Allogeneic transplantation is a medical procedure where a patient receives stem cells or bone marrow from a genetically different donor. This type of transplant is often used to treat various blood disorders, including leukemia and lymphoma. The donor can be a relative or an unrelated person who matches the patient's tissue type. The main goal of allogeneic transplantation is to replace damaged or diseased bone marrow with healthy cells from the donor. This can help restore the body's ability to produce blood cells and improve the patient's overall health. However, it also carries risks, such as graft-versus-host disease, where the donor's immune cells attack the recipient's tissues.