IgM‐Induced Specific Antibody Responses: Direct Correlation between Responsiveness and Natural or Induced Recurrence of the Idiotype

The idiotype (Id) expressed on antibodies of the trinitrophenol (TNP)‐spccific BALB/c hybridoma TNP.11 is defined as a ‘nonrecurrent’ or private Id in BALB/c mice, whereas the analysis of splenic plaque‐forming cells (PFC) and circulating antibody in DBA/2 mice immunized with TNP antigens revealed that TNP.11 is a ‘recurrent’ Id in this strain. TNP.11 antibodies were characterized by their ability to induce an antigen‐independent anti‐TNP response in these two strains. Whereas this antibody was negative in BALB/c mice [18], a clearcut increase in splenic anti‐TNP PFC, preferentially expressing the TNP.11 Id, was observed in DBA/2 mice. This correlation between Id recurrency and ability to induce antigen‐independent responses was further probed in BALB/c mice repeatedly immunized with anti‐TNP.11 Id antibodies (Ab3). Such BALB/c mice express the TNP.11 Id in detactable amounts even without antigen challenge and respond with increased numbers of splenic anti‐TNP PFC to the injection of low amounts of TNP.11 antibody. These findings suggest that the ability of an antibody to induce antigen‐independent PFC responses is associated with the‘recurrency’, either natural or induced, of the antibody Id.