A fine structure study of passive transfer thyroiditis.

The fine structural changes of passive transfer thyroiditis were observed in guinea-pigs injected intravenously with homologous anti-thyroglobulin serum. Eosinophils and mononuclear cells entered the interstitial area of the thyroid within 1 hour following the infusion of antisera. This cellular reaction reached its maximum intensity at 24 hours following antibody administration. Eosinophils were seen adjacent to and appeared to enter within the cytoplasm of the thyroid epithelial cells. Mononuclear cells ingest many of the eosinophils. Polymorpho-nuclear leucocytes were not present in significant numbers. Platelet aggregates were present in small blood vessels and endothelial cells showed increased pinocytotic activity during this period. This inflammatory reaction subsided rapidly and at 8 days the thyroid glands appeared histologically normal. Passive transfer thyroiditis produced by homologous antithyroglobulin antiserum appears to be an unique experimental model in which eosinophils play a very prominent role.