What does it mean and how is xenotransplantation?

In a xenotransplantation is the transmission of life and functional cells or groups of cells (including whole organs or body parts) between different species.
Inform the allotransplantation is demarcate where the transfer between genetically different individuals of the same species is performed.


By the limited availability of donor organs for allotransplantation, xenotransplantation promises to be a possible alternative. Heart valves from pigs are used today as an alternative to mechanical. Here, the heart valves are not edited so that they bear no antigen on the surface that could be recognized as foreign. However, to this day whole organ xenotransplantation in humans are not possible.
Although primates are much more closely related to humans, pigs are traded today as the most promising option for organ transplants. Pig organs are physiologically more suitable to satisfy the requirements of the human body. The first cardiac xenotransplantation in a person with a chimpanzee heart showed that the heart was too small to maintain the circulation of blood (Hardy, Mississippi, 1964). Pig hearts however have adequate function of the left ventricle to keep a human being alive and are also small enough to fit into the thorax.

Hyperacute rejection

The first stage of the rejection takes place within the first 24 hours. Here already formed antibodies are directed against the endothelial cells of the implant. Through the addition of these IgG antibodies leads to complement activation, swelling of the endothelium and microvascular thrombosis.
The coming into effect here antibodies directed against Galα1, 3Galβ1, 4GlcNAc (αGal) carbohydrate side chains of the endothelial cells of the pig. These side chains are located on the endothelial cells of non-primate mammals and New World monkeys and are not present in humans and Old World monkeys. From natural infections of the gastrointestinal tract with αGal expressing microorganisms, the human body is very early antibodies against these carbohydrates. To avoid that kind of rejection, succeeded 2002, a so-called co-pig (αGal - / -) to generate for this carb, with the next phases of rejection could be achieved.

Risks and ethical concerns

The biggest concern in the use of xenografts, the risk of transmitting animal pathogens to the host and to all humanity. It has been observed that endogenous porcine retroviruses (PERVs - porcine endogenous retrovirus) to be transferred to human cell lines [3] However, there is still no proof that this can also happen in vivo in [4] There are several ethical concerns.. xenotransplantation. Unlike all other medical procedures here called a chimera is formed, containing the living cells from two different species. [5] Also, from a religious perspective, there are different concerns. At the XVIII International Congress of the Transplantation Society in Rome in 2000 by Pope John Paul II has approved the use of pigs as organ donors.
Xenotransplantation of human tissue, such as tumor cells in laboratory animals - especially nude mice - (called xenografts) since 1972, is an established method in preclinical research.