The γA-globulin fraction of a reaginic serum was reduced in 0.1M mercaptoethanol followed by alkylation with iodoacetate. Reaginic antibody in the preparation was inactivated by the treatment. The reduced-alkylated γA-globulin did not manifest blocking antibody activity in the Prausnitz-Küstner reaction when it was incubated with allergen. Pretreatment of allergen-coated polyaminostyrene with untreated reaginic γA-globulin decreased the activity of the immune adsorbent to combine with the reagin, whereas treatment with the reduced-alkylated sample did not, indicating that the allergen-combining activity of the reagin was greatly diminished by the reduction-alkylation treatment. The reduced-alkylated γA-globulin from either normal or reaginic serum partially blocked passive sensitization of normal human skin with reagin, suggesting that affinity of reaginic antibody for tissues remained after the treatment. The results definitely indicate that the allergen-combining site(s) in reaginic antibody in the γA-globulin fraction is degraded by the reduction-alkylation treatment.
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