Immunoglobulins of Patients Recovering fromYersinia enterocoliticaInfections Exhibit Graves' Disease-like Activity in Human Thyroid Membranes

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Abstract
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 < 0.001) and stimulation of adenylate cyclase activity (p < 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 membranes. Thus, at each examined concentration, YE patients' IgG displaced more TSH than IgG from normal controls. For each milligram per milliter increment of IgG in the assay, patients' IgG caused a 10.2% inhibition of TSH binding (r -0.90, p < 0.001), significantly greater than that seen with normal IgG (p < 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. Instead, we propose that YE, as well as infections by other bacteria containing TSH receptorlike proteins, may aim an autoimmune process to the thyroid gland in individuals otherwise predisposed to autoimmune disease.