Serum immunoglobulin G subclasses in patients during acute hepatitis A.

IgG subclasses were measured in sera of 47 patients with acute hepatitis A during the course of the disease. IgG1 and IgG3 serum levels were found to be elevated, whereas IgG2 and IgG4 subclass concentrations did not differ from that found in healthy control individuals. These findings indicate that, similar to the specific antiviral antibody, the polyclonal increase of serum concentrations of IgG in acute hepatitis A is not equally distributed to all IgG subclasses but is restricted to IgG1 and IgG3.