Toxicity of Equine Serum Treated by Alkali

Abstract

Observations on the removal of antigenicity of proteins by alkali were early made by Wells, 1 TenBroeck 2 and have been confirmed and extended by a number of later workers. Recently, Davis and Eaton, 3 as well as Kazal, DeFalco and Arrow, 4 paid special attention to the toxicity of the resulting products but came to apparently conflicting conclusions. The former found alkali-treated bovine serum albumin to be non-toxic for white mice, rabbits, and for 2 dogs when given intravenously. On the other hand, Kazal et al. confirmed an earlier report by Lewis 5 that purified bovine plasma protein treated by sodium hydroxide gained acute toxicity for guinea pigs as soon as its antigenicity was lost. In view of the importance of these findings especially in relation to possible practical application, it seems worthwhile to make a similar study on horse serum treated by alkali and to observe its toxicity in rabbits, guinea pigs, and white mice. The results obtained are herewith presented.

After several preliminary trials, it was found that one-quarter normal solution of sodium hydroxide would, after a period of 30 days at 37°C, render normal horse serum so altered in antigenicity that rabbits immunized with the treated serum produced no precipitin against both normal and treated sera, gave occasional complement fixation reaction with either, and in half of these immunized animals, skin allergy to normal serum alone was demonstrated. Furthermore, of 10 guinea pigs sensitized to treated serum, only 3 out of 7 reacted mildly with normal, and 4 out of 6 similarly to alkali-treated serum without a single death. At the same time, 4 controls died when shocked with normal serum. Nine rabbits tolerated as much as one gram of treated serum protein per kilo body weight without any symptoms, whereas only 5 out of 12 immunized rabbits reacted with an elevation of body temperature to half a degree Centigrade following intravenous injections of 20 ml (800 mg protein) of the treated serum.