Mixtures of ragweed pollen extract with a fraction of an allergic serum containing reagin gave erythema-wheal reactions in normal individuals. Skin reactivity was not induced either with the fraction which had been heated at 56° C. for 4 hours or with the γ2-globulin fraction of the same serum. The skin reactions with the allergen-reagin mixtures were inhibited by prior treatment of the skin sites with normal γ1A-globulin, but not with γ2- or γ1M-globulin. After removal of free allergen in the mixture by gel filtration, no reaginic activity was recovered. A skin-reactive substance was eluted from a Sephadex G-200 column in the fractions containing γ1A-globulin. The results definitely indicate that allergen-reagin complexes formed in vitro have an activity to induce erythema-wheal reactions in normal individuals.
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