xenotransplantation

Xenotransplantation is transplanting living organs, tissue, or cells from one species into another — most famously, putting an organ from an animal into a human. The idea is to ease the chronic shortage of human donor organs: many more people need a kidney or a heart than there are donors, and an animal source could, in principle, be available on demand. Pigs are a leading candidate because some of their organs are close to human size.

The body's biggest objection is the immune system, which is built to attack anything it reads as foreign — and a whole animal organ screams 'foreign'. So researchers gene-edit the donor animals, switching off pig genes that trigger rejection and adding human ones to calm the immune response. Surgeons then transplant the organ much like a human one and use strong medicines to keep the recipient's immune system from destroying it.

This matters because it could one day relieve long transplant waiting lists, and the first experimental human cases have happened. But it is still early and risky. The two great hurdles are rejection — the body may attack the organ despite every precaution — and infection, the worry that an animal virus could cross into people. It is a frontier under careful study, not a routine option.