Target organ defects in thyroid autoimmune disease

Hypothesis. Bystanders or bad seeds? Many autoimmune-target cells may be transforming to cancer and signalling "danger" to the immune system

Autoimmune-target cells in autoimmune disease (AID) are usually construed as constitutionally normal healthy cells. A related assumption is that other cells in the body of AID patients, except for certain immunocytes, are healthy cells. An implication of that view is that any systemic pathology in organ-specific AID is related to metabolic derangements secondary to tissue destruction. However, much data on target and other cells in AID suggest widespread primary cellular defects. In insulin-dependent diabetes mellitus (IDDM), for example, many "complications" such as atherosclerosis, premature arterial stiffening, senescence of fibroblasts in vitro, and exuberant growth of smooth muscle and mesangial cells in vivo are not strictly attributable to glucose elevation. Also unexplained is the similar appearance of IDDM beta-cells and cells from insulinoma and why the prodromal phase of IDDM has many insulinoma-like features. While AID target cells have often been likened to neoplastic cells, investigators have rarely explored the possibility that autoimmunity in AID is fundamentally antineoplastic. This is likely because the dominant ideas in oncology and immunology-somatic mutation and clonal deletion, respectively-have prevented explanations for how normal immunity could detect transforming cells not expressing non-self antigens. New and less conventional theories of cancer and immunity have facilitated such an explanation. I use Rubin's "epigenetic" aging model of carcinogenesis and Matzinger's "danger" model of immunity to integrate the immunological and oncological sides of AID. In particular, I postulate that individuals suffering from AID have inherited many foci of prematurely aging cells. Those inherently damaged cells adapt to in vivo challenges by beginning to transform into cancer cells. However, as long as those stressed cells have not fully transformed, they will continue to signal "danger" to the innate immune system. The clinical outcome of that struggle between incipient neoplasia and immunity will vary depending upon the degree of tumor-proneness and resistance of the individual. Borrowing from cancer geneticist Henry Lynch, I postulate that tumor-resistance is inherited as a quantitative polygenic trait in direct proportion to tumor-proneness. I further contend that tumor-proneness and immunity are linked polygenic traits such that the greater one's tumor-proneness, the more powerful his/her antitumor immunity. I point to the shared DNA repair deficiency of certain cancer-prone syndromes and HLA-linked AID, their occasional co-occurrence, and their demonstrably exceptional immunity against solid tumors. I propose that HLA-linked AID constitute "chronic hypersensitivity syndromes" due to immunity's largely hidden battle to suppress multiple incipient neoplastic microfoci. Much of the physiopathology of AID is explicable as a sustained systemic response to threatened neoplastic transformation.

Expression of nonspecific esterase (NSE) by thyroid follicular epithelium as a marker for the target organ susceptibility to immune system attack

Spontaneous autoimmune thyroiditis in obese strain (OS) chickens provides an excellent animal model for the study of Hashimoto's autoimmune thyroiditis in humans. The data presented in this paper indicate that nonspecific esterases (NSE) may play a role in or serve as a marker for the target organ susceptibility. Experiments have shown that follicular epithelial cells and interfollicular macrophages in connective tissue stain positively for NSE as early as the first day after hatching, a time at which infiltrating lymphocytes are not yet observed. We also have observed NSE positivity of follicular cells in the vicinity of mononuclear cell infiltration in all OS chickens, as well as weaker positivity in 6-month-old, avian leukosis virus free, Brown Leghorn outbred chickens, which appears in each case to correlate with infiltration of lymphocytes. In F2 hybrids between OS and healthy CB inbred chickens, the intensity of NSE staining was more variable than in OS chickens. Using specific inhibitors eserine, Na-taurocholat and p-hydroxymercuribenzoic acid, we were able to inhibit in vitro the NSE positivity of thyroid gland follicular epithelium, indicating that this staining was not an artifact. Experiments are currently in progress to clarify the relationship between the presence of NSE in follicular epithelium and the predisposition to spontaneous autoimmune thyroiditis.

Target organ susceptibility and autoantibody production in an animal model of spontaneous autoimmune thyroiditis

F1-hybrids of Obese strain (OS) chickens, afflicted with spontaneous autoimmune thyroiditis (SAT), and normal, inbred CB chickens, do not develop severe thyroiditis. About 50% of these crosses show circulating autoantibodies to thyroglobulin (TgAAb), but the thyroid glands are only slightly infiltrated, suggesting that the target organ is not susceptible to autoimmune attack. In the present study we show that despite this mild infiltration TgAAb are only synthesized by lymphoid cells within the thyroid gland. Furthermore, we demonstrate that immunization with chicken thyroglobulin (Tg) in complete Freund's adjuvant causes severe experimental autoimmune thyroiditis (EAT) in F1(OSxCB) hybrids.

Molecular analysis of genetically determined target organ abnormalities in spontaneous autoimmune thyroiditis

We have shown in earlier studies, that the development of spontaneous autoimmune thyroiditis (SAT) in chickens of the Obese strain (OS) depends on the presence of both, two dominant genes coding for an altered immune regulation and one recessive gene responsible for the susceptibility of the target organ for the autoimmune attack. The product(s) of the latter is (are) still not known. The present study was aimed at identifying possible candidates of cellular components of the thyroid gland of OS chicken and its SAT susceptible parental Cornell C-strain (CS) by high resolution 2-dimensional (2D) gel electrophoresis. For this purpose organ cultures of the thyroid, bursa, thymus and liver were established and the synthesized polypeptides were labelled by 35S-methionine. OS and CS organs were compared with those of healthy normal White Leghorn (NWL) controls. The autoradiographs of the 2D-gels obtained from individual samples after various labelling periods were subjected to comparative analysis. We have found both quantitative and qualitative differences of polypeptide spots between OS/CS and NWL organ samples, some of them specific for the thyroid gland. Although one has to be aware that in this multidimensional analytical approach numerous, still elusive pattern differences are revealed, the thyroid specific phenomena will be further scrutinized.