Induction of peptide-specific CD8+ CTL clones in beta 2-microglobulin-deficient mice.

We have examined the ability of beta 2-m- mice to produce CD4-8+ T cells by generating CD8+ CTLs to a defined ligand. We report here the first demonstration of peptide-specific, self-class I MHC-restricted CTLs from beta 2-m-deficient mice. We have used the KOD mouse, an H-2d beta 2-m- strain, to generate CTLs that recognize the class I MHC molecule Ld in association with one of two Ld-binding immunogenic peptides. Testing of these CTLs on a panel of Ld-binding peptides reveals a high degree of peptide specificity. Peptide-specific CTL bulk cultures from KOD mice differ from those generated in beta 2-m+ mice in that they possess altered affinities for their peptide ligands. In addition, we show that CTLs generated from beta 2-m- mice in the presence of beta 2-m+ stimulator cells and exogenous peptide are specific either for the exogenous peptide or for endogenous peptides that are present in association with Ld on the surface of beta 2-m+ cells, but are not present at detectable levels on beta 2-m- cells. These results demonstrate that positive selection of CD8+ CTLs can occur in vivo on the very low levels of class I MHC found in the KOD mouse. Furthermore, CTLs from the KOD mouse maintain a high degree of peptide specificity despite reduced levels of class I MHC.