Structure function analysis of the interaction of class I MHC, peptide and T cell receptor

Abstract

The interaction of the class I major histocompatibility molecule (MHC) with peptide antigen and T cell receptor is essential for the cytolytic T lymphocyte (CTL) response to foreign antigen. This thesis describes an experimental approach designed to elucidate the structural and functional characteristics of murine class I MHC which facilitate this interaction.;The structural effects of the altered amino acids in the K{dollar}\sp{lcub}\rm b{rcub}{dollar} protein of the mutant bm1 mouse were analyzed using an in vivo experimental system. The K{dollar}\sp{lcub}\rm bm1{rcub}{dollar} molecule differs from K{dollar}\sp{lcub}\rm b{rcub}{dollar} at three residues resulting in the lack of CTL response to a variety of viral challenges. The effect of each amino acid change on the bm1 immune response was analyzed with single point K{dollar}\sp{lcub}\rm b{rcub}{dollar} mutant transgenic mouse lines.;Allogenic cytolytic T lymphocyte recognition of the transgenic molecules by bm1 mice was demonstrated, suggesting that the changes at both positions 152 and 155 significantly altered the interaction of class I molecules with peptide and T cell receptor.;Analysis of the cytolytic T lymphocyte (CTL) response in the transgenic mice expressing the K{dollar}\sp{lcub}\rm b{rcub}{dollar} mutant molecules revealed a difference in the effect of the altered residues at positions 152 and 155. Expression of the transgene mutated at position 152 in bm1 mice restored the CTL response to Sendai virus, however expression of the transgene mutated at position 155 in bm1 mice failed to restore this response. Both transgenic molecules served as Sendai presenting molecules to K{dollar}\sp{lcub}\rm b{rcub}{dollar}-restricted, Sendai-specific CTL, indicating that the lack of CTL response in the bm1-155 transgenic mice was not due to a presentation defect. These data suggest that bm1-155 lacked the ability to select a T cell repertoire which included Sendai specific CTL. Selection of Sendai CTL occurred in bm1-152 mice indicating that the defect was due not to negative selection by K{dollar}\sp{lcub}\rm bm1{rcub}{dollar}, but to a lack of positive selection by either K{dollar}\sp{lcub}\rm bm1{rcub}{dollar} or K{dollar}\sp{lcub}\rm bm1-155{rcub}{dollar}. Our evidence suggests that residue 155 in the K{dollar}\sp{lcub}\rm b{rcub}{dollar} molecule plays a critical role in the selection of the T cell repertoire and that alteration of that residue in the bm1 mouse results in the lack of positive selection of Sendai virus specific CTL.