The association of positive serological AMA in PBC patients with recurrent UTIs suggest a bacteria aetiology in PBC [7]. The hypothesis buy Deforolimus that E. coli is a cause of PBC was first proposed in 1984, based on the higher prevalence of this bacterium in women in PBC when compared with age-matched women with other chronic liver diseases [13]. More recently, Varyani et al. reported that recurrent UTIs are present within 1 year prior to the diagnosis of in 29% of patients in PBC compared to 17% of non-PBC chronic liver disease controls [14]. This hypothesis is also supported by the

demonstration of T and B cell cross-reactivity between AMA epitopes and E. coli PDC-E2 sequences [24, 27, 41]. The induction of autoimmune

diseases is considered to Cytoskeletal Signaling inhibitor be the result of complex interactions between genetic traits and environmental factors, including microbial infections [42]. The microbial aetiology of PBC is poorly defined and the pathogenic mechanisms of biliary injury in PBC remain largely unknown. Clues indicating a microbial aetiological component to the pathogenesis of PBC were based largely on experimental evidence of B and T cell cross-reactivity between the major mitochondrial autoantigens and their mimicking microbial antigenic epitopes [27, 29, 43-50]. Additional support comes from epidemiological studies, case reports or molecular evidence of the presence of microbial or viral agents in the liver or bile specimens of patients with PBC [13, 29, 50-52]. Several hypothetical mechanisms, such as bystander activation of autoreactive cells, induction of proinflammatory cytokines by microbial antigens and molecular mimicry between the microorganism and the host have been proposed to explain how microbes initiate autoimmunity [9-12]. Among these hypotheses, the theory of molecular mimicry has been addressed rigorously Flucloronide in PBC, which is based on the shared linear amino acid sequences or a conformational fit (for B cell cross-reactivity), or a motif (for T cell cross-reactivity) between a bacterial antigen and human ‘self’-antigen

[2, 28, 44, 53, 54]. An immune response directed against the mimicking microbial determinants may cross-react with the self-protein(s), and such autoreactivity may cause injury in targeted cells leading to cell destruction and, ultimately, autoimmune disease. In line with the theory of molecular mimicry, previously reported AMA cross-reactivity between the human PDC-E2 and its microbial counterparts in E. coli, N. aro and Lactobacillus delbrueckii suggested that PBC could be induced by exposure to these bacterial antigens [28, 42, 44, 55]. In addition, the identification of the 16S rRNA gene in livers from patients with PBC suggests that Propionibacterium acnes could be involved in granuloma formation in PBC [56].