PEPTIDE SELECTION BY MHC CLASS-I MOLECULES

SYNTHETIC peptides have been used to sensitize target cells and thereby screen for epitopes recognized by T cells 1-7. Most epitopes of cytotoxic T lymphocytes can be mimicked by synthetic peptides of 12-15 amino acids 8. Although in specific cases, truncations of peptides improves sensitization of target cells 8,9, 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 peptides 10-12.