Purpose of review
Understanding the mechanisms involved in immune protection provided by a hepatic allograft is imperative as further therapies for highly sensitized patients could be developed and thus expanding the donor pool and improving outcomes.
The clinical data from immune protection comes mainly from combined liver and kidney transplants with excellent results in overall survival and also that of the allograft. This phenomenon has also been observed in dual liver transplants with heart, lung, skin and intestines, albeit with less data. In heart transplant recipients, the liver allograft has proven to be protective even in cases of highly sensitized patients with at least equal survival and rejection outcomes to recipients of heart alone. Although not fully understood, the mechanisms for immune benefit proposed are extensive at different levels of the hepatic immune system. Some of these mechanisms include chimerism, T-cell deletion, the presence of peripheral regulatory T cells and donor-specific antibody neutralization.
Combined heart and liver transplantation is an infrequent but growing procedure due to increasing need in the adult congenital heart disease and cardiac amyloid populations. Given the ever expanding need for heart transplantation, understanding immunological phenomena that could expand the donor pool could, subsequently, increase the number of transplants.