Indirect immunofluorescence staining of human thyroid by antibodies occurring in Yersinia enterocolitica infections.

In the diagnostic routine for tissue antibodies, using indirect immunofluorescence on cryostat sections of human thyrotoxic thyroid, rat stomach and kidney, ninety-six out of 48,388 sera showed a marginal staining of the membrane region of thyroid epithelial cells but no other reaction. Twenty-six of these sera were from patients with acute Yersinia enterocolitica serotype 3 infection but without signs of thyroid disease. Fifty of sixty-three sera with agglutinins against Y. enterocolitica serotype 3 and three out of four sera with agglutinins against Y. enterocolitica serotype 9 also showed this reaction on thyroid sections. It was due to antibodies, mostly of the IgG class, occurring in low titre, which react with intracytoplasmic antigens in thyroid, as staining of live thyroid epithelial cells was negative. The pattern of immunofluorescence on thyroid sections caused by these antibodies could not be distinguished from that caused by smooth muscle antibodies by appearance only. However, smooth muscle antibodies react also on other tissue sections and extracts of contractile proteins which absorb out these, did not change the reaction on thyroid of Y. enterocolitica sera. Absorption with sonicated Y. enterocolitica 3 and 9 antigens, but not with heat-killed whole bacteria, extinguished the reaction on thyroid. This indicates the presence of a cross-reactivity between antigens in these bacteria, different from the O antigen, and antigens in thyroid epithelial cells. Knowledge of this pattern of immunofluorescence on thyroid sections can be of diagnostic significance.