CHARACTERIZATION OF A SINGLE-CHAIN ANTIBODY TO THE BETA-CHAIN OF THE T-CELL RECEPTOR

In this report the V-H and V-H genes of the anti-T cell receptor (TCR) antibody KJ16, which recognizes the TCR V beta 8.1 and V beta 8.2 reg ions in mice, were cloned and expressed as a single-chain antibody (sc Fv) in Escherichia coli. A 29-kDa protein was obtained after renaturat ion from inclusion bodies. The KJ16 scFv bad a relative affinity for t he native TCR that was slightly higher than KJ16 Fab fragments. The sc Fv and Fab fragments of the KJ16 antibody, together with monovalent fo rms of two other anti-TCR antibodies, were evaluated as antagonists of the T cell-mediated recognition of a peptide-class I complex or of a superantigen. Staphylococcus enterotoxin B (SEB) bound to a class II p roduct. Each of the anti-TCR antibodies was efficient at inhibiting th e recognition of the SEE-class II complex. In contrast, only the clono typic antibody, which binds to epitopes on both the V beta and V alpha regions, inhibited the recognition of peptide-class I complex. We con clude that the TCR binding site for the SEB-class II ligand encompasse s a larger surface area than the TCR binding site for the peptide-clas s I ligand.