Xenotransplantation: recent progress and current perspectives.

A severe shortage of human transplant donors has sparked interest in the use of animals as a source of organs and tissues for transplantation. Clinical application of xenotransplantation is limited in large part by the severe immunological reaction of the recipient against the graft. This immunological reaction is mediated initially by components of natural immunity such as xenoreactive antibodies, complement and natural killer cells and later by elicited humoral and cellular immune responses which act in concert to disrupt the function of the endothelial lining of blood vessels. The past few years have brought considerable progress in elucidating the molecular and cellular basis of xenograft rejection and in developing strategies to overcome xenograft rejection.