Induction of thyroiditis in guinea-pigs by intravenous injection of rabbit anti-guinea-pig thyroglobulin serum. II. Studies with fluorescent antibody technique.

The localization of rabbit γ-globulin was traced in the thyroids of guinea-pigs receiving rabbit anti-guinea-pig thyroglobulin serum intravenously. The fluorescent antibody technique was used. Rabbit γ-globulin was found in the interstitium and pericapsular region ¼ hour after the injection, and could be seen there for 24 hours. Five, 10 and 20 days after injection the interstitium was free of specific green-fluorescence. The first sign of specific fluorescence, associated with the epithelial cells, was seen as rounded droplets of fluorescent material after 1 hour. Thereafter, these droplets could be found, increasing in size, at all time intervals later studied. Twenty-four hours after injection green-fluorescent material was seen in some of the follicular lumina. However, most of these did not display any specific fluorescence. Granulocytes showing specific fluorescence were first observed 1 hour after injection, but this phenomenon was most evident at 12 and 24 hours. Both eosinophil and neutrophil granulocytes were found in the infiltrates, but it could not be decided whether both of these cell types were involved in the uptake of rabbit γ-globulin. The findings were discussed in relation to the previous reported observation of strongly PAS-positive material in the granulocytes. Together the observations suggested the uptake of both antigen and antibody, most probably as an antigen—antibody complex. The relevance of the observations in relation to thyroid physiology, as well as to experimental thyroiditis after active immunization and to chronic nonspecific human thyroiditis is discussed.