Acquisition of immunological self-recognition by the fetal rat.

Rats in which normal development of the thyroid gland had been interrupted by the injection of 131I during fetal life are liable to mount autoimmune responses against grafts of syngeneic thyroid tissue transplanted in adult life. Although autoimmune thyroiditis developed spontaneously in grafted tissue, the recipients' own thyroid glands remained free from autoimmune changes, showing only irradiation damage. Other syngeneic endocrine grafts transplanted to these rats were not susceptible to autoimmune attack. This experiment demonstrates that contact of self-determinants with the developing mammalian immune system is required if autoimmunity is to be prevented.