Serum B12 tryptase level as a marker of allergic airway inflammation in asthma

Tryptase is a specific marker of mast-cell activation and plays a part in the pathophysiology of various allergic diseases including asthma, but little is known of the spillover of this enzyme into the systemic circulation. Therefore, we measured serum levels of mast-cell-derived tryptase in 21 patients with mild to moderate asthma and 20 healthy, subjects, using a B12 monoclonal antibody-based immunofluoroassay that detects both monomers and tetramers of alpha- and beta-tryptases. There was a good correlation between serum and sputum tryptase levels, and, compared with healthy subjects (1.68 +/- 0.31 ng/ml), asthma patients had higher concentrations of serum tryptase (atopic asthma, 4.18 +/- 0.95 ng/ml, p = 0.022; nonatopic asthma, 3.93 +/- 0.82 ng/ml, p = 0.031). Although serum tryptase levels did not correlate with asthma symptom scores, peak expiratory flow, or forced expiratory volume in 1 s, they positively correlated with mast-cell and eosinophil counts (p = 0.041 and p = 0.025, respectively) and eosinophil cationic protein contents (p = 0.029) in induced sputum. These results suggest that serum tryptase detected with B12 antibody is a marker of allergic airway inflammation in asthma.