41. Transplantation immunology. Immune response in graft rejection. Graft versus host reaction.

Understanding Transplantation

• Transplantation refers to the process where a severely damaged body part is replaced by a healthy organ or tissue taken from another source.
• The part that is transplanted is called a graft or transplant.
• The organism providing the graft is known as the donor, while the one receiving it is called the recipient or host.
• Although considered a last-resort treatment in many cases, transplantation has become increasingly important due to its life-saving potential.

Types of Grafts Based on Source

• Autograft is a graft taken from one part of an individual's body and transplanted to another part of the same body. These grafts are always accepted because they are genetically identical to the host.
• Isograft occurs between two genetically identical individuals, such as identical twins. These grafts are also accepted by the host immune system.
• Allograft refers to a graft taken from another individual of the same species who has a different genetic makeup. This is the most common type and is typically rejected unless special measures are taken.
• Xenograft is a graft taken from a different species. These are highly immunogenic and carry risks that are not fully understood. Porcine heart valves are one exception that are often used, but most xenografts are currently not suitable for human transplantation.