For aplastic anemia, 80-90 % of patients can make a full recovery. But bone marrow transplants are limited by the degree of matching of HLA, a critical defense mechanism in the immune system that helps the body distinguish between friend and foe. Unless the donor and the recipient have a complete match, the result will be rejection of the transplant.
但骨髓移植卻受限於「人類白血球抗原」的吻合度，白血球抗原是人體內鑑別敵我、以啟動免疫能力的重要防衛機轉，若捐贈與受贈者間未能完全吻合，就會產生排斥現象。