Organ transplantation across the blood group barrier has grown immensely in clinical importance since kidney transplant surgeons, Maurice Slapak, Guy Alexandre, and others, made their initial independent attempts to overcome it in the mid-1980s ^[1-4]. That hyperacute rejection could occur when the ABO barrier was crossed had been discovered inadvertently by Hume,Starzl and others during their pioneering efforts to establish kidney transplantation in the 1950s and 1960s ^{[5, 6]}. Thereafter surgeons took pains to avoid ABO-incompatibility.

The topic proved not only important in kidney transplantation, but also in the transplantation of other organs ^{[7, 8]}, with the possible exception of the liver ^{[9, 10]}. Indeed, the first heart transplant might have been carried out by Richard Lower and his colleagues at the Medical College of Virginia before that of Christiaan Barnard in Cape Town, but the opportunity was declined because the donor was found to be ABO-incompatible with the recipient (Lower R, personal communication) .

During the past two decades, however, great efforts have been made to overcome this barrier,largely by (i) reducing the blood level of existing antibodies directed against the donor AB blood type and (ii) suppressing production of new anti-AB antibodies ^[11]. These efforts have proved immensely successful, and, although there remains perhaps a higher risk of early graft loss, today organ transplantation across this barrier is carried out with long-term results comparable to those of ABO-compatible transplantation.

From these studies the concept of ‘accommodation’ developed ^[12-14], and evidence was put forward by West and her colleagues for the development of B cell tolerance in infants with ABO-incompatible heart grafts ^{[15, 16]}. They also stimulated the study of the structure of the ABO oligosaccharide antigens ^{[17, 18]}, and their distribution in the major organs ^{[19, 20]}.

It is to these efforts that this book is primarily directed. The editor, Professor Yi Wang,is himself a pioneer in China of the techniques involved in overcoming the ABO barrier and so is ideally suited to edit such a book. The contributors to the book have covered the field comprehensively, presenting an overview of all aspects of the topic from the history of its pioneering efforts and its pathobiology through to all aspects of its clinical status today. Chapters explore the topic from a general scientific perspective to in-depth discussions of how it impacts transplantation of each of the major organs.

Today, with the increasing use of living kidney and liver donors who may be ABO-incompatible with the intended recipient, the management of ABO-incompatibility is a subject that all transplant surgeons and physicians and allied staffs need to understand. The publication of this book, therefore, is timely as it will provide all those involved with organ transplantation with knowledge of this increasingly important subject. I congratulate Professor Wang on making so much information available to the transplant community.