Demonstration of a transient rheumatoid factor in the acute phase of hepatitis non A, non B

The evaluation of an enzyme-linked immunosorbent assay (ELISA) test designed to detect antigens of hepatitis non A, non B (HNANB) revealed that a rheumatoid factor (RF)-like reaction was interfering. This RF-like reaction was not detectable by routine screening methods for RF, such as latex agglutination or the Waaler Rose test. Testing of sequential sera of chimpanzees with acute HNANB showed that this RF-like reaction was present in the acute phase of HNANB simultaneously with alanine aminotransferase (ALT) elevations. Characterization of this RF-like reaction revealed the presence of an IgM antibody against human IgG that banded in CsCl at 1.3 g/ml and at 19S in sucrose gradients. Absorption with IgG-coated latex particles and anti-human IgM gave further evidence of an RF. By testing sera of patients with different forms of acute viral hepatitis, it was demonstrated that an RF-like factor was also present in seven sera from 9 patients with acute hepatitis A, in two sera from 11 patients with hepatitis B, and seven sera from 11 patients with acute HNANB. The rise of RF in the acute phase of hepatitis A may be an effect of polyclonal stimulation of IgM producing B lymphocytes. The high prevalence of RF in HNANB remains unclear as no polyclonal stimulation of IgM has been observed.