The in Vivo Stability of the I131 Protein Label of Rabbit Antibody in Guinea Pigs as Determined by the Quantitative Precipitin Reaction

Open Access
Publisher Website
Google Scholar
Abstract
Summary: The fate and rate of degradation of I131 labelled rabbit antibody (antihuman albumin) was studied in the guinea pig. The labelled rabbit antibody recovered from guinea pig sera by specific precipitation was found to retain the same I131 activity per microgram of antibody nitrogen as was found in the iodinated antibody before injection into the guinea pigs. These findings indicate that the I131 label of trace-iodinated rabbit antibody did not have a metabolic fate independent of the protein molecule in the guinea pig serum. The appearance between the fifth and seventh day of circulating guinea pig antibody against the administered rabbit globulin was detected by a change in the I131/AbN ratio of the antibody recovered from the guinea pig sera at this time. The rate of disappearance of the labelled heterologous protein (rabbit antibody) from the circulation of the guinea pig was found to be an exponential function with a half-life of 107 to 113 hours. This was corroborated by the rate of disappearance of total radioactivity in the serum as well as by the rate of excretion of radioactivity. The results of the comparative precipitin reactions indicate that the I131 label and the labelled antibody are stable when heated at 56 C for 50 minutes to inactivate complement.