 +/- 20.1 IU/ml; rs = -0.97, P less than .001), whereas in 18 sterile pleural effusions there was no such correlation (125I-labeled C3 cleavage, 2.2% +/- .2%; trypsin-inhibitory capacity, 192.6 +/- 26.7 IU/ml). However, alpha 1-PI and alpha 2-macroglobulin protein concentrations in infected and sterile effusions (as measured by immunodiffusion) were similar. Fifteen strains of three bacterial species--Streptococcus pneumoniae, Pseudomonas aeruginosa, and Proteus mirabilis--isolated from patients with pneumonia or empyema inactivated the elastase-inhibitory capacity of alpha 1-PI in vitro. These results show that in empyemas functional levels of alpha 1-PI were too low to inactivate granulocyte elastase and that some bacterial species may contribute to the low inhibitor potential of infected pleural fluid by direct alpha 1-PI inactivation.
mesh_terms: D001798:Blood Proteins / Q000378:metabolism*; D003176:Complement C3 / Q000378:metabolism*; D004653:Empyema / Q000201:enzymology*; D010450:Endopeptidases / Q000097:blood*; D006098:Granulocytes / Q000201:enzymology*; D006801:Humans; D007122:Immunoelectrophoresis; D015260:Neprilysin; D010084:Oxidation-Reduction; D010196:Pancreatic Elastase / Q000037:antagonists & inhibitors; D010996:Pleural Effusion / Q000201:enzymology*; D011513:Proteus mirabilis / Q000502:physiology; D011550:Pseudomonas aeruginosa / Q000502:physiology; D013296:Streptococcus pneumoniae / Q000502:physiology; D000515:alpha 1-Antitrypsin; D000511:alpha-Macroglobulins / Q000378:metabolism
chemical_list: D001798:Blood Proteins; D003176:Complement C3; D000515:alpha 1-Antitrypsin; D000511:alpha-Macroglobulins; D010450:Endopeptidases; D010196:Pancreatic Elastase; D015260:Neprilysin