Appearance of immune complexes during experimental hepatitis A infection in chimpanzees.

Circulating immune complexes (CICs) were detected during the course of experimental hepatitis A virus (HAV) infection in 8 of 9 chimpanzees. In all cases, the predominant class of antibody detected in the CIC was IgM. The appearance of IgM-CIC usually preceded the onset of liver enzyme elevations, and in all instances, the appearance of IgM-CIC correlated with the presence of IgM anti-HAV. Six of 8 animals tested had significant depression of C3 concentrations during the course of infection, and this depression occurred at the peak of CIC activity. Immunohistologic studies demonstrated granular deposits of IgM localized in sinusoidal cells during peak of IgM-CIC activity. IgM-CICs appear to be a fairly consistent finding during HAV infection and probably represent the viremic phase of the disease. However, they do not appear to mediate hepatocellular injury by direct action on hepatocytes.