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Deficient phagocytosis secondary to breakdown of opsonic factors in infected exudates
Abstract:
Pleural empyema, a clinical entity characterized by the simultaneous presence of large number of PMNLs and viable bacteria, is a biological paradox which has not been fully explained yet. Our preliminary studies suggest that receptor and bactericidal functions of PMNL isolated from purulent exudates, can be close to normal in this condition. Supernatants of these empyemas however have been shown to be low in heat labile opsonic activity and complement hemolytic activity. These observations have been extended by the demonstration of breakdown of IgG, C3 and factor B in infected pleural effusions as opposed to pleural fluids obtained under other conditions. The breakdown of Ig and C3 seems to be enzymatic and to occur, at least for C3, even in the absence of Ca and Mg ions: thus, direct cleavage of C3, possibly by PMNL enzymes, has to be postulated to explain these results. Present work in our laboratory is trying to explore this possibility.
Insights
Pleural empyema involves high white blood cell (PMNL) and bacteria counts. Despite normal PMNL function, low opsonic activity and complement breakdown suggest enzymatic degradation of immune components in empyema fluid.
Area of Science:
- Immunology
- Microbiology
- Pulmonology
Background:
- Pleural empyema presents a paradox with numerous neutrophils (PMNLs) and bacteria.
- PMNLs from empyema exudates show near-normal function.
- Empyema fluid supernatants exhibit reduced opsonic and hemolytic complement activity.
Purpose of the Study:
- To investigate the mechanisms behind the paradoxical nature of pleural empyema.
- To further characterize the immune environment within infected pleural effusions.
Main Methods:
- Analysis of PMNL function in purulent exudates.
- Assay of heat-labile opsonic activity and complement hemolytic activity in empyema supernatants.
- Demonstration of immunoglobulin (IgG) and complement component (C3, Factor B) breakdown in infected pleural effusions.
Main Results:
- PMNLs from empyema exudates exhibit normal receptor and bactericidal functions.
- Infected pleural effusions show breakdown of IgG, C3, and Factor B.
- Complement component breakdown occurs even without calcium and magnesium ions, suggesting direct enzymatic cleavage.
Conclusions:
- The breakdown of immune components, particularly C3, may be mediated by enzymes, potentially from PMNLs.
- Further research is needed to confirm the role of PMNL enzymes in C3 cleavage within pleural empyema.
- This enzymatic breakdown could explain the impaired immune response despite high PMNL counts in pleural empyema.