Recognition by CTL clone JL12 of HLA B*3501⁺ PHA blasts with the addition of monosubstituted peptide analogs of KPIVVLHGY. Every one of the 20 genetically coded amino acids was tested in each of positions 6, 7, and 8 within the parent sequence KPIVVLHGY. The letter within each graph represents the parent residue being replaced; the horizontal axis lists the residue replacing the parent residue. Three different peptide concentrations were used (200 μmol/L [▪], 2 μmol/L [], and 0.02 μmol/L [□]) and the E:T ratio was 2:1.