What are the problems with xenografts?
As with allografts, the major problem is with rejection. Humans have “natural antibodies” that circulate in the blood and cause immediate graft failure when organs from some species are transplanted (for example pig organs). Also, a system of proteins in the body called “complement” are activated whenever pig organs are transplanted into primates, leading to severe systemic toxicity. This may be because the primate complement regulatory systems do not recognize the porcine complement. Genetic engineers are trying to get around this problem by genetically modifying pigs so that they have some complement regulatory proteins on their cells.
