Allergen-induced Th1 and Th2 cytokine secretion in relation to specific allergen sensitization and atopic symptoms in children

Background Allergic diseases are believed to be due to T helper (Th)2-like immunity to allergens in affected tissues, and immune responses to allergen s are characterized by a cross-regulation between Th1 and Th2 cells. Atopic individuals may develop IgE antibodies to only one or more allergens. Howe ver, the mechanisms behind sensitization to a specific allergen, e.g. why a n individual develops IgE to cat but not birch, are not known. Our aim was to study birch- and cat-induced Th1 and Th2 cytokine secretion in children who were sensitized to: birch but not to cat, and vice versa. Materials and methods The subjects in the study were 60 12-year-old childre n. Seventeen of the children were sensitized (skin prick test and circulati ng IgE positive) to birch but not cat, 13 were sensitized to cat but not bi rch, 11 were sensitized both to birch and cat, and 19 children were skin pr ick test and circulating IgE negative. Forty-six children had a history of atopic symptoms, and 42 of them had current symptoms. Peripheral blood mono nuclear cells were separated from venous blood and stimulated with cat or b irch allergen. The levels of IL-4, IL-5, IL-9, IL-10, IL-13 and IFN-gamma i n the cell supernatants were analysed by ELISA. Results Sensitized children produced more of the Th2 cytokines IL-4, IL-5, IL-9 and IL-13 than non-sensitized atopic and non-atopic children in respon se to stimulation with the allergen they were sensitized to. High levels of the Th2 cytokines IL-4 and IL-5 and low levels of the anti-inflammatory cy tokine IL-10 were associated with atopic symptoms, and high cat induced IL- 9 levels with asthma, Conclusions The Th2 cytokines IL-4, IL-5, IL-9 and IL-13 were all commonly detected in sensitized children after stimulation with the specific, in con trast to an unrelated, allergen. Atopic symptoms were associated with incre ased level's of IL-4 and IL-5 and tended to be associated with low levels o f IL-10, and asthma with high cat-induced IL-9 levels.