The degree of branching of the glycans of alpha(1)-acid glycoprotein in asthma - A correlation with lung function and inflammatory parameters

alpha(1)-Acid glycoprotein (AGP) is a plasma protein belonging to the group of acute-phase proteins. It contains five N-linked glycans which, dependin g on pathophysiologic state, differ in their degree of branching (i.e., in the relative proportions of di-, tri-, and tetraantennary glycans). Changes in the degree of branching of these glycans have been shown to affect vari ous immunomodulatory properties of ACP. We wanted to investigate whether ch anges occur in the branching of AGP glycans in plasma and in bronchoalveola r lavage fluid (BALF) in asthma. For this purpose, we selected three groups of patients for study: patients with atopic asthma (AA), atopic nonasthmat ic patients, and a group of patients with various interstitial lung disease s (ILDs). The plasma AGP concentration was normal in both atopic study grou ps, but was increased in ILD patients. In contrast, the branching of glycan s of AGP was altered in subjects with AA, whereas it was normal in the othe r study groups. The presence of asthma symptoms correlated with the increas ed glycan branching of ACP in both plasma and BALF. Additionally, the degre e of branching of AGP in BALF was related to FEV1, to the provocative dose of histamine causing a 20% decrease in FEV (PD20), and to the number of eos inophils. In conclusion, asthma is accompanied by changes in the branching of AGP glycans that indicate an inflammatory reaction that differs markedly from a normal acute-phase response, in which decreased branching of AGP oc curs.