Toxin - antitoxin reaction is the interaction of a toxin with antibodies (antitoxins) contained in a specific antiserum. Toxins (see) and antitoxins (see) are able to connect in various proportions; the resulting complex can dissociate. Under certain conditions, the reaction results in neutralization of the toxin. With an excess of toxin, its mixture with antitoxin may be poisonous.
Toxin - antitoxin reaction is strictly specific. This makes it possible to use it for diagnostic purposes in identifying toxins of pathogens of various infectious diseases (botulism, diphtheria, etc.). For these purposes, the material under study is administered to an animal (experiment); another animal is given the same material after being treated with an antitoxin (control). The effect of the toxin should be manifested only in the first of the experimental animals. Toxin - antitoxin reaction in vitro can be observed in the form of precipitation (see).