Xenobiotics may contribute to the pathogenesis of PBC by triggering autoimmune reactions. Different mechanisms for the induction of autoimmunity by xenobiotics have been proposed [86, 130] . A potential direct toxic effect of xenobiotics my cause cell death by apoptosis or oncosis, inducing the generation of immunogenic autoepitopes. In addition, chemical modification of native cellular proteins by removal and/or exchange of a hapten has been shown to change processing in antigen-presenting cells and may lead to the presentation of cryptic, potentially immunogenic peptides. Furthermore, xenobiotics may have the potential to modify host proteins to form neoantigens. Neoantigenspecific T cells and B cells, once primed, may cross-react with the formerly inert native autoantigens. In accordance with this hypothesis, Amano et al. [131] studied a number of xenobiotics with a structure similar to lipoic acid, a residue on the E2 epitope of the pyruvate dehydrogenase complex (PDC-E2), the main autoreactive antigen identified in PBC so far in PBC. Replacement of lipoic acid by certain xenobiotics enhanced the reactivity of PBC sera against the PDC-E2 epitope. Particularly, one of the xenobiotics, 2-nonynoic acid, induced reactivity of PBC sera stronger than that of the native lipoic acid residue. Interestingly, the methyl ester of 2-nonynoic acid has a viol-/peach-like scent and is used as an ingredient in perfumes. It is ranked 2,324th out of 12,945 chemical compounds in terms of occupational exposure with an 80% female preponderance due to its use in cosmetics.