Allergenicity of major cow's milk and peanut proteins determined by IgE and IgG immunoblotting (original) (raw)

Background: Speci®c IgG antibodies are frequently observed in food-allergic patients. However, the allergen-fraction speci®city of IgG antibodies in relation to IgE antibodies is not well de®ned. Our aim was to determine the IgE and IgG antibody pro®le to major cow's milk and peanut-antigen fractions in foodallergic patients and tolerant individuals. Methods: Sera were collected from 10 patients allergic to cow's milk and 10 patients allergic to peanuts, as well as from 20 control subjects. Cow's milk and peanut proteins were migrated on SDS±PAGE and immunoblotted for IgE, IgG, and IgG4 antibodies. Food-speci®c IgE concentrations were measured by CAP System FEIA 2 , and IgG and IgG4 concentrations by ELISA. Results: In food-allergic children, similar fraction-speci®c IgE, IgG, and IgG4 antibody-binding pro®les to the major cow's milk or peanut antigens were found. In nonallergics, the presence of fraction-speci®c IgG antibodies was mostly dependent on regular ingestion of the food. The presence of speci®c antibody on immunoblots correlated with their quantitative measurement. The mean value for speci®c IgE in cow's milk-allergic patients was 450t1326 IU/ml, and 337t423 IU/ml in peanut-allergic patients. Speci®c IgG antibody values in milkallergic patients were not different (median OD 1.5, range 0.3±2.3) from controls (median OD 1, range 0.2±1.8). However, in peanut-allergic patients, IgG concentrations were signi®cantly higher than in controls (OD 1.2 [0.5±1.3] vs 0.5 [0.3±0.7]; P<0.01). Conclusions: Similar fraction-speci®c IgE and IgG antibody pro®les in allergic individuals suggest a common switching trigger involving both isotypes. Intrinsic allergenicity might explain identical IgG antibody fraction speci®city in nonallergics and in allergics. The presence of IgG antibodies in nonallergics was related to regular ingestion of the food.