Chimeras

Stanford University Is Creating Human-Sheep Hybrids for Organ Transplant

Scientists at Stanford University grew embryos containing both sheep and human cells, creating a human-sheep hybrid, paving the way for organs to be grown in animals for transplant in humans. The next step is to implant human stem cells into sheep embryos which have been genetically modified so they cannot grow a pancreas, in the hope that human DNA will fill in the missing code. Critics warn that humans will likely reject the organs because the blood vessels will be sheep-derived, which will trigger the immune system to reject the organ.