*Regulatory T Cells in the Mosaic of Liver Transplantation Tolerance DOI: http://dx.doi.org/10.5772/intechopen.94362*

accordance with the patient's weight. Choosing a donor candidate is sometimes difficult due to the presence of arterial variations combined with additional abnormalities in other vessels and the biliary tract [6]. LDLT is suitable in cases of rare diseases in patients under 1 year of age. Of the pediatric liver transplantations performed at Lozenets University Hospital, about 65.5% of the patients are in this age group, and between 10 and 18 years of age they are significantly fewer [7].

Another type is domino transplantation, but it is rarely performed. Indication for it is Familial amyloid polyneuropathy (FAP). The disease affects extrahepatic organs and liver function is preserved. This allows the liver of the FAP patient to be given to another patient, from whom (in turn) receives the damaged organ (domino effect) [8]. The main requirement for the FAP recipient is to be over 55–60 years old, in order to minimize the risk of developing the disease.

Partial transplantation is performed as a matter of urgency in two specific situations. The first is in acute liver failure, in order to support the damaged organ until its recovery. The graft is then removed and the immunosuppressive therapy is stopped. The second case is in patients with congenital functional or metabolic disorders that affect the liver. Implantation of the partial graft preserves its own organ, corrects metabolic abnormalities and does not require whole liver transplantation [9]. In both situations, the transplant can be orthotropic or heterotropic.

A variant of the partial transplantation is the split-transplant, in which the two lobes are distributed between two recipients. In recent years, due to the increased number of patients on the waiting list and the small number of potential donors, the technique of split-liver transplantation has been applied in which in vivo /in situ or ex-vivo/ex-situ the liver is divided into two parts - right for adult transplantation and left for pediatric transplantation. In some cases, it is possible to use the split-technique for transplantation of two adults. It is preferable to perform split-LT in-vivo, which reduces the risk of biliary complications, hemorrhage and significantly reduces the cold ischemia time of the graft [4, 5]. The main condition is the ratio between the weight of the graft and the patient, which must be at least 0.8% [4, 10]. The aim is to ensure the long-term vital functions of the recipient.

The complexity of the operation creates preconditions for the occurrence of complications during and after the operation. In the postoperative period, the leading are vascular and biliary complications, stenosis of the anastomosis, risk of infection and others.

In the long term, the outcome of transplantation depends largely on the establishment of optimal post-transplant immune tolerance. Here the immunological features of the liver, which distinguish it from other organs, play a significant role.
