Transplantation of organs between species

The shortage of organs from human donors for transplantation has stimulated a renewed interest in the use of organs from animals or xenografting. Such grafts can be transplanted between closely related species--concordant, or distantly related species--discordant. In this mini review the immune processes which cause rejection for each of these categories is described. Data demonstrating methods by which this rejection can be controlled are summarised and a possible approach to clinical application is described.