The effect of immunization on the uptake of intratracheally administered antigen

The purpose of this study in rabbits was to evaluate the effect of immunization on the uptake of intratracheally administered ¹²⁵I-labeled ovalbumin (OA) into the circulation. Immunization reduced the amount of trichloroacetic acid-precipitible antigen entering the circulation: this suppression of antigen uptake did not appear to be due to increased systemic clearance of immune complexes. The reduction of antigen appearance in the blood could largely be accounted for by factors in serum, presumably antibodies, since the reaction was immunologically specific and was transferrable to normal recipients with immune serum. The rate of antigen uptake into the blood, expressed as an appearance velocity, was reduced approximately four-fold in immunized animals compared to normal animals. In addition to reducing the uptake of OA through the lung, immunization also appeared to cause greater catabolism of the antigen in the lung.