Microbiological neutralization reactions of antibodies in microbiological diagnosis

2021-08-22 09:38 PM

The toxins mentioned here are exotoxins. If a lethal dose or greater of the toxin is mixed with an adaptive amount of the reciprocal antitoxin and then injected into a susceptible animal, the animal is not in danger

Principles

Specific antibodies can neutralize toxins, the virulence of microorganisms, lose some properties of microorganisms or its products.

Toxin neutralization reaction

Toxins here are exotoxins. If a lethal dose or greater of the toxin is mixed with an adaptive amount of the reciprocal antitoxin and then injected into a susceptible animal, the animal is not in danger. The toxicity of the toxin has been neutralized by antitoxin. As with other immune responses, this response is very specific: a toxin only neutralizes the corresponding antitoxin.

The amount of antitoxin required to neutralize an amount of toxin depends on how the two structures are mixed because depending on experimental conditions the toxin is able to combine with antitoxin in different proportions. If, instead of adding a known amount of toxin to an antitoxin for neutralization, double the amount of the toxin is added to the antitoxin, the mixture is not neutral to laboratory animals. That is the Danysz phenomenon. It is thought that when half of the toxin is added to the antitoxin, the toxin combines with more of the antitoxin, and therefore the small number of free antitoxin molecules remaining is not sufficient to neutralize the remaining toxin. .

Virus neutralization response

Many viruses grown in cell culture destroy cells (pathological cellular phenomenon), but if the corresponding antibody of the virus is added to the virus at the same time, the virus is neutralized and cannot multiply and the Pathological cells do not occur. This reaction is used to determine the serum antibody level as well as to determine the virus type.

On the other hand, it is also possible to quantify virus antibodies in serum by mixing antisera with the virus and then injecting the mixture into a group of susceptible animals. If the test animal shows no symptoms, the presence of neutralizing antibodies has been demonstrated.

Enzyme neutralization reaction

Many bacterial enzymes have good antibiotic properties and stimulate the formation of antibodies such as streptolysin O, streptokinase of streptococcus promotes the formation of anti-streptolysin O (anti-streptolysin O - ASO), anti-streptokinase (anti streptokinase - ASK). . Based on the principle of a quantifiable neutralization reaction against streptolysin O (ASO), anti-streptokinase (ASK) in the patient's serum to diagnose streptococcal infection. In particular, the ASO test to detect anti-streptolysin O antibodies is used in the diagnosis of rheumatic heart disease and acute glomerulonephritis following group A streptococcal infection.