Involvement of epitope mimicry in potentiation but not initiation of autoimmune disease

We have examined whether the peptide (368-381) from the murine adenovirus t ype 1 E1B sequence, exhibiting a high degree of homology with the known pat hogenic thyroglobulin (Tg) T cell epitope (2695-2706), can induce experimen tal autoimmune thyroiditis (EAT) in SJL/J mice. The viral peptide was a poo r immunogen at the T or B cell level and did not elicit EAT either directly or by adoptive transfer assays. Surprisingly, however, the viral peptide w as highly antigenic in vitro, activating a Tg(2695-2706)-specific T cell cl one and reacting with serum IgG from mice primed with the Tg homologue, The viral peptide also induced strong recall responses in Tg(2695-2706)-primed lymph node cells, and subsequent adoptive transfer of these cells into nai ve mice led to development of highly significant EAT. These data demonstrat e that nonimmunogenic viral peptides can act as agonists for preactivated a utoreactive T cells and suggest that epitope mimicry may at times play a po tentiating rather than a precipitating role in the pathogenesis of autoimmu ne disease.