Induction of late-onset spontaneous autoimmune thyroiditis by a single low-dose irradiation in thyroiditis-prone non-obese diabetic-H2h4 mice.

The previous data regarding the effect of irradiation on thyroid autoimmunity are controversial. We have recently reported the exacerbation of autoimmune thyroiditis by a single low dose (0.5 Gy) of whole body irradiation in thyroiditis-prone non-obese diabetic (NOD)-H2(h4) mice treated with iodine for 8 weeks. However, it is uncertain in that report whether the results obtained by the provision of iodine in a relatively short period of time (8 weeks) accurately reflects the long-term consequences of low-dose irradiation on thyroid autoimmunity. Therefore, we repeated these experiments with mice that were monitored after irradiation without iodine treatment for up to 15 months. We found that a single low-dose (0.5 Gy) irradiation increased the incidence and severity of thyroiditis and the incidence and titers of anti-thyroglobulin autoantibodies at 15 months of age. The numbers of splenocytes and percentages of various lymphocyte subsets were not affected by irradiation. Thus, we conclude that low-dose irradiation also exacerbates late-onset spontaneous thyroiditis in NOD-H2(h4) mice; one plausible explanation for this may be the acceleration of immunological aging by irradiation.