Hepatitis B virus (HBV)‐specific in vitro antibody production by peripheral blood mononuclear cells (PBMC) after vaccination by recombinant hepatitis B surface antigen (rHBsAg)

To study the immunization induced by rHBsAg, we analysed the in vitro antibody production (IVAP) to HBsAg by PBMC from 18 subjects vaccinated by two injections on days 0 and 30. HBsAg‐specific IVAP was detectable in all subjects after both the first and the second injection, and lasted for about 10 days and then disappeared. However, when the spontaneous HBsAg‐specific IVAP became negative, HBsAg stimulation of PBMC cultures induced again a specific HBsAg IVAP. Cultures of cell populations separated by erythrocyte rosetting or Percoll density centrifugation showed that the cells responsible for spontaneous secretion, after in vivo stimulation, were low‐density B lymphocytes. High‐density B lymphocytes were involved in anti‐HBs production induced by in vitro stimulation when spontaneous secretion disappeared. These data suggest that the IVAP test could be a source of important information along with serologic analysis for exploration of the immune response to hepatitis B vaccine.