An isolated epitope comprising X1-X2-X3-X4-X5, wherein the binding of a ligand to the epitope on activated T cells induces cell death, and X1 is Tyr, Trp, His or Met; X2 is Asp; X3 is Ser, Phe, Pro, Glu or His; X4 is any amino acid; and X5 is Pro, Tyr, His or Trp, and also where the epitope is not SEQ ID NO: 5.Un epítopo aislado que comprende X1-X2-X3-X4-X5, en donde la fijación de un ligando al epítopo sobre células T activadas induce la muerte de las células, y X1 es Tyr, Trp, His o Met; X2 es Asp; X3 es Ser, Phe, Pro, Glu o His; X4 es cualquier aminoácido; y X5 es Pro, Tyr, His o Trp, y además en donde el epítopo no es SEQ ID NO:5.