Analysis of the initiation period of spontaneous autoimmune thyroiditis (SAT) in obese strain (OS) of chickens.

The early, predictable, onset of spontaneous autoimmune thyroiditis (SAT) in Obese strain (OS) chickens provides a unique opportunity to analyse the mechanisms initiating autoimmunity which is virtually impossible to obtain in humans. In this study we focused on the respective roles of viruses and macrophages in the initiation of SAT. To analyse viruses, leukosis virus-free OS chickens were bred over three generations and reared under gnotobiotic conditions. By 2 weeks of age there were no differences in the levels of thyroid mononuclear cell infiltration between these and control animals. The role of mononuclear phagocytes in SAT was determined by their depletion via injecting newborn OS chicks with silica or carrageenan and dichloro-methylene diphosphonate encapsulated into liposomes. Although this treatment did not substantially change the amount of macrophages in primary lymphoid organs or blood, there was destruction of splenic architecture and, most importantly, mononuclear cell infiltration of the thyroids was significantly lower compared to controls. The role of activated macrophages in SAT is discussed.