Cell-mediated immunity of Yersinia enterocolitica serotype 3 in patients with thyroid diseases

Environmental Basis of Autoimmunity

The three common themes that underlie the induction and perpetuation of autoimmunity are genetic predisposition, environmental factors, and immune regulation. Environmental factors have gained much attention for their role in triggering autoimmunity, with increasing evidence of their influence as demonstrated by epidemiological studies, laboratory research, and animal studies. Environmental factors known to trigger and perpetuate autoimmunity include infections, gut microbiota, as well as physical and environmental agents. To address these issues, we will review major potential mechanisms that underlie autoimmunity including molecular mimicry, epitope spreading, bystander activation, polyclonal activation of B and T cells, infections, and autoinflammatory activation of innate immunity. The association of the gut microbiota on autoimmunity will be particularly highlighted by their interaction with pharmaceutical agents that may lead to organ-specific autoimmunity. Nonetheless, and we will emphasize this point, the precise mechanism of environmental influence on disease pathogenesis remains elusive.

A Potential Link between Environmental Triggers and Autoimmunity

Autoimmune diseases have registered an alarming rise worldwide in recent years. Accumulated evidence indicates that the immune system's ability to distinguish self from nonself is negatively impacted by genetic factors and environmental triggers. Genetics is certainly a factor, but since it normally takes a very long time for the human genetic pattern to change enough to register on a worldwide scale, increasingly the attention of studies has been focused on the environmental factors of a rapidly changing and evolving civilization. New technology, new industries, new inventions, new chemicals and drugs, and new foods and diets are constantly and rapidly being introduced in this fast-paced ever-changing world. Toxicants, infections, epitope spreading, dysfunctions of immune homeostasis, and dietary components can all have an impact on the body's delicate immune recognition system. Although the precise etiology and pathogenesis of many autoimmune diseases are still unknown, it would appear from the collated studies that there are common mechanisms in the immunopathogenesis of multiple autoimmune reactivities. Of particular interest is the citrullination of host proteins and their conversion to autoantigens by the aforementioned environmental triggers. The identification of these specific triggers of autoimmune reactivity is essential then for the development of new therapies for autoimmune diseases.

Immunoglobulins of patients recovering from Yersinia enterocolitica infections exhibit Graves' disease-like activity in human thyroid membranes

Substantial evidence suggests a link between infections with Yersinia enterocolitica (YE) and Graves' disease. We have now examined the sera of 72 patients recovering from YE infection for immunoglobulins that interacted with the TSH receptor in human thyroid membranes. Compared with controls, in concentrations between 1 and 4 mg/mL, patient IgG produced a significant, concentration-dependent inhibition of TSH binding (p less than 0.001) and stimulation of adenylate cyclase activity (p less than 0.005-0.05). Whereas IgG from normal individuals caused no stimulation of adenylate cyclase, IgG from controls caused some concentration-dependent displacement of TSH, as previously reported. However, IgG from convalescents of YE infections was significantly more potent than normal IgG in reducing the binding of TSH to the membrane. Thus, at each examined concentration, YE patients' IgG displaced more TSH than IgG from normal controls. For each milligram per milliliter increment of IgG in the assay, patients' IgG caused a 10.2% inhibition of TSH binding (r -0.90, p less than 0.001), significantly greater than that seen with normal IgG (p less than 0.02). The present studies provide the first demonstration that IgG of patients recovering from YE infections react with the human TSH receptor. The antibodies presumably are produced against the TSH-binding protein present in YE. However, in view of lack of evidence for thyroid dysfunction in the sera of patients recovering from yersiniosis and the presence of TSH-binding proteins in other bacteria, we postulate that infection with YE is neither necessary nor sufficient to cause thyroid autoimmune disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Yersinia enterocolitica and thyroid autoimmunity

The concordance rate of Graves' disease in pairs of identical twins of 30 to 60% points to the influence of environmental factors, and infections have often been incriminated in the pathogenesis. More than 15 years ago we demonstrated an increased frequency of antibodies to Yersinia enterocolitica (Y. ent.) serotype 3, which later was confirmed by others, suggesting a link between infection with Y. ent. and autoimmune thyroid diseases.

Graves' disease and HLA: clinical and epidemiologic associations

Correlation between clinical and epidemiological features of Graves' disease and HLA were sought in 175 patients, eighty-three of whom were typed for HLA DR antigens. The relative risks (x) conferred by HLA-B8 and DR3 were 3.1 and 5.7 respectively (P less than 0.0005 uncorrected). The disease occurred at an earlier age in HLA-DR3 positive patients compared to negative patients (P less than 0.005 in females greater than and less than 30-years-old). Eighty-four out of ninety-two patients could specify the season of onset of hyperthyroidism; an excess of HLA-B8 positive patients in the summer and a lack of these in the spring and autumn was found. No association between B8 and exophthalmos and/or soft tissue eye changes were observed. However, significant associations between exophthalmos and either exophthalmos and/or soft tissue changes were found with DR3 (x = 3.6 and 3.8 respectively). HLA-DR3 positive patients were found to be more resistant to radioiodine therapy than patients negative for these antigens. No heterogeneity in the distribution of HLA antigens was found when the following indices were examined: sex, goitre size, severity of disease, pretibial myxoedema, antecedent psychological disorder, consumption of oral contraceptives, family history of Graves' disease or thyroid antibody titre. HLA does not appear to distinguish subvariants of Graves' disease, rather it influences the susceptibility to disease and its persistence once it becomes clinically manifest.