Characterization of the human antiporcine immune response: a prerequisite to xenotransplantation.

Successful xenotransplantation necessitates solving problems of hyperacute rejection and understanding the cellular immune responses that occur. Considerable progress has been made in our understanding of the molecular genetic basis of the rapid hyperacute antibody-mediated rejection mechanisms that occur in xenogeneic organ rejection. In parallel, strategies involving the use of transgenic animals expressing complement inhibitors are beginning to offer encouraging evidence that hyperacute rejection can be overcome. A greater understanding of cell-mediated immune interactions is now required to achieve long-term xenograft survival. Current studies are focused on T cell receptor (TCR)/major histocompatibility complex (MHC) and costimulatory signals that activate human CD4 and CD8 T cells.