The role of circulating food antigen-specific lymphocytes in food allergic children with atopic dermatitis

In this study we evaluated antigen-specific in vitro responses of peripheral blood lymphocytes to lipopolysaccharide (LPS)-depleted food allergens in children who reacted to food challenge (cow's milli or hen's egg) with a deterioration of their atopic dermatitis (AD). Some of the children showed immediate symptoms (urticaria, bronchial asthma or gastrointestinal symptoms) as well. The proliferation of casein-stimulated lymphocytes from children reacting to cow's milk (age 0.7-5.9 years) was significantly higher (P<0.01) than the proliferation of lymphocytes from 15 children with AD without milk allergy (age: 2.1-9.1 years). Twenty-eight T-cell clones (TCC) were established from the blood of three children sensitized to cow's milli and hen's egg who reacted to double-blind placebo-controlled oral food challenge both with a deterioration of AD and with immediate symptoms. Surprisingly, 16 of 28 casein- or ovalbumin-specific TCC were CD8+. All TCC produced high amounts of IFN-gamma upon stimulation with concanavalin A. In addition, 75% of the CD4+ TCC and 44% of the CD8+ TCC secreted IL-4. Our results indicate that: (i) food-specific proliferation of blood lymphocytes can be detected in patients with clinically relevant food allergy with LPS-depleted allergens in vitro and (ii) circulating food-specific lymphocytes are CD4+ and CD8+ T cells with the capacity of producing both type 1 and type 2 cytokines.