The concept of using encapsulation for the immunoprotection of transplanted cells was introduced for the first time in the 1960s. "[Microencapsulated cells] might be protected from destruction and from partici- pation in immunological processes, while the enclosing membrane would be permeable to small molecules of specific cellular product which could then enter the general extracellular compartment of the recipient. For instance, encapsulated endocrine cells might survive and maintain an effective supply of hormone." (Chang, Ph.D. Thesis, McGill University, 1965; Chang et aI., Can J Physiol PharmacoI44:115-128, 1966). We asked Connaught Laboratories, Ltd., in Toronto to put this concept into practice. In 1980, Lim and Sun from Connaught Laboratories reported on the successful implantation of poly-I-Iysine-alginate encapsu- lated rat islets into a foreign host. [Lim and Sun, Science 210:908-909, 1980]. Now many groups around the world are making tremendous progress in the encapsulation of a multitude of cell types. Kiihtreiber, Lanza, and Chick have invited many cell encapsulation groups from around the world to contribute to this book. The result is a very useful reference book in this rapidly growing area. With so many excellent au- thors describing in detail the different areas of cell encapsulation, my role here will be to briefly discuss a few points.

The majority of patients in need of organ transplants do not survive long enough for a suitable human organ to become available. Xenotransplantation, the transplant of animal organs into humans, has attracted substantial media attention. If, as appears likely, it proves possible to "humanize" animal organs and evade the problems of rejection, in the coming few years there will be a tremendous increase in this procedure, mostly using organs from animals specifically for their harvestable organs. This book will lay out the potential and promise of the technique, the history of organ transplantation, the technical problems and breakthroughs in overcoming immune rejection, and typing and humanizing donor organs for transplantation. The ethical question of growing animals specifically for organ harvest, and the substantial public health concern from the certainty that animal viruses will pass into humans with the donated organs, will be fully discussed. The authors are among the leaders in the field of Xenotransplantation.