[en] C57BL/10 spleen cells were incubated for 18 hrs with monoclonal GAT-TsF1 and soluble GAT, and fused with BW5147. Hybridomas that did not produce GAT-TsF2 constitutively but could be induced by GAT-TsF1 to do so were cloned. One such clone (1556A2.1) was shown to bind GAT via a cell surface structure having the properties of a classical receptor. Binding of ¹²⁵I-GAT was saturable and maximal by 4 hrs at 4⁰C. Scatchard analysis indicated 5.8 x 10⁴ binding sites per cell with an avidity of 8 x 10^-14M. Binding of ¹²⁵I-GAT was specific because cold GAT, GT, and GLT competed for binding, whereas BSA and GA did not. Furthermore, monoclonal antibody against a shared anti-GAT idiotype also blocked binding of ¹²⁵I-GAT. Finally, the antigen-binding receptor isolated from uninduced 1556A2.1 hybridoma failed to complement independently isolated I-J⁺ chain from TsF2 obtained from induced 1556A2.1. These data suggest the presence of a molecule on the Ts₂ cell capable of binding antigen which is related to, but functionally different from, the TsF2 antigen-binding chain