A Model System for Determining Histocompatibility

Of the many factors that may be significant in permitting successful homotransplantation of tissue and organs, there is little question that the genetic relationship of the donor to the recipient will always be of prime importance. In the laboratory animal, there are many methods of producing permanent or markedly prolonged survival of homografts when major histocompatibility gene loci are the same. In every instance, however, when there is a major genetic incompatibility between donor and recipient, a much more intensive attack is required to accomplish any prolongation of homograft survival. In the human, this is equally true. Where sublethal irradiation and uremia are the two major variables affecting homografts, the only permanently successful kidney transplant that we have been able to perform has been between nonidentical twins of the same sex (1). These men had 26 identical blood groups, and there was a 26-day survival of skin on the healthy donor from the sick recipient. There is little doubt that the inherent compatibility in this donor-recipient pair was as significant for success as the other maneuvers that were carried out. We believe that a constant search for methods of assessing histocompatibility in humans must accompany the extensive efforts to permit homograft survival in the animal. Working with normal human volunteers over the past few years, our clinic has demonstrated that a) skin homograft rejection will induce a