REJECTION OF DISCORDANT NEOVASCULARIZED XENOGRAFTS - IS IT SIMILAR TOTHE RESPONSE AGAINST METAZOAN PARASITES

Allotransplantation is now widely successful but is increasingly limit ed by a shortage of human organ donors. Xenografts could solve this sh ortage but hyperacute rejection due to preformed antibodies that react with graft endothelial cells in primarily vascularized xenografts tha t cannot be controlled with current immunosuppressants causes graft lo ss and negates this approach. In the absence of hyperacute rejection, the host mounts a vigorous cellular response but its nature is poorly understood. In contrast, the cellular immune response against allograf ts is usually reversible with immunosuppression. The anti-xenograft re sponse is similar to that generated against metazoan parasites but the y often survive. Perhaps the host perceives a xenograft in a manner si milar to the recognition of a parasite and reacts in a similar way but with parasites the response is often inadequate. Perhaps there are le ssons to be learnt from parasitology that may be applicable to xenotra nsplantation.