Background: Exposure to allergen may induce a modified T(H)2 response characterized by high IgG(4) levels, absence of IgE sensitization, and a decreased risk of allergic respiratory symptoms.
Objective: To assess the association of IgG(4) level with allergic respiratory symptoms in a community-based sample of adults.
Methods: Information on exposure to cats, respiratory symptoms, and mattress allergen levels was obtained from 2780 adults. Levels of cat and house dust mite (HDM) specific IgE, IgG, and IgG(4) were measured. The association of exposure to allergen with IgG(4) and of IgG(4) with symptoms was assessed.
Results: Geometric mean (GM) cat specific IgG and IgG(4) was higher in subjects who had a cat that was allowed in the bedroom than in subjects without a cat (adjusted ratio of GM IgG(4), 1.41; 95% CI, 1.25-1.57). Levels of HDM specific IgG and IgG(4) were similar in subjects with undetectable and high (>20.22 microg/g) mattress Der 1 levels (adjusted ratio of GM IgG(4), 1.02; 95% CI, 0.89-1.17). There was no evidence that high cat or HDM specific IgG(4) levels were associated with less IgE sensitization or with fewer symptoms.
Conclusion: In this community-based sample of adults, high IgG(4) levels to cat or HDM were not associated with a lower risk of allergic respiratory symptoms.
Clinical implications: In adults, high cat allergen exposure does not protect against respiratory symptoms.