Circulating immunoreactive interleukin-6 in cystic fibrosis

Area of Science:

• Pulmonary Medicine
• Immunology
• Cystic Fibrosis Research

Background:

• Cystic fibrosis (CF) patients with chronic Pseudomonas aeruginosa infection experience pulmonary inflammation.
• Understanding inflammatory marker compartmentalization is crucial for managing CF exacerbations.

Purpose of the Study:

• To compare circulating and sputum concentrations of inflammatory markers, including interleukin-6 (IL-6), in CF patients.
• To assess the impact of antibiotic treatment on these markers during exacerbations and stable states.
• To evaluate IL-6 as a potential marker of inflammation in CF.

Main Methods:

• Measurement of IL-6, tumor necrosis factor-alpha, neutrophil elastase-alpha1-antiproteinase complex (NEAPC), and C-reactive protein (CRP) in serum and sputum.
• Analysis of samples from CF patients during exacerbation, post-antibiotic treatment, and stable periods.
• Comparison with healthy control subjects and correlation analysis with lung function (FEV1, FVC) and neutrophil elastase.

Main Results:

• IL-6, NEAPC, CRP, and neutrophil count decreased significantly after antibiotic treatment (p < 0.01).
• IL-6 and CRP levels were higher in stable CF patients compared to those at the end of an exacerbation (p = 0.007 and p = 0.01, respectively).
• IL-6 and CRP showed a strong positive correlation (r = 0.836, p < 0.0001) and were elevated in CF patients versus controls at all time points.

Conclusions:

• IL-6 and CRP are reliable markers of inflammation in cystic fibrosis, with levels decreasing after antibiotic therapy.
• Sputum IL-6 concentrations correlate with lung function and inversely with neutrophil elastase post-treatment.
• The utility of IL-6 as an inflammatory marker in CF is compartment-dependent, requiring consideration of its relationship with other markers.