Abstract
Background and AimSerum IgG4 concentrations are commonly measured in clinical practice. The aim of this study was to investigate serum IgG4 concentrations in adults and their potential relationship with demographic, lifestyle, metabolic, and allergy-related factors.MethodsSerum IgG4 concentrations were measured with a commercial assay in 413 individuals (median age 55 years, 45% males) who were randomly selected from a general adult population.ResultsMedian IgG4 concentration was 26.8 mg/dL. Five out of the 413 individuals (1.2%) exhibited IgG4 concentrations >135 mg/dL, and 17 out of 411 (4.1%) exhibited an IgG4/total IgG ratio >8%. Serum IgG4 concentrations were significantly higher in males than in females and decreased with age. After adjusting for age and sex, serum IgG4 concentrations were not significantly influenced by alcohol consumption, smoking or common metabolic abnormalities (obesity and the related metabolic syndrome). Serum IgG4 concentrations were not significantly correlated with serum concentrations of proinflammatory cytokines and inflammation markers. Serum IgG4 concentrations were significantly correlated with IgE concentrations. Serum IgG4 concentrations tended to be higher in atopics (individuals with IgE-mediated sensitization to aeroallergens) than in non-atopics, particularly among atopics without respiratory symptoms. Serum IgG4 concentrations were not significantly correlated with total eosinophil blood count. Cases of IgG4-related disease were neither present at baseline nor detected after a median of 11 years of follow-up.ConclusionsStudies aimed at defining reference IgG4 values should consider partitioning by age and sex. Further studies are needed to confirm the potential influence of atopy status on serum IgG4 concentrations.
Highlights
The fourth subclass of immunoglobulin G (IgG4) is the less abundant serum IgG subclass in humans [1]
Serum IgG4 concentrations were measured with a commercial assay in 413 individuals who were randomly selected from a general adult population
Serum IgG4 concentrations were not significantly correlated with serum concentrations of proinflammatory cytokines and inflammation markers
Summary
The fourth subclass of immunoglobulin G (IgG4) is the less abundant serum IgG subclass in humans [1]. The half-life of IgG4 is approximately 21 days [2] and, unlike other IgG subclasses, IgG4 does not bind complement [3] It is unique among antibodies in that IgG4 molecules can be asymmetric, i.e., a large fraction of plasma IgG4 molecules have two different antigenbinding sites, resulting in bi-specificity [4,5]. Like IgE, regulation of IgG4 production is dependent on Th2 cells [5].The function of IgG4 is not completely understood. It may play a role in allergic disorders by competing for allergen with IgE bound to mast cells, blocking their stimulation [5]. The aim of this study was to investigate serum IgG4 concentrations in adults and their potential relationship with demographic, lifestyle, metabolic, and allergy-related factors.
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