Parabiosis between obese (OS) and normal strain chicken embryos. Examination of skin grafts, lymphocyte chimerism and autoimmune thyroiditis.

Embryos of the Obese strain (OS) of chickens, a strain with spontaneously occurring autoimmune thyroiditis, were parabiosed with embryos derived from two normal strains by chorioallantoic membrane anastomosis. The chicks, which hatched shortly after these membranes dried, developed separately. They were examined for the presence of thyroiditis and for the effectiveness of the parabiosis procedure in transferring blood-borne factors. It was observed that the parabiosis procedure was at least partially effective in that it resulted in prolonged skin graft survival in most instances, and in the development of lymphoid cell chimerism in four of fourteen chickens, still detectable 7 weeks after hatching. Parabiosis failed to have any significant effect on the development of thyroiditis in the OS or on the normal strains in three separate experiments; the OS chicks developed severe thyroiditis and the normal chicks remained normal. This suggests a lack of pathogenic agents in the bloodstream of OS embryos.