Abstract: Compounds having immunomodulatory activity which are peptide-type compounds, or variants or fragments thereof, including the N-terminal acylated and C-terminal amidated or esterified forms of up to 30 amino acids wherein the peptide-type compound comprises the formula: (a) R aa76-77 L aa79-84 or (b) aa84-79 L aa77-76 R wherein: aa76 is E or V; aa77 is D, S or N; aa79 is R or G; aa80 is I or N; aa81 is a small or hydrophobic amino acid aa82 is R or L; aa83 is G or R; aa84 is a small or hydrophobic amino acid; wherein, in said compounds, at least one of the amino acids is the D isomer are used by themselves or in combination with immunosuppressant drugs, to reduce CTL activation, particularly in association with transplantation.