Exhaled breath markers of alveolar macrophage activity in sarcoidosis.

Objective: Granuloma formation in sarcoidosis is dependent upon the interaction between alveolar macrophages (AMs) and a CD4+-driven TH1 response. This study aimed to measure TNF-α and calcium ion concentrations as markers of AM activity, in addition to total protein as a non-specific inflammatory marker in the exhaled breath condensate (EBC) of patients with sarcoidosis as well as control subjects.

Methods: EBC was collected from 17 sarcoidosis patients and 23 healthy volunteers. Protein was measured by the bicinchoninic acid assay, TNF-α concentration was measured by ELISA and Ca(2+) concentration was measured by inductively coupled plasma-mass spectrometry. Conductivity of EBC was assessed using a conductivity probe.

Results: Total protein concentration was significantly elevated in EBC from patients with sarcoidosis compared to control subjects (19.51 ± 4.52 vs. 10.60 ± 1.31 µg/ml, p = 0.020), as was TNF-α (3.37 ± 0.38 vs. 2.59 ± 0.40 pg/ml, p = 0.037) and conductivity (66.68 ± 16.73 vs. 36.85 ± 3.070 µS/cm, p = 0.044). EBC Ca(2+) concentration was significantly higher in healthy controls compared to patients with sarcoidosis (116.50 ± 12.19 vs. 73.88 ± 13.35 µmol/l, p = 0.018), although this was in the context of normal serum Ca(2+) in the sarcoidosis cohort.

Conclusions: Total protein and TNF-α concentrations were elevated in EBC from patients with sarcoidosis and could indicate disease activity. The reduction in EBC Ca(2+) concentrations could represent granulomatous activity in the lung.