Peptide selection by MHC class I molecules

Abstract

SYNTHETIC peptides have been used to sensitize target cells and thereby screen for epitopes recognized by T cells1–7. Most epitopes of cytotoxic T lymphocytes can be mimicked by synthetic peptides of 12–15 amino acids8. Although in specific cases, truncations of peptides improves sensitization of target cells8,9, no optimum length for binding to major histocompatibility complex (MHC) class I molecules has been defined. We have now analysed synthetic peptide captured by empty MHC class I molecules of the mutant cell line RMA-S. We found that class I molecules preferentially bound short peptides (nine amino acids) and selectively bound these peptides even when they were a minor component in a mixture of longer peptides. These results may help to explain the difference in size restriction of T-cell epitopes between experiments with synthetic peptides and those with naturally processed peptides10–12.