Mind and Body
Alien Admissions
By JOHN LYDGATE It was an ancient observation that certain fevers never attacked twice. In the eighteenth century, Edward Jenner; a country doctor, ex- ploited this observation and deliberately induced a mild form of smallpox (actually cowpox) in a successful attempt to prevent more serious attacks of the disease. It was a case of protection by a hair of the dog which might bite. The mechanism of the immunity remained obscure until the end of the nineteenth century when the work of Pasteur, Ehrlich and many others showed that immunity was only a special example of the animal's general Behaviour towards foreign materials. The vaccination alerted the organism by putting the foreign sub- stance into a sort of chemical rogues' gallery long in advance of the crime.
However, the very notion of foreignness, of credentials, argues accurate self-knowledge on the part of each organism, a knowledge which allows the organism to distinguish between stuff which is 'self' and other stuff which is foreign or 'non- self.'' The prize-winning work of Professor 'Reconstructions of her Ladyship by Buffet, Picasso, Annigoni and the Liverpool Police.' Medawar and his associates at University Col- lege has shown that this discrimination is ex- tremely refined and that the organism dis- tinguishes material, not merely from another species, but also from another individual of the same species. The rogues' gallery includes, it would seem, a fingerprint collection. Medawar showed this by using skin grafts taken from one animal and transplanted to another. Unless the two animals were identical twins the grafts were rejected after a while. The creature's cells had accurately diagnosed the graft as something not 'self' and produced antibodies to the alien tissue.
This biological xenophobia is not strictly congenital. During the intra-uterine period of development the organism is biochemically gullible. It has only a diffuse sense of its own chemical identity and during this period it seems, from the experiments, to be compiling an inven- tory of its own characteristics so that in the future it will have an identity card against which to check the credentials of an invader. During this gullible phase the creature's cells will accept a foreign protein and include it in the bio- chemical roll-call of its own features. In this way Medawar and his colleagues were able to cheat the animal into accepting a foreign skin- graft in later life.
Once the animal has left the womb, or at least a few weeks later, it no longer accepts appli- cants for membership of its own protein identity. From this date any other protein which does not appear on this list is recognised as a foreigner and the inexorable antibody machine is set in motion. While this has clear advantages in the field of bacterial immunity it provides a serious drawback for the plastic surgeon and others interested in treating diseases by replacements of diseased and damaged organs. Until now such grafts have always failed, the patient's cells pig- headedly refusing to modify their policy of dis- crimination and allow the foreign graft to take. Various techniques have been used recently to bind and gag this antibody system in an attempt to get grafts to take. Exposure to a sub-lethal dose of radiation temporarily stifles the antibody machinery until the new tissue can gain a foothold. It was hoped that the irradiation would so muddle the chemical memory of the self-recogniser system that when it recovered it would welcome the graft as a long-lost piece of 'self.' Unfortunately the memory is perversely stable and once the creature has recovered from the dose of X-rays it soon turns the graft out of doors.
Just occasionally, however, this memory does fail. It does so in a very peculiar way, though. It is not that it fails to recognise foreign proteins as such. It seems to forget items of its own identity so that parts of the animal's own body are quite suddenly treated as foreign material. These diseases are called auto-immune and the idea is now one of the most fashionable 0 medical practice. One of the first to _ be recognised, Hashimoto's disease, affects the thyroid so that it swells up and becomes hard and functionless. The disease has been known for many years but until recently was put down to a form of non- specific inflammation. Some brilliant work at the Middlesex Hospital has shown that the condi- tion is due to a sudden failure of recognition. Tho thyroid is, as it were, cut dead by the other cells of the body, treated as if it did not belong and rejected exactly as if it were a foreign skin graft.
As research in this field expands it bec.'mes clear that quite a number of previously per- plexing diseases are examples of such incom- plete self-knowledge. How can such lapses occur? One way is known at least. Early in develop- ment, a tissue may become insulated from the rest of the circulation and so inaccessible at the time when the roll-call of 'self' substances is called. The lens of the eye is just such a tissue. Locked away in the watery cell at the front of the eyeball it escapes from the identity parade so that when the creature has completed its de- velopment the inventory of 'self' substances does, not include those which make up the lens of the eye. So long as the lens remains in its isolated cell all is well. Occasionally, however, when the eye is injured some of the lens protein escapes into the blood-stream where it is immediately regarded as a foreign invader. Antibodies to the lens substance are released, pass via the blood- stream to the other eye and destroy the intact lens in a disease called sympathetic ophthalmia.
Of more profound interest is the way in which the organism first compiles its menu of 'self.' How is the list coded? Such issues are right down on the grass 'roots of basic biology. Implicit in the answers are the solutions to the problems of biochemical politics: the problem of the political constitution of cells; the organic charter which determines that creatures are the orderly re- publics which we know rather than the turbulent Congos which they might be.
The backs of our hands, which we claim to know so well, would appear to contain mysteries undreamt of in our present philosophy.
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