Science
Rejection slips
Bernard Dixon
As with announcements of breakthroughs in cancer research, scientists' claims to have overcome the rejection of transplanted organs should be treated with extreme wariness by newspaper readers, television viewers, and science writers alike. Even setting aside the publicity(i.e. money-) seeking deliberations ot those whose boasts are founded on the most tenuous of evidence, there are enough soundly-based ideas that have been vanquished, enough realistic hopes shattered, to make profound scepticism mandatory towards all new claims. As it is, decades after the surgical aspects of organ grafting were mastered, the body's relentless capacity to attack transplanted tissue remains one of the most intractable problems of medical science. Though kidney transplantation, for example, is now an established, life-saving procedure, the phenomenon of immunological rejection remains unconquered. All we can do is to skate around it or try to ameliorate its damaging effects.
That being so, one must be both optimistic and cautious about a piece of work recently annotteced from the Sloan-Kettering Institute for Cancer Research, New York City. The gist of it is a claim by Dr William Summerlin to have devised a method by which certain types of animal (including human) tissues can be deprived of their capacity to induce rejection when transplanted from a donor to a recipient. Given this treatment during the interval between removal and grafting, 'foreign' tissue is accepted without any adverse reaction—and without recourse to the.drugs that are used clinically to damp down the normally aggressive rejection process in transplant patients.
Summerlin's special treatment is, in essence, extremely simple. He merely grows the tissue artificially for a time in a glass vessel containing a chemically-compounded culture medium. During this period of existence outside an animal body, the tissue changes in such a way that it becomes more acceptable after transplantation. Skin, corneas, and other tissues can be kept viable for up to several months when cultured in this way. As well as drug treatment, present methods of curbing graft rejection entail matching as closely as possible the tissues of the donor and recipient (hence the preference for closely related donors for kidney transplants). Using Summerlin's technique. however, even grossly mis matched tissue 'takes' in its new host after suitable treatment. He claims, for example, that skin can be transplanted between people whose tissues differ considerably. Human skin can also be grafted successfully on to other species—human, pig, guinea-pig and rat skin being accepted by mice. In these cases the foreign tissue retains its own identity: white skin transplanted to a black animal remains white.
these are, of course, only the first results of a lengthy research Programme. They have been greeted with scepticism, largely because similar attempts many Years ago to cross-transplant tissue after a period of artificial growth mostly ended in failure. Some scientists, however, have confirmed Summerlin's results, and the indications are that when failures do occur, they happen because experimenters have not achieved precisely the right cultural conditions for their tissue. Even minor differences here can seriously impair the chances of success.
Such crucial technical details aside, the major potential problem in applying this new knowledge seems to be the difficulty in culturing whole organs (such as kidneys and liver) artificially, compared with the relative simplicity of maintaining cultures of skin cells. Even with this restriction, however, Summerlin's work could be of great importance in providing skin grafts for burn victims. (At present, skin has to be taken from elsewhere on the patient's own body.) If the work proves of Wider application, to all organs and tissues, the implications are indeed staggering.
Previous page
