Identity of antibody to hepatitis B e/1 antigen as an atypical rheumatoid factor.

Chronic carriers of hepatitis B surface antigen (HBsAg) who were positive for antibody to hepatitis B e antigen were tested for precipitating specificities of the antibody and for rheumatoid factor (RF) over a two-year period. Twenty-one of 69 carriers were RF-positive by the latex-RF test with human IgG, but all were negative by the hemagglutination-RF test with rabbit IgG. Antibody to e/1 antigen was identified as an IgM antibody reactive in the latex-RF test, whereas antibody to e/2 antigen belonged to the IgG class and showed no RF reactivity. Antibody production seems to follow a sequential evolution: antibody to e/1 antigen appears early and that to e/2 antigen follows shortly thereafter. Antibody to e/2 antigen remains as the permanent antibody, whereas that to e/1 antigen sometimes disappears. The fact that antibody to e/1antigen is present only in certain chronic carriers of HBsAg would account for discrepancies in reported results of RF test in viral hepatitis.