Development of immunoglobulin G subclass antibodies to ovalbumin, birch and cat during the first eight years of life in atopic and non-atopic children

Immune responses to allergens in young children include both Th1- and Th2-1 ike immunity, which may regulate the secretion of immunoglobulin (Ig) G sub class antibodies differently. The time, route and level of exposure to an a llergen may be decisive with regard to whether sensitization or tolerance w ill ensue. To study this, we investigated the development of IgG subclass a ntibodies to food and inhalant allergens during childhood. The study group comprised a cohort of 96 children participating in a prospective study. IgG subclass antibodies to ovalbumin, Bet v 1 and cat dander were analyzed at birth, 6 and 18 months and 8 years by ELISA. IgG(1) and IgG(3) subclass ant ibodies to ovalbumin peaked at 18 months and then declined up to 8 years of age, whereas antibodies to the inhalant perennial allergen cat, but not th e inhalant seasonal allergen birch, increased with age. Exposure to cat and birch tended to be associated with high antibody levels to those allergens , whereas antibody levels to ovalbumin were not related to exposure to egg. The presence of positive skin prick tests and circulating IgE antibodies c orrelated with high levels of IgG subclass antibody responses to the allerg ens. Atopic symptoms were associated with high levels of IgG subclass, part icularly IgG(4), antibodies to the allergens. The difference in antibody le vels between atopic and non-atopic children was most marked at 6 months for ovalbumin. For the seasonal inhalant allergen birch, the difference was ap parent from 18 months, whereas a difference in antibody levels to the peren nial inhalant allergen cat was already present at 6 months. In conclusion, IgG subclass antibodies to food allergens peak in early infancy and are the n down-regulated, whereas antibodies to the inhalant perennial allergen cat , but not the inhalant seasonal allergen birch, increase with ap. Atopy is associated with high levels of IgG subclass, particularly IgG4, antibodies to allergens, supporting a deviation of the immune system towards Th2-like responses in atopic children.