Renal homotransplantation in identical twins.

This is a report of the successful kidney transplantation from one identical twin to another with good renal function persisting after 9 months. Previous attempts at renal homotransplantation both clinically and experimentally had been unsuccessful, with the one exception between di-zygotic bovine twins in which a kidney transplant has survived and functioned for over a year. Success in that instance presumably resulted from the production of an acquired mutual tolerance to each other’s tissues by the mingling of fraternal protein in the common placental circulation.1 In all other instances, failure of the transplanted kidney occurs by what appears to be an immune, or “antigen-antibody-like,” reaction between donor tissue and recipient. The microscopic pattern of the rejected kidney indicates that the homograft itself is actively reacting against the recipient to a greater degree than had been suspected by earlier investigators.2,3 Transplantation of kidneys in dogs rarely maintain function for more than 10 to 14 days in spite of vigorous attempts to alter the rejection response.4,5,6 Although human renal homotransplants have functioned for a longer period of time, 1 for as long as 5⁄2 months, permanent survival has not occurred and the clinical and microscopic pattern of rejection is similar to that in the experimental animal.7 There are, however, several experimental observations which made success between identical twins seem likely and justified the removal of a normal kidney from a healthy donor. (1) Immunologic and genetic similarity apparently accounts for the permanent survival of skin homografts between identical twins.8 (2) When skin or kidney homografts are carried out between antigenically dissimilar individuals the early function and the histological picture of rejection of each appear similar.9 (3) Skin and kidney homografts possess a common antigen which can sensitize a recipient to a subsequent homograft of either tissue from the same donor.2,3 This further suggests that skin and kidney grafts might behave similarly. (4) We had established to our own satisfaction that renal autografts had normal function indefinitely in animals. This observation is important because pre-supposing initial success of the transplant between antigenically similar (identical) twins, a second problem to be weighed was the permanency of such function. Lacking reported instances of adequate functional studies in long term renal autografts we observed in our own experiments that permanently successful function of a single life-sustaining renal autograft resulted from the use of a recipient site which allows direct implantation of the ureter into the bladder, which RENAL HOMOTRANSPLANTATION IN IDENTICAL TWINS*