Specific antigedantibody complexes induce the in vivo production of a parallel set of nonantigen‐binding idiotype‐positive antibodies

摘要

AbstractImmune complexes prepared with the polysaccharide antigen (PnC) extracted fromStreptococcus pneumoniaeR36a and two different PnC‐specific antibodies were found to differ in their regulatory properties depending on the isotype of the antibody. Thus, complexes formed in antibody excess with TEPC15 (IgA) were suppressive whereas complexes formed with 96‐G (IgG3) antibodies enhanced the IgM response to PnC. During the course of these studies, we found that little or no PnC‐specific IgG antibody was induced during the response to PnC coupled to sheep red blood cells (PnC‐SRBC). Interestingly, however, immunization with 96‐G/PnC complexes either alone or with PnC‐SRBC resulted in the induction of IgG3antibodies that express the TI5 idiotype (Id) but which do not bind PnC. This unique IgG3response occurred after injection of 96‐G/PnC complexes formed in antibody excess but not when complexes were formed in antigen excess. The Id+nonspecific IgG3response peaked on day 5 and could be activated with 96‐G/PnC complexes but not with free PnC antigen. The Id+nonspecific response was not due to polyclonal activation of IgG3production since there was no difference in IgG3levels in mice injected with 96‐G/PnC complexes with those injected with PnC‐SRBC. Finally, mice that had been suppressed for expression of the T15 Id by neonatal injection of anti‐Id antibody were able to produce Id+‐unspecific IgG3antibody after immunization with 96‐G/PnC complexes, further suggesting that Id+IgG3was produced by different clones than those that usually comprise the antibody response to PnC. The results suggest that the formation of IgG immune complexes during an immune response may result in stimulation of idiotypically related clones thus resulting in degenera