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TOXIN — ANTITOXIN REACTION — a special case of reaction antigen — an antibody, in a cut as antigen toxins of gram-positive bacteria or poisons of nek-ry plants and animals, and act as antibodies — the anti-toxic antibodies which are formed as a result of immunization by toxins or anatoxins. Feature of T. — and. the river is that at certain ratios toxin (see) and antitoxin (see) the complex deprived of toxicity is formed.

T. — a.r. is the cornerstone seroimmunities (see), serotherapy (see) and serodiagnosis (see. Serological researches) toksinemichesky infections. Ability of anti-toxic antibodies to neutralize toxin formed the basis of practical use of anti-toxic serums for prevention and treatment of toksinemichesky infections, such as diphtheria (see), tetanus (cm), gas gangrene (see. Mephitic gangrene), botulism (see), in a pathogeny to-rykh a leading role is played by the toxins formed by the activator. Active immunization against listed inf. diseases carry out by anatoxins (see), antibodies to the Crimea actively neutralize toxins. The method which is also widely used in medical practice biol is based on a phenomenon of neutralization of toxin at its reaction with anti-toxic antibodies. titration of anti-toxic serums according to toxicity of the mixes containing a titrable antiserum in the increasing quantities and constant amount of previously standardized toxin (see. Antitoxins ).

As visible manifestation of reaction of in vitro serves formation of a flokku-lyat — an insoluble complex toxin — antitoxin in conditions fiziol. salt content and neutral reaction of the environment. Opening by G. Ramone in 1923 of a phenomenon of flocculation allowed to investigate T. — and. river by means of quantitative immunochemical methods. On the basis of this phenomenon G. Ramone in 1923, Dean and Webb (H. R. Dean, R. Webb) in 1926 offered a method of assessment in vitro of specific activity of anti-toxic serums. At a comparative research T. — a.r. by method biol. titration and reactions flocculations (see) it was revealed that optimum proportions of toxin and antitoxin in a flocculation test and a neutralization test of toxin generally match. However sizes of the relation of activities of antiserums, certain in vivo and in vitro, according to Glenni (A. T. of Glenny, 1924), can change. The flocculation test reflects not toxic, but antigenic properties of toxin and therefore titration according to Ramón though it more simply, did not replace at standardization of antitoxins of a method of titration of in vivo.

Neutralization of toxin antitoxin is defined not only their ratio in reaction, but also way of their mixing. This phenomenon (see. Danisha phenomenon ), described in 1902 by J. Danysz, is that if a certain amount of toxin, a cut is neutralized at single-step addition to a certain dose of antitoxin to add to the same dose of antitoxin in the fractional portions through certain time slices, then the formed mix is toxic. However toxicity of mix disappears after its incubation within several days that it is possible to charge to dissociation of originally formed complex and a reassotsiation of toxin and antitoxin in other proportions. If at statement of T. — a.r. to use monovalent fragments of anti-toxic antibodies, distinctions in protective action of these fragments are not observed both at single-step, and at fractional addition of toxin.

T. — and. the river is reversible: at dissociation of complexes toxin — antitoxin toxins and antitoxins, full-fledged on the physical and chemical and biological properties, are formed.

Bibliography: Boyd U. K. Fundamentals of immunology, the lane with English, M., 1969; To at l ý-@ e r A. Ya., Volgin Yu. B. and B and r t about in and L. M. Comparative study of anti-toxic properties of serums of birds, immunizirovanny tetanin and * anatoxin, Shurn. mikr.; Sheed. and immun., No. 1, page 78, 1972, bibliogr.; To e about t E. A. and Meyer M. M. Experimental immunochemistry, the lane with English, M., 1968; Carpenter Ph. L. Immunology and serology, Philadelphia, 1975.

A. Ya. Kulberg, I. A. Tarkhanova.