Related Experiment Video
Updated: Aug 16, 2026

Determining the Reactivity and Titre of Serum using a Haemagglutination Assay
Published on: January 29, 2010
Serum sickness
1Emeritus Professor of Medicine, Division of Dermatology, University of Ottawa, Ottawa, Ontario, Canada.
Background:
In the late 19th and early 20th century there was much interest in understanding the reactions to diphtheria antitoxin and the horse serum in which it was produced and administered.
Objective:
Pirquet and Schick reported on their studies of these reactions; particularly the differences in the reaction of those patients who had only one injection, and those who had a re-injection.
Conclusion:
Pirquet and Schick concluded that "due to a single injection of horse serum a change takes place in the reaction of the human organism to the re-introduction of the same substance." This change, Pirquet in a 1906 article, called allergy.
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