Specificity of soluble 2c tcr/ig superdimers for peptide/MHC complexes

To study expression of specific peptide/MHC complexes we have developed an high avidity soluble analog of the 2C T cell receptor (soluble TcR superdimer). The avidity of the TcR for it's cognate was increased by genetically engineering a divalent, soluble version of the 2C TcR. This was done by ligating the extracellular domains of the TcR α and β chains to murine cDNA encoding Ig heavy and light chains. Using flow cytometry, soluble 2C TcR/Ig superdimers specifically bound to H-2L^d molecules loaded with peptides known to interact with the 2C TcR (p2Ca, QL9, and SL9). Variants in the p2Ca peptide, which have previously been characterized in terms of their ability to mediate lysis and bind to soluble monovalent 2C TcR¹, were also studied. Soluble 2C TcR/Ig superdimers bound to most of the p2Ca variant peptides that mediated lysis. While some of these peptides had been shown to interact with monovalent 2C TcR, others, that mediated lysis, did not have demonstrable binding in a plasmon resonance based assay¹. Thus, a flow cytometry based assay using soluble TcR superdimers was more sensitive at probing the structure of the peptide/MHC complex. Using soluble 2C TcR/Ig superdimers we will be able to characterize the affinity of variant peptides for TcR and gain insight into the mechanism of T cell activation and peptide-based antagonism.