medwireNews: The proinflammatory cytokine interleukin (IL)-17A is upregulated in pleural inflammation of bacterial origin and may be valuable as a diagnostic marker, study results indicate.
The findings are reported in Respirology by Ioannis Kalomenidis (National and Kapodistrian University of Athens, Haidari, Greece) and colleagues, who examined the role of IL-17A in a series of clinical and animal studies.
They began by measuring IL-17A expression in 84 patients with pleural effusions (PEs) of various etiologies. The cytokine was upregulated in several conditions, including in 62% of patients with pneumonia and in 40% of those with tuberculosis. It was less frequently upregulated in PEs of malignant (9%) or other etiologies (16%). Also, IL-17A was more often detected in the pleural fluid (32%) than in serum samples (10%).
In the same cohort, Kalomenidis measured levels of other markers of acute pleural inflammation, finding significant correlations between IL-17A and neutrophils, lactate dehydrogenase, glucose, pH, interleukin-8, and vascular endothelial growth factor.
The team then studied 92 patients with neutrophil-predominant PEs of various etiologies. In this cohort, IL-17A was upregulated in 46% of patients with pneumonia but in no other etiologic subtype.
Finally, the researchers injected IL-17A directly into the pleural space in mice. This resulted in a significant increase in pleural neutrophils at 4 and 24 hours post-injection, they report.
Furthermore, injection of anti-IL-17A neutralizing antibodies attenuated the inflammatory response to E. coli-derived lipopolysaccharide at 4 and 24 hours and to Staphylococcus aureus-induced pleural neutrophilia at 4 hours.
Kalomenidis and team conclude: "The central and novel message is the close association between IL-17A and pleural inflammation due to bacterial infection.
"The above findings suggest that IL-17A might be clinically useful as a diagnostic marker for parapneumonic pleural effusions and that IL-17A plays an important role in the pathobiology of infection-related pleural inflammation."
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