Purified MHC class I molecules present hapten-conjugated peptides to TNP/H-2Kb-specific T cell hybridomas.

Several trinitrophenyl (TNP)-specific mouse cytotoxic T cell (CTL) clones recognize TNP-conjugated peptides in association with class I MHC Kb-molecules. Here we show that CD8+ T cell hybridomas derived from these CTL exhibit the same pattern of antigen-specificity as their parent CTL-clones. These T cell hybridomas reacted with TNBS- or TNP-peptide modified syngeneic target cells, and also with affinity purified, immobilized Kb-molecules preloaded with TNP-peptides. These findings demonstrate most directly that MHC-associated, haptenated peptides create functional antigenic epitopes for TNP-specific CTL. Furthermore, using purified Kb-molecules and a panel of Kb-binding TNP-conjugated peptides, we demonstrated that the epitope density is a critical factor in triggering these T cell hybridomas. Chemical modification of immobilized Kb-layers resulted in poor antigenicity, implying low epitope density and therefore arguing against covalent MHC-haptenization as a major source of T cell antigenic determinants.