Why is a patients body less likely to reject an allograft if it comes from a close relative?

A patient's body is less likely to reject an allograft from a close relative due to the increased genetic similarity between the donor and recipient. Close relatives share more human leukocyte antigen (HLA) markers, which are crucial for the immune system to recognize self versus non-self. This compatibility reduces the likelihood of an immune response against the transplanted tissue, leading to better acceptance and integration of the allograft.