Shared idiotopes between anti-class II monoclonal antibodies and major histocompatibility complex recognition site of T cells.

We have raised a number of monoclonal antibodies (mAb) against idiotopes (Id) on monoclonal anti-murine class II (anti-Ak or Ek) antibodies. Two anti-Id mAb among 31 were found to cross-react with some T cells but not with macrophages and B cells of H-2k animals. They were able to block syngeneic mixed lymphocyte reaction (SMLR) and antigen-induced major histocompatibility complex (MHC)-restricted T cell proliferation of H-2k but not of other haplotypes. These results indicated that antibodies were recognizing Id associated with the MHC restriction site of T cells. The injection of these anti-Id mAb into H-2k mice resulted in the stimulation of self-class II-reactive T cell clones as determined by SMLR. They were also able to stimulate in non-H-2k strains to prime H-2k alloreactive T cell clones. Some animals developed anti-class II (anti-Iak) antibodies by the injection of anti-Id. These results indicated that certain anti-Id (anti-anti-class II) antibodies cross-reacted with T cell receptors which carried class II restriction specificity and were involved in allorecognition. These antibodies were found to have an ability to alter the T cell repertoire in vivo by stimulating such MHC-restricted clones.