Traces of blood can provide forensics with information about the person's age. Picture: Xenia B. /
Reading a blood sample could be enough for a forensic doctor in the near future to determine the age of humans: Dutch scientists have developed a method based on the examination of immune cells in the blood. In the first tests, the new method was successful in dividing the persons from whom the blood samples originated into age categories of 20 years each. Although the accuracy is thus significantly lower than that which can be achieved with the help of bone - especially teeth often allow a very accurate assessment with only a few years deviation. Nevertheless, the researchers estimate their discovery as very significant: In many crimes there are simply no bones available, but blood stains - from the perpetrator or missing persons and potential victims of violence. Manfred Kayser from the Erasmus MC University Medical Center Rotterdam and his colleagues present the new method The basis of the procedure are the so-called T lymphocytes, T cells for short. These are part of the white blood cells and are an important part of the immune system: With the help of special receptors that are on their cell surface, they examine foreign cells and classify the stranger as a friend or foe. In the latter case, they then set the body defense in motion.

Investigating the invaders is done by attaching the T cells with their docking to characteristic protein structures of the stranger, the so-called antigens. In order for as many different strangers as possible to be recognized, the T cells must have correspondingly many different receptors. They achieve this through a constant remodeling of their genetic material. In the process, so to speak as rejects, small circular DNA fragments are formed, which are called sj-TRECs for short.

Their number decreases continuously with the age of human beings. The scientists use this fact: they determine the sj-TREC content of a blood sample and compare the result with standard values ​​that they previously determined using samples from various persons of known age. From this they deduce the age of the unknown person. The researchers estimate that the new method could soon find its way into forensic practice.

Manfred Kayser (Erasmus MC University Medical Center, Rotterdam) et al .: Current Biology (DKfZ), Vol. 20, No. 22 dapd / Mascha Schacht advertisement


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