Five cloned piglets, genetically modified so that their organs are much less likely to be rejected by a human donor recipient, have been born in the US. 在美国已诞生了5只基因改良的克隆小猪,这使得它们的器官在植入人体时产生排异反应的可能性大为缩小。 More than 62,000 people in the US alone are waiting to receive donated hearts, lungs, livers, kidneys and pancreases. The number of human donors falls far short of demand. Pig organs are of a similar size to human organs, and some scientists hope they might be used to help meet the shortfall. But previous attempts to transplant unaltered pig tissue into humans have failed, due to immune rejection of the tissue.