Immunofluorescent studies of thyroid auto-antibodies in chickens of the obese strain (OS).

Chickens of the Obese strain (OS) exhibit a hereditary, spontaneous auto-immune thyroiditis. Thyroglobulin auto-antibodies have so far been demonstrated by passive haemagglutination and precipitation. A standardized indirect immunofluorescent staining system has been established as an additional technique for the demonstration of these antibodies. Two kinds of circulating thyroglobulin antibodies were found in OS chickens, one demonstrable by passive haemagglutination only, the other by both precipitation and indirect immunofluorescence using a fluorescein isothiocyanate conjugate directed predominantly against chicken IgG. Results obtained in chessboard type indirect immunofluorescence blocking tests and with column chromatographic fractions of OS sera are suggestive that the haemagglutinating kind of thyroglobulin antibodies are of the IgM class, while the antibodies reactive in precipitation and indirect immunofluorescence are of IgG type. The autoantibody nature of the thyroglobulin antibodies in OS chickens was demonstrated by indirect and direct immunofluorescent staining of autologous thyroid sections. With the immunofluorescence techniques employed so far, antibodies directed against antigenic components of the thyroid epithelium of OS chickens have not been demonstrated.