The use of radioactive isotopes in immunological investigations. 10. The fate of some intravenously injected native proteins in normal and immune rabbits

Abstract

Horse-serum gamma-globulins and bovine-plasma albumin, both trace-labeled with I13l, were injected intravenously into normal rabbits, and their persistence in the blood stream measured during the first 2 hours after injection. A relatively small loss of the protein is observed during this period; it was shown that this loss is frequently brought about by 2 processes (the "fast reaction" and the "slow reaction"). A method for calculating the amounts of protein acted upon by each of these processes is described. When the same proteins were injected into specifically immunized rabbits, a much larger proportion of the protein was removed from the blood by the fast reaction, probably owing to an in vivo precipitin reaction followed by a rapid phagocytosis of the precipitate. The rapid removal of bovine-plasma albumin from the blood of immunized animals was occasionally observed in rabbits which had received a single immunizing injection of the antigen 14 days previously, but this phenomenon was not observed 2, 5, and 9 days after the immunizing injection. Soluble antibody-antigen complexes containing trace-labeled bovine-plasma albumin are removed from the blood of normal rabbits only slightly more rapidly than the antigen itself. After the injection of antigens into immune rabbits, considerable deposition of antigen occurs in the liver, lungs and spleen. If such small amounts are injected that 80-90% of the injected antigen is removed from the blood in 1 hour, the recovery of I131 in these organs is almost equal to that which has disappeared from the blood.