Abstract
The element of fixation that accompanies sensitization was well demonstrated by Opie, 1 who cut out the inflammatory area resulting from subcutaneous injection of the specific protein in a sensitized rabbit, extracted the ground tissue with salt solution, and established the presence of the antigenic substance in the fluid by testing it with the serum of a specifically sensitized rabbit. In this laboratory, the aspect of fixation was studied from another point of view. The question was raised, whether an animal sensitized to horse serum would fix diphtheria antitoxin at the point of injection. Accordingly, the following conditions were experimentally established: (1) 50 MLD of diphtheria toxin injected intracutaneously in rabbits of about 3 kg. weight, cause death in from 2 to 4 days. (2) The same dose of toxin and 50 units antitoxin injected intracutaneously 1 inch apart, result in the survival of the animals.
A group of rabbits previously sensitized to horse serum was given the toxin and antitoxin injections intracutaneously, employing non-sensitized rabbits as controls. It was found that the control animals survived this treatment while the sensitized animals, showing a marked inflammatory response at the area wherein the antitoxin was injected, succumbed within 2 to 4 days, unquestionably because the fixation of the antitoxin at the point of injection prevented its neutralizing action on the toxin. Table I gives the results obtained with 11 rabbits.
Three rabbits sensitized intracutaneously with horse serum and 3 others sensitized intravenously, succumbed to the toxin and antitoxin injections. Three normal rabbits and 2 others sensitized to human serum survived the same treatment. Four of the rabbits sensitized with horse serum received but one injection of this reagent. One additional rabbit (79) sensitized to horse serum and one non-sensitized control (79 1 ) received 50 units of antitoxin intracutaneously 48 hours before the injections of 50 units of antitoxin and 50 MLD of toxin.
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