Transplantation immunology is the study of how the immune system responds to transplanted organs or tissues. When a donor organ is placed into a recipient, the recipient's immune system may recognize the new tissue as foreign and attempt to reject it. This response is primarily mediated by T cells and antibodies, which can target the transplanted cells. To prevent rejection, doctors often prescribe immunosuppressive drugs that help dampen the immune response. These medications allow the body to accept the new organ while increasing the risk of infections and other complications. Understanding transplantation immunology is crucial for improving transplant success rates and patient outcomes.