Immunologists often try to obtain high affinity peptides by mutating one or two positions of an interested peptide. Such peptides are often called heteroclitic. Amino acids at these positions are substituted with up to 20 different amino acids and the affinity of the new peptides are tested experimentally. This server provides a computerised approach to the design of heteroclitic peptides, using the additive method to calculate affinities. The server accepts as input one nonamer peptide sequence (or one octamer peptide for H-2Kb and K-2Kk). The user can then choose to change either one or two random positions of the peptide. Affinities of the new peptides are calculated and displayed in the results page, with the original peptide highlighted in red.

3 cut offs are available:
1) affinities greater than the IC₅₀ of the original peptide
2) affinities greater than 5% lower than the original peptide
3) or all peptides generated.