A sensitive biological test has been used to detect the persistence of minute traces of a foreign protein, bovine γ-globulin, in the blood and livers of rabbits intravenously injected with it, as an antigen. At various intervals after injecting these rabbits (donors) serum or liver tissue was transferred from them to the peritoneal cavities of normal or unilaterally adrenalectomized mice (recipients) with the aim of rendering the latter hypersensitive to the antigen that might be persisting in the transferred materials; a state of affairs detectable, 2 days later, by the appearance of signs of reversed passive anaphylaxis when the recipient mice were intravenously challenged with a strong anti-bovine γ-globulin rabbit serum.
The protein persisted in the blood of the donor rabbits, in readily demonstrable amounts for 1 month, and in the blood of one animal, in minute traces, or as long as 6 weeks. It was detectable in the livers for 8 weeks.
The persistence of bovine γ-globulin in rabbits, which form circulating antibodies to it well, is not as long as that in mice, which form antibodies to it poorly, since in previous work with the mouse the antigen was found (1) in the blood after 8 weeks and in the liver for 14 weeks. Nevertheless the antigen persists in the rabbit much longer than is generally supposed. Indeed it can be found in the liver all through the period in which circulating antibody is demonstrable in the blood. Explanations for the phenomenon have been suggested. Its significance in relation to the mechanisms of antibody formation is obvious.