Cytogenetic and immunologic studies in chickens with autoimmune thyroiditis.

IT has been suggested that thyroid autoimmunity might predispose to aberrations involving chromosome number 21 in humans-. This hypothesis has been supported by data from a number of studies--of the families of patients with trisomy 21 (Down's syndrome). These studies have revealed an increased prevalence of autoantibodies to thyroglobulin in patients with trisomy 21 and their mothers, compared to controls. Thyroid function and therapy in seropositive individuals is variable from case to case. Seropositive mothers are often less than 35 years old at the time of birth of the propositus, and translocations and mosaicism are represented in unusually large numbers among the propositi in these families. These findings are consistent with Penrose's age-independent mongolism, which may in some cases involve parental predisposition to meiotic or mitotic error. The relation between thyroid autoimmunity and trisomy 21 can be interpreted in a number of ways. First, thyroid autoimmunity might be the result of a chromosomal abnormality. This is unlikely, however, since seropositive mothers of trisomy 21 patients are usually chromosomally normal. Second, genetic factors for thyroid autoimmunity might be closely linked with possible factors leading to chromosomal abnormalities. A third possibility is that a condition related to the autoimmune process, such as viral infection or endocrinologic imbalance, might induce aberrations in chromosomes. Fourth, thyroid autoantibodies themselves may act to damage chromosomes. Fialkow has demonstrated chromosome damage in cultures of human fibroblasts exposed to extracts from allogeneic human lymphocytes. While this supports the fourth interpretation above, convincing demonstration that a factor can produce chromosomal abnormalities in vivo requires a carefully controlled, prospective study. Results of investigations in chickens with hereditary autoimmune thyroiditis are described in the present paper. Obese strain (OS)White Leghorn chickens