The significance of antimitochondrial IgA and IgG in the diagnosis of primary biliary cirrhosis

Objective: To evaluate the sensitivity and the specificity of Anti-M2-3E ELISA for the detection of IgG- and IgA-specific isotypes of antimitochondrial antibody (AMA), and to investigate the significance of antimitochondrial IgA and IgG in the diagnosis of primary biliary cirrhosis (PBC).

Methods: Sera were collected from 107 PBC patients, 87 disease controls and 26 healthy controls, and the antimitochondrial antibodies (IgG and IgA) were detected using indirect immunofluorescence (IFL), Anti-PDC ELISA and Anti-M2-3E ELISA.

Results: The AMA IgG positive rate in PBC patients was 90.6% detected by Anti-M2-3E ELISA, which is significantly higher than that (81.3%) detected by IFL(t = 4.32, P < 0.05) and that (72.9%) detected by Anti- PDC ELISA (t = 6.03, P < 0.05). The AMA IgA was positive in 59 of the 107 PBC patients, and 99 of the 107 patients were positive for AMA IgG or/and IgA. 9 of the 20 IFL-negative patients were positive for AMA IgG as indicated by Anti-M2-3E ELISA, 11 of the 20 IFL-negative patients were positive for AMA IgG or/and IgA as indicated Anti-M2-3E ELISA. Compared to patients negative for IgG AMA, patients positive for IgG AMA had more severe histopathology and higher levels of ALP, IgG, and IgM.

Conclusions: The IgG and IgA Anti- M2-3E ELISAs are more sensitive for the AMA detection than IFN and the Anti-PDC ELISA. The presence of AMA IgG is the characteristics of severe PBC.