The Relation of Serum Fractions to Serum Sickness in Rabbits. ∗

Abstract

We have previously shown that injection of rabbits with from 5 to 10 cc. of horse serum per kilo of body weight, will cause the appearance of serum sickness in a large percentage of the animals. The reactions which we have considered as those of serum sickness are noted upon the rabbits' ears 4 to 8 days after injection. 1

An attempt was made to determine whether or not the fractions euglobulin, pseudoglobulin and albumin of horse serum, might be or might contain the agent related to the causation of serum disease. Accordingly, these serum fractions 2 were injected into white rabbits in various dosages and with the results listed in Table I. The horse serum fractions used were from both normal and diphtheria toxin immune animals. In the present and in previous comparative studies, we have noted little or no difference between normal and immune sera, or between their respective fractions, in ability to cause serum sickness.

It is to be noted that a dose (per kilo of body weight) of 150 mg. of euglobulin nitrogen brought about serum sickness in 7% of 30 animals, while smaller doses of euglobulin were without effect in causing serum sickness. Pseudoglobulin was more active, with reference to the amounts injected, since a dosage of 150 mg. nitrogen per kilo brought about serum sickness in 80% of 25 animals. Smaller doses (i. e., from 71 to 100 mg. nitrogen) of this fraction resulted in a decreased occurrence of serum sickness and since none of the animals receiving 35 mg. of nitrogen per kilo developed the disease, it may be inferred that under these conditions the threshold for development of serum sickness in the most susceptible animals lies at a dosage of between 35 and 71 mg. pseudoglobulin nitrogen per kilo.