午夜福利1000集合

YOU may have left a bigger impression on your mother than you thought. Many women carry around their offspring鈥檚 DNA for the rest of their lives, say Italian researchers. Most of the time it goes unnoticed, but occasionally this foreign DNA can trigger life-threatening diseases.

Cells from a fetus are already known to persist in the mother鈥檚 body for decades after the child is born (New Scientist, 24 February 2001, p 8). The cells can lodge in lymph nodes, liver, spleen or muscle, and may eventually form part of the mother鈥檚 tissue.

But now a team led by Pietro Invernizzi at the University of Milan has astonished other researchers with the discovery of fetal DNA in the blood of women up to 60 years after they gave birth. 鈥淚 was kind of bowled over,鈥� says Carol Artlett at Thomas Jefferson University, Philadelphia, who studies fetal cells that remain in a mother鈥檚 body.

Invernizzi looked for Y-chromosome sequences, which are present only in males, in the blood of 160 women who had given birth to at least one son. The results were positive for about 30 of the women, many of whose sons were several decades old. No Y sequences showed up in 50 women who had never had a child. Invernizzi thinks that fetal stem cells embedded in the mothers鈥� tissues keep dividing, and shed DNA into the bloodstream when they break down.

Fetal cells have been blamed for autoimmune diseases such as scleroderma, a rare and sometimes fatal condition. Artlett thinks that the fetal cells mount an immune response against the mother鈥檚 own cells, although the details remain a mystery.

The research also casts doubt on plans to test for inherited diseases in fetuses by looking for fetal cells in the mother鈥檚 blood. If the mother has already had one child, it would be difficult to tell which baby鈥檚 DNA you are looking at, says Invernizzi.