Immunobiological Analysis of TCR Single-Chain Transgenic Mice Reveals New Possibilities for Interaction between CDR3#alpha# and an Antigenic Peptide Bound to MHC Class I

摘要

The interaction between TCRs and peptides by MHC molecules determines the specificity of the T cell-mediated immune response. To elucidate the biologically important structural features of this interaction, we generated TCR #beta#-chain transgenic mice using a TCR derived from a T cell clone specific for the immunodominant peptide of vesicular stomatitis virus (RGYVYQGL, VSV8) presented by H-2K~b. We immunized these mice with VSV8 or analogs substituted at TCR contact residues (positions 1,4, and 6) and analyzed the CDR3#alpha# sequences of the elicited T cells. In VSV8-specific CTLs, we observed a highly conserved residue at position 93 of CDR3#alpha# and preferred J#alpha# usage, indicating that multiple residues of CDR3#alpha# are critical for recognition of the peptide. Certain substitutions at peptide position 4 induced changes at position 93 and in J#alpha# usage, suggesting a potential interaction between CDR3#alpha# and position 4. Cross-reactivity data revealed the foremost importance of the J#alpha# region in determining Ag specificity. Surprisingly, substitution at position 6 of VSV8 to a negatively charged residue induced a change at position 93 of CDR3#alpha# to a positively charged residue, suggesting that CDR3#alpha# may interact with position 6 in certain circumstances. Analogous interactions between the TCR #alpha#-chain and residues in the C-terminal half of the peptide have not yet been revealed by the limited number of TCR/peptide-MHC crystal structures reported to date. The transgenic mouse approach allows hundreds of TCR/peptide-MHC interactions to be examined comparatively easily, thus permitting a wide-ranging analysis of the possibilities for Ag recognition in vivo.