OBJECTIVEThe aim of this study was to evaluate the association between Chlamydia pneumoniae (CP) infection and primary biliary cirrhosis (PBC).

METHODSChlamydia pneumoniae IgG and IgM were determined by enzyme-linked immunosorbent assay (ELISA) in 41 well-established PBC patients and two race-matched control groups, PHC, n = 70; healthy controls, HC, n =57).

RESULTSThe mean levels and seroprevalence of CP IgG in PBC group and PHC group were significantly higher than in the HC [(46.8 +/- 43.4) RU/ml, (49.5 +/- 45.2) RU/ml vs (28.3 +/- 32.7) RU/ml, P = 0.042 and P < 0.001 respectively; 68.3%, 71.4% vs 42.1%, chi2 values were 5.389 and 11.110 respectively]. There was a markedly elevated seroprevalence of CP IgM in patients with PBC (22.0%) compared with the PHC and HC groups. The odds ratios (ORs) for the presence of CP IgG and IgM for the PBC patients versus the HC were 2.7 (95% CI 0.9 to 6.1) and 5.1 (95% CI 1.4 to 18.5). Though there was no correlation in the level of CP IgG with total IgG in sera of patients with PBC (r=-0.857, p=0.344), CP IgM was related with the abnormally high concentrations of total IgM in the PBC group.

CONCLUSIONSThe results of this study do not support the hypothesis that infection with Chlamydia pneumoniae may be a triggering agent for PBC, but suggest that Chlamydia pneumoniae infection probably contributes to the high level of IgM presented in most of the patients with PBC