Clinical significance of low molecular weight (7-8S) immunoglobulin M antibody to hepatitis B core antigen in chronic hepatitis B virus infections.

Separation of 7-8S and 19S forms of serum immunoglobulin M (IgM) hepatitis B core antibody (anti-HBc) by rate-zonal centrifugation was carried out on serum from 80 American chronic carriers of hepatitis B surface antigen (HBsAg), all of whom were positive for IgM anti-HBc and had elevated levels of serum alanine aminotransferase (mean 164 IU/L). Seventy-three of the 80 sera showed a predominance of one or the other form of IgM anti-HBc. Fifty-four (68%) had predominantly 7-8S IgM anti-HBc, and 19 (24%) had predominantly 19S IgM anti-HBc. Sex, age, length of HBsAg-carrier state, mean alanine aminotransferase, mean total IgM anti-HBc level, presence of hepatitis B e antigen, and liver histology were similar in both groups. 19S IgM anti-HBc was detected in 11 (41%) of 27 male homosexuals compared with only 8 (17%) of 46 heterosexual patients (p = 0.03). Despite this apparent association, an explanation for the variable presence of 19S and 7-8S IgM anti-HBc predominance in chronic hepatitis B remains lacking.