Rejection (Allograft Rejection)

Allograft rejection occurs when a person’s immune system recognizes a transplanted organ or tissue as foreign and attacks it. This response is similar to how the body defends against infections, but in this case, it mistakenly targets the new organ. Rejection can happen at different times—early or later after transplant—and may cause symptoms like pain, swelling, or organ dysfunction. To prevent this, recipients usually take medications that suppress their immune response, helping the body accept the new organ and reducing the risk of rejection.