Am. J. Respir. Crit. Care Med.,
Volume 161, Number 6, June 2000, 1972-1978
The Degree of Branching of the Glycans of
1-Acid
Glycoprotein in Asthma
A Correlation with Lung Function and Inflammatory Parameters
MICHEL M.
VAN DEN HEUVEL,
DENNIS C. W.
POLAND,
CASPER S.
DE GRAAFF,
ELISABETH C. M.
HOEFSMIT,
PIETER E.
POSTMUS,
ROB H. J.
BEELEN,
and
WILLEM
VAN DIJK
Departments of Cell Biology and Immunology, and Medical Chemistry, Faculty of Medicine, and Department of Pulmonary Medicine,
Academic Hospital, Vrije Universiteit, Amsterdam; and Department of Pulmonary Medicine, Medisch Centrum Alkmaar, Alkmaar,
The Netherlands
1-Acid glycoprotein (AGP) is a plasma protein belonging to the
group of acute-phase proteins. It contains five N-linked glycans which, depending 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 various immunomodulatory properties of AGP. We wanted to investigate whether
changes occur in the branching of AGP glycans in plasma and in
bronchoalveolar lavage fluid (BALF) in asthma. For this purpose,
we selected three groups of patients for study: patients with
atopic asthma (AA), atopic nonasthmatic patients, and a group of
patients with various interstitial lung diseases (ILDs). The plasma
AGP concentration was normal in both atopic study groups, but
was increased in ILD patients. In contrast, the branching of glycans of AGP was altered in subjects with AA, whereas it was normal in the other study groups. The presence of asthma symptoms
correlated with the increased glycan branching of AGP in both
plasma and BALF. Additionally, the degree 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 eosinophils. 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 occurs.