Transplant rejection | EPFL Graph Search

Transplant rejection occurs when transplanted tissue is rejected by the recipient's immune system, which destroys the transplanted tissue. Transplant rejection can be lessened by determining the molecular similitude between donor and recipient and by use of immunosuppressant drugs after transplant. Transplant rejection can be classified into three types: hyperacute, acute, and chronic. These types are differentiated by how quickly the recipient's immune system is activated and the specific aspect or aspects of immunity involved. Hyperacute rejection is a form of rejection that manifests itself in the minutes to hours following transplantation. It is caused by the presence of pre-existing antibodies in the recipient that recognize antigens in the donor organ. These antigens are located on the endothelial lining of blood vessels within the transplanted organ and, once antibodies bind, will lead to the rapid activation of the complement system. Irreversible damage via thrombosis and subsequent graft necrosis is to be expected. Tissue left implanted will fail to work and could lead to high fever and malaise as immune system acts against foreign tissue. ABO-incompatible transplantation Graft failure secondary to hyperacute rejection has significantly decreased in incidence as a result of improved pre-transplant screening for antibodies to donor tissues. While these preformed antibodies may result from prior transplants, prior blood transfusions, or pregnancy, hyperacute rejection is most commonly from antibodies to ABO blood group antigens. Consequently, transplants between individuals with differing ABO blood types is generally avoided though may be pursued in very young children (generally under 12 months, but often as old as 24 months) who do not have fully developed immune systems. Shortages of organs and the morbidity and mortality associated with being on transplant waitlists has also increased interest in ABO-incompatible transplantation in older children and adults.