Precipitin

Serum precipitin test ( synonymous Uhlenhuth sample ) is a serological relationship detection, the is based on the precipitation of sera with antigens in the blood serum, having a relationship related to the similarity of the antigen used for the preparation of the immune serum.

The test is based on the specific antigen -antibody reaction for detecting the coincidence of two antigenic organisms in terms of their proteins ( interchangeably proteins). Each species has species-specific proteins and therefore can be determined with this test, the degree of similarity. The antibodies present in the serum through contact with antigen, depending on the affinity for the antigen that was used to generate the serum, a precipitation (synonym precipitation, precipitation ) the solute in the blood serum proteins. The more similar are the amino acid sequences of the serum proteins used, the greater the genetic match, resulting in a greater affinity and greater precipitation by the serum follows. This line of reasoning also applies vice versa. The test was applied in addition to the determination of the species of an unknown blood sample for quantitative analysis of phylogenetic relationships ( phylogeny ) and also for the detection of admixtures of non- declared species in meat and sausage.

Method

The precipitin test can be used widely for the study of kinship relations, in the following it is described for the investigation of a relationship to human blood. According to him but could also perform for other organisms. First, the so-called human serum is needed that you win by letting stand for some time in a test tube human blood, so that the solids settle at the bottom of the test tube and above the remaining liquid ( plasma without fibrinogen). This serum is injected a rabbit or another intermediate organism, which in turn removed after a few weeks the blood.

With the rabbit blood is carried by the above method for the separation of the serum from the liquid, thus gaining a new serum containing anti -human serum, which contains antibodies to human serum proteins. If you mix this anti-human serum now with human blood, so there is a ( precipitation ), since these antigens are immediately attacked by antibodies. The maximum possible (at 100 % identity) precipitation of the antigen-antibody complex is defined as a 100 per cent precipitation (as reference standard ). A related negative control carried along, as far as possible sample does not lead to a lack of affinity precipitation.

For other living beings there with this anti -human serum results vary, with this, the degree of precipitation allows conclusions on the phylogenetic proximity. The more proteins are precipitated by the antibodies contained in the anti-human serum, the more similar the organisms are human beings in terms of proteins. Because specific proteins of any organism have evolved in the course of evolution, suggests a great similarity in attention to the proteins on a large phylogenetic proximity between two organisms. However, since the precipitin reaction provides a poorly differentiated result, can not be used in all groups of animals and no precise conclusions as to permit, when the lines of development of two living beings have separated, she has now lost much of its importance. Instead, a genetic fingerprint is now examined more with the DNA sequencing, the amino acid sequence analysis ( by Edman degradation ), the restriction fragment or to DNA -DNA hybridization.

Example

Below is performed by human serum proteins in relation to humans, chimpanzees, gorillas, orangutans, baboons, cattle, sheep, deer, horses, marsupials, birds and rabbits as an example of the serological relationship investigation. The intermediate body for extracting the test serum (in this case an anti -human serum) is a rabbit.

Procedure

  • It is taken from the people and injected into a rabbit blood serum.
  • After some time, the rabbit antibodies against the proteins of humans (: against antigenic proteins and carbohydrates accurate) forms.
  • Now, blood is withdrawn from the rabbits and prepared from the test serum.
  • The test serum is added to blood samples from human, chimpanzee and orangutan.
  • There is a clumping ( precipitation / precipitation ) of the blood in the test serum, depending on how strong fit the antibodies to the antigens.

Result

  • Man: 100%
  • Chimpanzee: 83 %
  • Gorilla: 64 %
  • Orangutan: 42%
  • Baboon: 29%
  • Beef: 10%
  • Sheep: 18%
  • Hirsch: 7%
  • Horse: 3%
  • Marsupial: 0%
  • Vogel: 0%
Paul Uhlenhuth Serum (blood) Blood plasma
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