When the term blood test is used, it typically refers to blood typing. Blood testing can also be used in parentage, DNA analysis and when in search of genetic markers. One of the less common uses is to determine human blood from non-human, like the Uhlenhuth Test. In the field of pathology, this test is known as the precipitin test and has a short history of making great strides in the field of forensics.
The Uhlenhuth Test serves as a forensic and non-forensic test used to detect the existence of antibodies. It can also used to determine the paternity of children and blood typing. Blood type tests also help to qualify or disqualify criminal suspects.
The evolution of the Uhlenhuth Test began with the Precipitin Test. Rudolf Kraus was responsible for discovering that bacterial filtrates, when injected into rabbits created a precipitin. Furthermore, when the precipitin was incubated with the bacterial filtrates, it created a precipitation reaction.
In the year of 1901, a German scientist by the name of Paul Uhlenhuth was asked to use the test that he had developed in a double murder investigation. Ludwig Tessnow was accused of brutally murdering two boys and leaving their unrecognizable bodies in the forests of Rugen, Germany.
Just prior to this crime, Uhlenhuth had experimented at the university of Greifswald with injecting into a rabbit, chicken egg proteins. He then extracted blood from the rabbit, mixed it with egg whites to help the observation and it resulted in clumping. This clumping was called a precipitin. This test was used on the blood stains found on Tessnow’s clothes and he was convicted of the murders.
Subsequent studies and experiments resulted in finding a pattern of antibody-antigen reactions. Karl Landsteiner from the Institute of Pathological Anatomy in Austria later found that when two different blood types from two different individuals were introduced, they agglutinate. His studies resulted in labeling blood types A, B, AB and O.
The antigens in a human beings blood are called protein markers. These are found on the surface of red blood cells. Antibodies then attach to the antigens. Since an antibody is a protein used to help fight foreign substances, bacteria and viruses, it stands to reason that the antigens are crucial to our existence.
They are effective by clumping to a foreign antigen that may have entered our bloodstream by way of a foreign antibody. If a forensic scientist is attempting to detect a foreign blood type or even species type, they will inject a specific protein into the blood expecting it to clump. This also occurs when the blood type of one individual is introduced to the blood type of another.
The Uhlenhuth Test was the first test developed to help forensic scientists detect the existence of a foreign blood substance. It was instrumental in helping to show where a foreign antigen was present. This has helped forensic investigators to find and convict many suspects of crimes over the last century. Because the antibody is specific to the antigen, it will only implicate where applicable, narrowing the list of usual suspects.