Whether or not Heinz Küstner liked cod fish or not, he couldn’t eat it without coming out in a rash. It was the start of the 1920s and he was working as a scientific assistant in the laboratory of Karl Prausnitz at the Hygiene Institute of Wroclaw (in Poland today), and his boss saw an opportunity not to be missed.
Although Prausnitz was allergic to pollen, he could eat fish with impunity. He wondered whether it was possible to transfer Kustner’s fish allergy to himself by injecting his assistant’s filtered blood serum into his own skin at various dilutions. If Prausnitz’s hunch was right and the allergy was able to be transferred from his assistant to himself, the use of serum would at least show that the cells of the blood played no role.
The following day he injected fish extract near to the injection sites of Kustner’s serum, as well as to other areas of his skin as a kind of control measure. Prausnitz found that the areas where Kustner’s serum had been injected reacted immediately with “wheal and flare” rashes, indicating an allergic inflammation within the skin. There was no such reaction in the parts of the skin that did not receive any of Kustner’s serum.
The experiment, published in German in 1921 (and in English in 1962), became the basis of the classical method of demonstrating and quantifying allergen-specific antibodies. Prausnitz and Kustner had shown that it was possible to transfer one person’s allergy to another person via what they called “reagin” antibodies.
It was another 45 years before immunologists were able to identify reagin as an IgE class of immunoglobulin antibodies which reacts with specific antigens to induce the release of histamine and the other vasoactive amines associated with an allergic inflammation. Prausnitz has shown that it was possible to induce a skin allergy in non-allergic people and the Prausnitz-Kustner test (known as the P-K test) became a standard method of determining whether a patient was allergic to a specific antigen. It involved transferring serum from the test subject to another healthy person, essentially using the second person as a kind of living mixing vessel for antibodies and antigens.
However, because of the dangers of transmitting blood-borne infections such as HIV, the test was later replaced by the safer skin-prick test.