Transplantation refers to the process of moving cells, tissues or organs from one part of the body to another, whether within the same person, or between a donor and a recipient. It is usually a life-saving intervention and is a major operation. However, the transplanted tissue or organ may be rejected by the immune system. Rejection is an adaptive immune response of the body that can occur due to the mechanisms of cellular immunity or humoral immunity. Different transplanted tissues favor different rejection mechanisms. Acute rejection occurs in all transplants unless immunosuppression has been achieved. An exception to this is transplantation between identical twins. Hyperacute rejection response sets in within minutes after a transplant, which if unattended may trigger a systemic inflammatory response syndrome. Rapid clumping, particularly the agglutination of red blood cells, is a common risk in kidney transplants. Chronic rejection can arise when there is a long-term loss of function in the transplanted organ. This loss in function arises due to fibrosis of the blood vessels of the transplanted tissues. This is responsible for the long-term morbidity witnessed in lung-transplant recipients. Transplant rejection can be lowered by using immunosuppressant drugs after transplantation and by prior determination of the molecular similitude between donor and recipient. This book provides comprehensive insights into the field of transplantation immunology. It presents researches and studies performed by experts across the globe on the methods and protocols of transplantation. It is a vital tool for all researching and studying this field.