The titration of scarlet fever antitoxin in rabbits / by H.J. Parish and C.C. Okell.

  • Parish, H. J. (Henry James)
Date:
1927?]
Catalogue details

Licence: In copyright

Credit: The titration of scarlet fever antitoxin in rabbits / by H.J. Parish and C.C. Okell. Source: Wellcome Collection.

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    while it took 10 c.cm. of serum “ E ” to produce the same result. With a third pair of sera the same agreement between human and rabbit tests was found. We have not yet had an opportunity of comparing sera known to be efficient in the treatment of scarlet fever with sera which proved unsatisfactory, though this is the crucial test of any method of titration. In analysing these results, it was obviously most important to decide whether the protection of the rabbits was due to antitoxin per se, or to some other protective antibody produced in the horse in response to immunisation. The following observations have a bearing on this question : (1) Many of the sera were experimentally made by injecting horses with bacteria-free filtrates of young cultures of streptococci, and were therefore as purely antitoxic as could be prepared. (2) The serum of rabbits highly immunised against washed (toxin free) streptococci, though rich in agglutinins, had no protective value. (3) Human convalescent serum had a small but definite protective value. (4) The protective power of antitoxic sera against culture was lost if the serum had previously been treated with an adequate amount of toxin. (5) Scarlet fever toxin, when given intravenously in sufficiently large quantities, killed 80 to 100 per cent, of rabbits. Scarlet fever antitoxin protected rabbits from death due to toxin, while normal horse serum and concen¬ trated diphtheria antitoxin were without protective value. These observations possibly provide a means of titrating scarlet fever toxin and antitoxin without the use of culture. These results, further details of which will be published at a later date, in conjunction with the agreement obtained with human tests, suggest, if they do not prove, that the test is a measure of “ antitoxin ” per se. It may be added that though scarlet fever anti¬ toxin protects rabbits against haemolytic streptococci from cases of scarlet fever, it also protects against the septicaemia due to certain other haemolytic strains which have no obvious connexion with scarlet fever. It is not clear at this stage, therefore, to what extent the test can be used conversely to identify the scarlet fever streptococcus. Before this question can be answered it would be necessary to have much more information about the immunological relationships between streptococci of the haemolytic group and their toxins than is yet forthcoming.