Organ rejection occurs when the body's immune system identifies a transplanted organ as foreign and attacks it. This can happen after procedures like a kidney transplant or heart transplant. The immune system's response can lead to inflammation and damage to the new organ, making it less effective or even causing it to fail. To prevent organ rejection, doctors often prescribe immunosuppressant medications. These drugs help suppress the immune response, allowing the body to accept the new organ. Regular check-ups and monitoring are essential to ensure the organ is functioning well and to adjust medications as needed.