On a new factor in passive anaphylaxis

After active sensitization guinea-pigs remain hyper-sensitive for at least three years—probably for life. After passive sensitization with homologous serum, i. e., with the blood of an immune guinea-pig, they retain the sensitive condition so conferred for a period of 60 or 70 days at least. After passive sensitization with heterologous serum, i. e., with the blood of immune rabbits, they lose the sensitive condition in 10 days or less. This rapid loss has never been explained. It might theoretically be due to the development by the injected guinea-pig of immune substances directed against the introduced rabbit serum, which would then neutralize or destroy the rabbit anti-bodies, on the presence of which sensitization depends. This theory would explain the fact that the injected guinea-pigs retain their sensitiveness for about ten days, which would correspond to the time necessary to develop antibodies.

In order to test this idea, normal guinea-pigs were given a subcutaneous injection of normal rabbit serum. After eight days they were sensitized with a very large dose of the serum of a rabbit immunized against horse serum, given intra-peritoneally. Two days later, when tested by an intravenous injection of horse serum, they failed to manifest any symptom of anaphylaxis. The controls, although sensitized with a much smaller dose of immune rabbit serum, and intoxicated with about one fiftieth of the amount of horse serum used in the previous series, succumbed without exception.

The refractory state towards passive sensitization, as thus induced, may occasionally be demonstrated within three days of the first injection.

Partial immunization of guinea-pigs against rabbit antibodies can sometimes be obtained by the previous injection of sheep serum. It is, therefore, not strictly specific.