Antitoxins

special substances (antibodies) formed in the organism of animals or man upon entry into it of toxins—that is, poisons of bacterial or animal origin. Every antitoxin has a strictly specific effect; it renders harmless (neutralizes) only that toxin under the influence of which it was formed (for example, only the toxin secreted by the causative agent of diphtheria is neutralized by diphtheria antitoxin), and it has no neutralizing effect on other toxins. Antitoxins are gamma globulins that are capable of interacting specifically with toxins.

Antitoxins are used in medical practice in the form of antitoxic sera (antidiphtheria, antitetanus, antidysentery, antigangrene, antibotulinum, antiscarlatina, antivenom, and so on), which are obtained by subcutaneous injection of a horse (or other animal) with toxins or anatoxins; antitoxin is thereupon formed in the blood serum of the horse. Blood serum containing antitoxin is widely used in prophylaxis and treatment of diphtheria, tetanus, botulism, and other diseases, and it is also used for treatment of persons bitten by poisonous snakes. The therapeutic and prophylactic properties of immune sera are determined by their strength, which is measured in conventional antitoxic units (AU). Thus, 1 AU of diphtheria antitoxic serum is considered to be that quantity of the serum which neutralizes 100 minimum lethal doses of diphtheria toxin when injected into a guinea pig weighing 200–250 g.

Methods of purifying and concentrating antitoxic sera have been elaborated which permit production of preparations that have high AU content and are free of inert substances.