Rejection of cardiac xenografts by NK cells and macrophages

Abstract

DUE TO the nature of hyperacute rejection of xenografts transplanted between phylogenetically disparate species, cellular immune responses in xenotransplantation are less well understood. Recent advances in controlling hyperacute rejection have allowed the survival of vascularized xenografts to the point where these may elicit cellular immune responses. There is increasing evidence showing that, if hyperacute rejection is circumvented, discordant xenografts may undergo rejection within a few days. This delayed xenograft rejection is immunopathologically characterized by a prominent cellular infiltration consisting of mainly natural killer (NK) cells, macrophages and T cells. 1,2 In the present study, the role played by NK cells and macrophages in xenograft rejection was further studied in athymic nude rats receiving concordant xenografts. As these nude rats were previously shown to have strong NK cell activity, we were interested to see how this would influence the capacity of these T-deficient rats to reject hamster heart xenografts.