Bacterial virulence antigens and the pathogenesis of autoimmune thyroid diseases (AITD).

There is now substantial evidence that autoimmune thyroid diseases (AITD) coincide with a subclinical persisting infection with Yersinia enterocolitica (YE) which manifests through humoral and cellular immune reactions against YE at the onset of AITD. The humoral and cellular crossreactivities of YE with thyroid autoantigens are exclusively directed against conformational epitopes of YE membrane associated antigens and of YE plasmid encoded virulence proteins (YOPs). Especially, the outer membrane domain of the TSH-Receptor (THSR) appears to have conformational homologies with YE antigens. Immunological- and molecular findings, however, do not allow definite conclusions about a potential role of YE-infection in AITD, although the evidence is suggestive. Recent investigations on the effect of YE-superantigen (Sag) on T-cells from patients with AITD as well as AITD like manifestations in YE immunized mice and rats may yield more conclusive information about the role of YE infection in the pathogenesis of AITD.