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Interleukin 6 activity in pleural effusion. Its diagnostic value and thrombopoietic activity
A Yokoyama1, M Maruyama, M Ito
1Second Department of Internal Medicine, Ehime University School of Medicine, Japan.
Insights
Interleukin 6 (IL-6) is elevated in pleural fluid, aiding in diagnosing effusions and indicating local production. Higher IL-6 levels in tuberculous effusions suggest its diagnostic utility.
Area of Science:
- Biochemistry
- Immunology
- Pulmonology
Background:
- Interleukin 6 (IL-6) is a cytokine implicated in various inflammatory and disease processes.
- Pleural effusions represent fluid accumulation in the pleural space, with diverse underlying causes.
Purpose of the Study:
- To investigate the role of IL-6 in the pathophysiology and diagnosis of pleural effusions.
- To compare IL-6 concentrations in different types of pleural effusions.
Main Methods:
- Measurement of IL-6 concentrations in pleural fluid using a specific functional bioassay.
- Comparison of IL-6 levels between exudative and transudative effusions.
- Analysis of IL-6 levels in tuberculous and malignant effusions.
- Correlation analysis with other biomarkers like lactate dehydrogenase (LDH), adenosine deaminase (ADA), C-reactive protein (CRP), and platelet counts.
Main Results:
- IL-6 levels were significantly higher in exudative effusions compared to transudative effusions.
- Tuberculous effusions showed significantly higher IL-6 concentrations than malignant effusions.
- Pleural IL-6 levels correlated positively with pleural LDH, pleural/serum LDH ratio, pleural ADA activity, serum CRP, and peripheral blood platelet counts.
- Pleural IL-6 levels were consistently higher than serum IL-6 levels, with a significant correlation between the two.
Conclusions:
- IL-6 is likely produced locally within the pleural space.
- Pleural IL-6 levels can serve as a valuable biomarker for the differential diagnosis of pleural effusions.
- Locally produced IL-6 may translocate into circulation, contributing to systemic effects like elevated CRP and thrombocytosis.
Abstract:
We measured interleukin 6 (IL-6) concentrations in the pleural fluid of various patients to determine its role in pathophysiology and diagnosis by using specific functional bioassay. IL-6 levels were significantly higher in exudate than in transudate (79.3 +/- 176.2 U/ml [n = 55] vs 1.7 +/- 1.8 U/ml [n = 12]; p < 0.01). Tuberculous effusion contained a significantly higher amount of IL-6 than malignant effusion (181.3 +/- 176.2 U/ml [n = 13] vs 29.4 +/- 71.5 U/ml [n = 29]; p < 0.005). Pleural IL-6 levels were invariably higher than serum IL-6 levels, and both were significantly correlated (n = 21, r = 0.632; p < 0.02). Pleural IL-6 levels were significantly correlated with lactate dehydrogenase (LDH) in pleural fluid (r = 0.392; p < 0.01), ratio of pleural/serum LDH (r = 0.571; p < 0.01), pleural adenosine deaminase activity (r = 0.599; p < 0.01), and serum C-reactive protein (r = 0.494; p < 0.01). Furthermore, IL-6 levels were significantly correlated with peripheral blood platelet counts (r = 0.447; p < 0.001). These results suggest that (1) IL-6 is produced locally in pleural space, (2) pleural IL-6 level is helpful for differential diagnosis, and (3) locally produced IL-6 could leak to circulation and cause systemic effects such as the induction of C-reactive protein and thrombocytosis.