The terrible constraint on organ transplantation is that every life extended depends on the death of someone young enough and healthy enough to have organs worth transplanting.

Literally, the ability of different tissues to "get along"; strictly, identity in all of the transplantation proteins, which is a requirement for the prevention of graft or organ rejection.

Rarely, rabies may be contracted by inhalation of virus-containing aerosol or via transplantation of an infected organ.