IgA Anti-b2GPI Antibodies in Patients with Autoimmune Liver Diseases

Recently, we reported a high prevalence of immunoglobulin G and/or immunoglobulin M anticardiolipin antibodies (aCL) in patients with autoimmune liver diseases, namely, autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), and primary sclerosing cholangitis (PSC), which were independent of the respective isotypes of antibodies against β2-glycoprotein I (anti-b2GPI). Immunoglobulin A (IgA) aCL and IgA anti-b2GPI are the least studied of the three specific isotypes either in antiphospholipid syndrome (APS) or in other conditions. Therefore, we investigated the prevalence and clinical significance of IgA anti-b2GPI and IgA aCL by enzyme-linked immunosorbent assays in another set of Caucasian patients with autoimmune liver diseases (59 AIH, 96 PBC, and 37 PSC). The disease controls group consisted of 50 hepatitis C virus (HCV) patients, 50 hepatitis B virus (HBV), 30 alcoholic liver disease (ALD), 30 non-alcoholic steatohepatitis (NASH), and 110 healthy controls. IgA anti-b2GPI prevalence was higher in AIH (50.8%) compared to PBC (p = 0.005), PSC (p = 0.008), NASH (p = 0.004), ALD (p = 0.01), and HCV (p = 0.002). The titers were also significantly higher in AIH compared to any other group of the study. IgA aCL prevalence was higher in AIH (33.9%) compared to PBC (p = 0.005), PSC (p = 0.014), NASH (p = 0.001), ALD (p = 0.004), and HCV (p < 0.001). IgA anti-b2GPI or IgA aCL were not associated with APS features in patients with liver autoimmunity. Of note, IgA anti-b2GPI and IgA aCL were associated with clinical and biochemical markers of disease severity in AIH and PBC. We demonstrated a high prevalence and high titers of IgA anti-b2GPI in patients with AIH compared to any other liver disease of the study. IgA anti-b2GPI and IgA aCL were associated with the severity and biochemical activity of AIH and PBC, but long-term prospective studies are needed to address whether this new finding is of clinical importance in AIH and PBC patients.