Regulatory effects of antigen and antibody on the reagin response in rabbits.

The influence of antigen dosage on reagin formation to haemocyanin in rabbits was studied. Using large doses of antigen, reagin formation was more readily elicited, the induction period was shorter and the persistence of reagins in serum was longer than when low antigen doses were employed. Reagin synthesis was readily induced after intravenous administration of antigen. Immunization with antigen mixed with varying doses of IgG antibody resulted in a suppressed formation of antibodies reactive in passive haemagglutination and in a total inhibition of reagin formation. The inhibition of reagin synthesis was long-lasting and booster injections of antigen did not result in the appearance of reagins. `Hyposensitization' with series of injections of antigen or antigen–antibody mixtures resulted in an initial decrease of the reagin titres, but restoration of reagin levels was observed already about 2 weeks following cessation of the treatment. The possible implications of the results for the specific immunologic therapy of allergic disorders are discussed.