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Precipitin Test

Precipitin Test. What is it?. a serological test using a precipitin reaction to detect the presence of a specific antigen;  specifically :  a test used for determining the source of a blood stain . Precipitin tests allow human blood to be distinguished from animal blood. 

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Precipitin Test

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  1. Precipitin Test

  2. What is it? • a serological test using a precipitin reaction to detect the presence of a specific antigen; specifically: a test used for determining the source of a blood stain. • Precipitin tests allow human blood to be distinguished from animal blood.  • The test is also known as the Uhlenbuth test after the German scientist who developed it in 1901.  

  3. Procedure 1. The investigator can recover these antibodies by bleeding the animal and isolating the blood serum. This serum will contain antibodies that specifically react with human antigen (human antiserum).  2. Serum for the precipitin test is obtained from rabbits which have produced antibodies to destroy a small quantity of human blood injected into them.   3. A drop of this anti-human serum is added to suspect blood, which will precipitate its protein if it is of human origin.

  4. Commercially available • Very sensitive test • Only a tiny amount of blood is needed • Can eliminate different species blood • Cannot be used to tell you whose blood it is Strengths Weaknesses

  5. Example • Precipitin is produced by injection of the blood serum from one animal to another, which reacts, with the serum of all closely related animals. • If human serum is injected into a rabbit, the precipitin in the rabbit will precipitate the proteid, not only of humans but also of other higher apes. • Serum of a rabbit is injected with the serum of a hen it can precipitate the proteids of the hen and in the serum of a pigeon

  6. What the reaction looks like http://youtu.be/1yYYbm04YwM?t=7m24s

  7. Review Questions • How is the precipitin test performed? • Human blood is drawn and injected into a small animal, such as a rabbit. The animal’s blood serum is taken and exposed to the bloodstain in question. The reaction is observed. • What is the precipitin test looking for and what can it tell us? • It is looking for the reaction of antibodies and it tells us whether or not blood is human. • What type of evidence can this test give us? • The evidence provided from this test is class evidence. • What are the strengths of this test? • Strengths of this test include it’s ability to eliminate different species blood, it’s commercial availability, sensitivity, and only a tiny amount of blood is needed. • What are the weaknesses of this test? • Weaknesses of this test include it’s inability to tell us whose blood a bloodstain belongs to.

  8. Sources • “Recent Advances in Physiology and Bio-chemistry.” Google Books. N.p. Web. 02 Apr. 2013. • “Human or Not? Precipitin Test.” Human or Not? Precipitin Test. N.p. Web. 02 Apr. 2013.

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