Demonstration of a Saturable Binding Site for Thyrotropin in Yersinia enterocolitica

Several lines of evidence suggest that there might be immunologic crossreactivity between the thyroid plasma membrane in humans and antigenic determinants in the enteric pathogen Yersinia enterocolitica. Studies were therefore performed to determine whether Y. enterocolitica, like the thyroid membrane, contains a thyrotropin binding site. A saturable binding site for bovine thyrotropin was indeed demonstrable, particularly in preparations of the organism that have been treated with ethylenediaminetetraacetate and lysozyme. Hormonal specificity of the binding site, as judged from the inhibition of binding of $^{125}$I-labeled bovine thyrotropin, was similar to that of the thyrotropin receptor in human thyroid tissue.