Clinical significance of immunoglobulin A antibody to hepatitis B core antigen of polymeric and monomeric forms in chronic type B liver disease with acute exacerbation.

Serum immunoglobulin A (IgA) hepatitis B core antibody (anti-HBc) was measured by a solid-phase enzyme immunoassay using monoclonal antibodies in sera from chronic carriers of hepatitis B surface antigen (HBsAg). To reinforce the clinical significance of IgA anti-HBc, levels of IgA subclasses and molecular characterization of IgA anti-HBc in sera of 13 patients in the acute exacerbation phase and the remission phase were compared. IgA anti-HBc was significantly higher in sera in the acute exacerbation phase than in the remission phase (p less than 0.025); in particular, more significant changes were observed in IgA2 anti-HBc (p less than 0.0025) and in secretory IgA anti-HBc (p less than 0.001). Analysis of molecular size distribution of IgA anti-HBc by high performance liquid chromatography showed that the elevation of polymeric IgA anti-HBc was significantly greater than that of monomeric IgA anti-HBc in the acute exacerbation phase (p less than 0.05), although there was an increase in both monomeric and polymeric IgA anti-HBc. Thus, the elevation of polymeric IgA anti-HBc suggests that the focal immune response against HBcAg in the liver and secretory IgA anti-HBc is an important marker of acute exacerbation in patients with HBsAg-positive chronic liver disease.