BACKGROUND

In 1993 extremely high levels of birch-pollen were recorded in Stockholm, Sweden. This provided an opportunity to evaluate the effects of aeroallergen exposure (exp.) on the early immune response.

OBJECTIVE

To assess the influence of exp. to birch-pollen during pregnancy and infancy on the allergen-specific IgE- and IgG4-antibody (ab) response and the development of atopic disease in children.

METHODS

A total of 970 children with atopic heredity and born in Stockholm 1992, 1993 or 1994 were investigated at age 4.5-5 years. They were divided into five groups; high-dose exp. at 1 year of age, high-dose exp. at 0-3 months, low-dose exp. at 0-3 months, high-dose exp. during pregnancy and low-dose exp. during pregnancy. The children were examined and skin prick tested with inhalant and food allergens. IgE abs (against birch-pollen and recombinant Bet v 1(rBet v1)) and IgG4 abs (against rBet v 1) were analysed in serum. All children were assembled in one group to assess the effects of different ab responses (IgE/IgG4) on the development of atopic disease.

RESULTS

Children exposed to high doses of birch-pollen during the first 3 months of life more often had detectable levels of IgG4 abs to rBet v 1 than the children in the other groups (P < 0.001), independent of sensitization to birch. Overall, the risk of allergic rhinoconjunctivitis was increased among children sensitized to birch-pollen and appeared more pronounced in children without detectable levels of IgG4 ab to rBet v 1 (Odds ratio 9.4; 95% Confidence interval: 5.5-16.1). IgE sensitization to birch-pollen seemed to have a stronger influence on the development of atopic disease than the IgG4-ab response.

CONCLUSION

Exposure to high doses of inhalant allergens during the early postnatal period is associated with detectable levels of allergen-specific IgG4 ab even at 5 years of age. An immune modulating effect by IgG4 on symptoms of allergic rhinoconjunctivitis is suggested in children sensitized to birch.