Structure of a γδ T cell receptor in complex with the nonclassical MHC T22

gamma delta T cell receptors (TCRs), alpha beta TCRs, and antibodies are the three lineages of somatically recombined antigen receptors. The structural basis for ligand recognition is well. defined for alpha beta TCR and antibodies but is lacking for gamma delta TCRs. We present the 3.4 angstrom structure of the murine gamma delta TCR G8 bound to its major histocompatibillity complex (MHC) class Ib ligand, T22. G8 predominantly uses germ line-en coded residues of its 8 chain complementarity-determining region 3 (CDR3) loop to bind T22 in an orientation substantially different from that seen in alpha beta TCR/peptide-MHC. That junctionaily encoded G8 residues play an ancillary role in binding suggests a fusion of innate and adaptive recognition strategies.