Exhaled breath markers of alveolar macrophage activity in sarcoidosis

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.

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.

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.

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.