in vitro immune responses to hepatitis b surface antigen pres2 and s following remote infection by hepatitis b virus in humans in this report we evaluate the human immune response to hepatitis b surface antigen hbsag following remote infection with hepatitis b virus hbv hbsagreactive lymphocytes can be readily demonstrated in the peripheral blood of individuals with established immunity following infection with hbv in vitro stimulation with small doses of plasmaderived hbsag yeastderived hbsag s region or pres2 peptide will induce specific igg to hbsag antihbs in the absence of a polyclonal increase in total igg the pres2 peptide will stimulate in a t celldependent fashion the in vitro production of antihbs with specificity for the s domain this antihbs production is mediated by pres2stimulated soluble tcell factors peripheral blood mononuclear cells from individuals with established immunity proliferate to the yeastderived hbsag but not to the plasmaderived hbsag or pres2 peptide the chronic hbsag carriers do not produce antihbs following stimulation with hbsag regardless of the source or component of antigen used different study protocols failed to demonstrate hbsagspecific responses in the peripheral blood mononuclear cells of chronic carriers