PBC is an autoimmune disease associated with an inflammatory response localized to the small bile duct cells of the liver Ludwig, 2000) . While attempts to establish an animal model for PBC in a number of animal species, including several strains of mice, have had with little success (Krams et al., 1989; Zeniya, 2000) , Jones et al. have proposed an animal model for PBC termed "experimental autoimmune cholangitis" in which SJL/J mice are immunized with purified bovine PDC-E2 (Jones et al., 2000) . Both the use of SJL/J mice and bovine PDC-E2 may have been important factors in establishing this proposed model of PBC. Unclear susceptibility factors in SJL/J mice have made these mice useful for the establishment of models of other autoimmune diseases (Vidal et al., 1994; Abedi-Valugerdi and Moller, 2000; Winer et al., 2001) . Additionally, purified bovine PDC-E2 may be more efficient at inducing an immune response for several reasons. In our hands, native PDC-E2 isolated from bovine heart tissue induces a stronger response than E. coli-produced recombinant protein when injected into mice (unpublished data). First, it has been suggested that lipoic acid is essential for optimal antigenicity (Fregeau et al., 1990; Bassendine et al., 1998; Koike et al., 1998) . Native protein is lipoated while synthetic peptides and recombinant proteins may not be lipoated. Second, it is important to note that bovine PDC-E2 differs from murine PDC-E2 by 28% at the amino acid level as determined by a protein blast. However, the antigenic region of bovine PDC-E2, including lipoic acid, has high homology with the murine protein and thus select regions may be recognized as a foreign antigen or altered self by the murine immune system. It thus may induce a stronger immune response against the autoantigen than a recombinant self protein or peptide (Coppel and Gershwin, 1995; Mackay, 2000) .