Cat and dust mite allergen levels, specific IgG and IgG4, and respiratory symptoms in adults

BackgroundExposure to allergen may induce a modified TH2 response characterized by high IgG4 levels, absence of IgE sensitization, and a decreased risk of allergic respiratory symptoms.ObjectiveTo assess the association of IgG4 level with allergic respiratory symptoms in a community-based sample of adults.MethodsInformation 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 IgG4 were measured. The association of exposure to allergen with IgG4 and of IgG4 with symptoms was assessed.ResultsGeometric mean (GM) cat specific IgG and IgG4 was higher in subjects who had a cat that was allowed in the bedroom than in subjects without a cat (adjusted ratio of GM IgG4, 1.41; 95% CI, 1.25-1.57). Levels of HDM specific IgG and IgG4 were similar in subjects with undetectable and high (>20.22 μg/g) mattress Der 1 levels (adjusted ratio of GM IgG4, 1.02; 95% CI, 0.89-1.17). There was no evidence that high cat or HDM specific IgG4 levels were associated with less IgE sensitization or with fewer symptoms.ConclusionIn this community-based sample of adults, high IgG4 levels to cat or HDM were not associated with a lower risk of allergic respiratory symptoms.Clinical implicationsIn adults, high cat allergen exposure does not protect against respiratory symptoms.