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Foreign invaders

发布时间:2019-03-07 03:19:03来源:未知点击:

By Philip Cohen, San Franciso From the annual meeting of the American Association for the Advancement of Science in San Francisco Two generations of “foreign” cells in a mother’s body could be a trigger for autoimmune diseases such as rheumatoid arthritis and multiple sclerosis. The discovery may explain why women are far more likely to develop these illnesses than men. The first foreign cells are picked up when a fetus shares blood with its mother. When that fetus is born, grows up and becomes an expectant mother herself, a second set of cells infiltrate from her own unborn baby. Autoimmune diseases cause the body’s defence mechanisms to attack itself and J. Lee Nelson, at the Fred Hutchinson Research Center in Seattle, Washington, wanted to understand why three times more women are affected than men. The symptoms of the diseases tend to appear during and after reproductive years and Lee suspected that fetal cells might be a trigger. So her team examined mothers with an autoimmune disease called systemic sclerosis. As she suspected, the women with sclerosis had 20 times more fetal cells in their blood than those without the disease. Startlingly, the fetal cells persisted in the mother’s blood for decades after the birth. Her lab then examined surface proteins on the fetal cells called HLAs, which the immune system used to distinguish its own cells from others. They found that if the mother matched some of her child’s HLA, it actually increased her risk for the disease nine-fold. She thinks this is because the cells escape immediate destruction by the immune system, only to trigger a self-directed attack later on. But Nelson realised that a mother might also harbour cells from her own mother, setting up a possible three-generation clash of HLA types. Indeed, her new work presented at the AAAS, shows that a close match of HLA between grandmother and child further increases the risk of disease risk. This suggests that the two types of cells somehow co-operate to trigger problems in the immune system. “It’s a war across generations that takes its toll on the body,” says Nelson. She adds that, in the era of massive human DNA sequencing projects, there is an important lesson to be drawn from her work: