Two monoclonal antibodies (MAbs) against interphotoreceptor retinoid-binding protein (IRBP) were previously established. One of the antibodies designated as MAb-TRA4 reacted with the IRBP of multiple species. Using this MAb-TRA4, 6 clonal anti-idiotypic monoclonal antibodies (MAb-TRDy; y = 1-6) against MAb-TRA4 were established. All of the MAb-TRDy were characterized by ELISA, immunoblotting and immunohistochemical studies. It was shown by ELISA that MAb-TRDy inhibited the specific binding between IRBP and MAb-TRA4 and did not cause nonspecific binding to rat polyclonal immunoglobulins (IgG and IgM). Immunoblotting assay demonstrated that MAb-TRDy inhibited the binding between IRBP and MAb-TRA4. Immunohistochemical examination also confirmed the immunological characterization of MAb-TRDy. Thus the present results indicate that the MAb-TRDy which have been established are the anti-idiotypic MAbs against anti-IRBP MAb-TRA4. MAb-TRDy can be used as a tool to study the pathogenesis of experimental autoimmune uveitis induced by IRBP.