Blood and Allergy. Signs of Manifestation

The body's mechanism of immunity is not always utilized in a manner which seems to us to be beneficial. The body can develop the ability to produce antibodies against any foreign protein, even some which might be thought to be harmless. Once the body is "sensitized" in this fashion, it will react to contact with the protein in various distressing ways—swollen mucus membranes in the nose, overproduction of mucus, coughing, sneezing, watering of the eyes, contraction of the bronchioles in the lungs ("asthma").

In general, the body has an "allergy." Quite commonly, the allergy is to some food component, so that the sufferer will break out in itchy blotches ('hives") if he is not careful with his diet, or he will react to plant pollen and will suffer from the misnamed "hay fever" at certain times of the year.

Since antibodies will be formed against the proteins of other human beings (even these are sufficiently alien), it follows that each human being (multiple births excepted) is a chemical individual. It is not practical, for that reason, to try to graft skin, or some organ, from one person to another. Even where infection is prevented by modem techniques, the patient receiving the graft develops the antibodies necessary to fight it off. This is analogous to the difficulties of transfusion, but with the problems much intensified, for human tissues cannot be classified into a few broad types as human blood can.

This is unfortunate, for biologists have learned to keep portions of the body alive for periods of time. A heart removed from an experimental animal can be kept beating for a while without much trouble and, in 1880, the English physician, Sydney Ringer (1834-1910), developed a solution containing various inorganic salts in the proportions usually found in blood. This would act as an artificial circulating fluid to keep an isolated organ alive for quite respectably long periods.

The art of keeping organs alive by means of nutrient solutions of the proper ionic content was developed to a fine art by the French-American surgeon, Alexis Carrel (1873-1944). He kept a piece of embryonic chicken heart alive and growing (it had to be periodically trimmed) for over twenty years.

It follows then that the possibility of organ transplantation, when such an organ is required to save a life, would be bright, were it not for the adverse antibody response. Even so, some transplantations, such as the cornea of the eye, can be made routinely, while, in the 1960s, successful kidney transplants have occasionally been managed.

In 1949, the Australian physician, Frank Macfarlane Burnet (1899- ), suggested that the ability of an organism to form antibodies against foreign proteins might not be inbom after all, but might develop only in the course of life; though perhaps very early in life. An English biologist, Peter Brian Medawar (1915- ), tested the suggestion by inoculating the embryos of mice with tissue cells from mice of another strain (without recent common ancestors). If the embryos had not yet gained the ability to form antibodies, then by the time they reached independent life and could form them, it might be that the particular foreign proteins with which they had been inoculated would no longer seem foreign. This turned out, indeed, to be the case, and in adult life, the mice, having been inoculated in embryo were able to accept skin grafts from a strain where, without inoculation, they would not have been able to do so.

In 1961, it was discovered that the thymus gland, hitherto not known to have any function, was the source of the body's ability to form antibodies. The thymus produces lymphocytes (a variety of white blood corpuscle) whose function it is to form antibodies. Shortly after birth, the lymphocytes produced by the thymus travel to the lymph nodes and into the blood stream. After a while, the lymph nodes can continue on their own and at puberty, the thymus gland, its job done, shrivels and shrinks to nothing. The effect of this new discovery on possible organ transplantation remains to be seen.