Experimental allergic thyroiditis produced in strain 13 histocompatible guinea pigs after a single immunization with thyroid extract and Freund's adjuvant was followed for more than 2 years. The disease appeared as early as 5 days and persisted for the entire period studied, although it regressed in the later stages.
Circulating antithyroid antibody was detected at low levels as early as 7 days after immunization, and increased to a peak at the time of most severe disease. Thereafter, antibody decreased, but was still detectable in most animals as late as 2 years. There was no correlation between antibody levels and extent of disease except at the 7 week stage.
Delayed sensitivity to thyroid antigen was found as early as 5 days after immunization, and appeared to precede the development of thyroiditis in many animals. It correlated closely with thyroiditis at 5 days and 7 weeks. At 6 months, the delayed skin reaction was decreased, and a modified type of reaction appeared which persisted as long as 26 months.
The time relationship of delayed sensitivity, thyroiditis, and circulating antibody continue to confirm the role of delayed sensitivity in the pathogenesis of this disease. The accumulated data demonstrating production of thyroiditis without antibody, and the converse, tend to strengthen this view.
